TECH TIPS

QUESTIONS AND ANSWERS email roger@vincicams.com

These tips are a compilation of facts from legendary Roger Vinci and other leading valvetrain experts.
We sincerely hope you can benefit from this information.
 

                           CONTENTS
Valve Train "101" A Series of Informative Articles Introduction
Article 1 Power Improvements Associated with Quality Aftermarket Rockers.
Article 2 What to Look For In Good Quality Aftermarket Rocker Arms.
Article 3 Stud Rockers Or Shaft Rockers / Which ones to use?
Article 4 The True Cost of Valvetrain \Setups. Stud Mount vs. Shaft Mount vs. Full Shaft systems
Article 5 Myths About Rocker Arm Weight and Valve Float.
Article 6 Pretty Doesn’t Always Indicate Good – Buyer Beware, Anodized Rockers Hide a Lot of Shortcomings.  
Article 7 Cast, Vs Billet Aluminium, Vs Steel Rockers.
Article 8 Why Is It Important To Ask Where Your Rockers Are Manufactured And By Whom?
Article 9 Rocker Arm Geometry- made easy!
Article 10 Rocker Clearances- What Critical Areas To Inspect?
Article 11 What Causes Valve Float and How To Identify It.
Article 12 What Failures Can One Expect From Improper Rocker Geometry?
Article 13 Valvetrain Noise / Probable Causes & Checks.
Article 14 Rocker Breakage! What Typically Causes It – Too Much Spring Pressure, Bad Geometry, Wild Camshafts?
Article 15 Impacts of Harmonics on High Performance Valvetrains
Article 16 Roller Rocker Ratios- What Does a Ratio Change Actually Do?
Article 17 The Value Of Mixed Rocker Ratios.
Article 18 What Oils Should Be Used for Performance Valvetrains? (proper camshaft, lifter, rocker break-in procedures)
Article 19 The Effect of Temperature On Cams and Rockers.
Article 20 Lifter Preload - Take The Guesswork Out of Preload Adjustment.
Article 21 Roller Rocker Adjustments-How Often, When and How
Article 22 Street Rockers / Street - Race Rockers / Race Only Rockers: Which ones to use?
Article 23 Adjustable Vs. Non Adjustable - What Rocker & Lifter Combinations Should be Used?
Article 24 Innocent Until Proven Guilty - Hi-RPM Power Failures Attributed to Roller Rockers
Article 25 Methods of Reducing Friction in the Valvetrain
Article 26 Inspection and Servicing Yella Terra Rocker Arms

MORE VALVETRAIN TIPS
Why Leading Cam Manufacturers Measure “Advertised Duration” at .004” Lifter Rise
How To Compare Duration Specs Between Pushrod Cams and OHC!
Rocker Arm Geometry
Lofting
Ignition Timing vs. Valve Timing
WHAT EXACTLY IS "LSA" OR LOBE SEPARATION? HOW DOES IT AFFECT THE POWER CURVE?
Cam Timing
Rocker Ratio
Valve spring height. Does it matter?
Timing Chain Alignment
TRUCK TECH TIP
Which VHP / Crane Lifter Do I Use?
New "Premium" LS1/LS6/LS3 Dual Valve Spring, # VHP-HD-SK       New "Extra Premium" LS1/LS3/L92 Dual Valve Spirng # VHP-XD-Sk
Can Rocker Arm “Weight, Mass, and Moment of Inertia Lead To Valve Float?
CAM RETAINER PLATE WEAR
The Right Way To Use Adjustable Checking Pushrods to Determine Correct Pushrod Length
Coil Bind
More On Why Our Unique New “Accelerated Lift” Rocker Arm Geometry Makes More HP!
Most Important Vehicle Factors in Selecting a Camshaft
Quality Steps. . . Or How Lobe-to-Lobe Accuracy Affects HP And Durability!
Is Choosing The Right Valve Springs for Supercharged Engines Critical?
NEW HANDHELD DIAGNOSTIC TUNER TIPS
CLUTCH SHIELD INSTALLATION INFORMATION TIPS
Extra Cylinder Pressure A Good Thing?
FUEL STARVATION ISSUE
Proper Coolant Temperature and Camshaft Life!

ROCKERNOMICS

Valve Train "101" A Series of Informative Articles
by Roger Vinci
 

Article 11 in the Yella Terra “Rocker Arms 101” Series

What causes valve float and how to identify It?

    Just what is valve float?

“Valve float” is a common term for a situation best described as (valve train separation). This occurs due to inertia load imparted into the valve train by the action of the cam lobe against the follower. Weak valve springs are among the most common causes of valve float. Fast lobe profiles, heavy valves, etc force the need for high quality springs with increased pressure. That said, too much pressure can be disastrous to rocker arms and is often unwarranted. Forced induction is another contributor to “valve float”. Because of the increased pressure on the face of the valve, stronger springs are usually warranted.

Flex in the valve train (the majority of which is located in the pushrod) is a prime contributor to valve train separation or “valve float”. The initial loads imparted into the pushrod cause it to bend (somewhat like a pole vaulter’s pole) and then return to a straight configuration. This unloads a sharp energy pulse to the rocker arm, which transfers it into the valve/valve spring assembly. This often results in “valve lofting,” which causes the valve to operate in a different path than that described by the lobe profile. At the same time, the lifter without any load against it, can also be launched off the opening ramp of the lobe and then, as load is re-established, either: strike the nose of the lobe and eventually damage it; land on the closing ramp (like a ski jumper landing on the slope of a hill); or land on the base circle with significant and often damaging impact. If “lofting” can be controlled (by design or good fortune and the lifter lands gently on the closing ramp), it adds to area under the curve and more power. If it is uncontrolled (which happens the vast majority of the time), it can be damaging to valve train components and will compromise performance. Most of the time, power flattens out or is lost when valve train separation occurs. Again, the biggest culprit in causing this situation is the flex of the pushrod.

Many people on website forums tend to think that the “weight” of the rocker arm is the cause of “valve float”. If the rocker is rigid and properly designed, it should contribute very little to “valve float”. Weight in this case is not the prime issue, but rather the “moment of inertia” of the rocker design. “Moment of inertia” is the affect of where the mass of the rocker arm is located relative to its center of rotation. One rocker can be much heavier than another and still have a smaller moment of inertia because of where its mass is located; so weighing rockers to determine their affect of valve float is really not effective at all. (FYI: “mass” is a measure of a body’s inertia; while “weight” is the affect of gravity on “mass.” “Moment of inertia” is unaffected by weight, but is affected by where “mass” is located relative to the center of rotation!). The highest quality aftermarket rocker arms are designed to be rigid (to minimize flex), and have a very low moment of inertia relative to the necessary strength.

Other issues are often misdiagnosed as “valve float”. These issues can mask themselves and give the impression of “valve float”.

11  1. Coil Bind.
Increased lift causes the clearance between the valve spring coils to diminish. The spring can become solid. The minimum recommended clearance is .060”.   
2. Additional lift can cause the pushrod to travel a different arc. The position of the pushrod in the rocker arm cup and or additional lift can reduce the clearance between the pushrod and the cylinder head. If the pushrod contacts the head during its rotation, it can stall momentarily causing the lifter to expand and pump up, holding the valve open temporarily. The result manifests itself exactly like “valve float”.
3. Proper rocker arm clearance, that is, something interfering with the ability of the rocker to make its full sweep can manifest itself as “valve float”. Clearance should be checked throughout the entire sweep of the rocker arm. The minimum recommended clearance is .60”

 Understanding the issues surrounding the phenomenon of valve train separation is paramount in identifying the problem and correcting it. To ensure consistent performance and safety throughout the entire range the engine operates in, valve float must be controlled. Unchecked, valve float can and usually does, contribute to engine destruction.  

Article 12 in the Yella Terra “Rocker Arms 101” Series

What failures can one expect from improper rocker geometry?

If the rocker arm contact patch is too far towards intake or exhaust side or operating in too large of an arc, creating a wide contact patch, severe rocker arm side loading can result. Here is a list of the possible failures that can result.

1. Severe, premature, valve guide wear.
2. Premature valve stem wear.
3. Premature valve tip wear.
4. Nose wheel failure.
5. Valve stem failure at keeper grooves.
6. Uneven valve seat wear.
7. Premature valve spring fatigue.

 Improper rocker geometry allowing the rocker arm to run “off center” of the valve stem tip, towards front or rear of engine can cause the following failures.

1. Pushrod tip or cup wear.
2. Pushrod cup or adjuster wear in rocker arm.
3. Pushrod guide wear.
4. Cylinder head - pushrod hole wear.
5. Rocker stud or hold down bolt wear.
6. Poly lock wear at trunion seat area.
7. Rocker trunion at poly lock seat area wear.

 Improper clearances in any of the vital areas mentioned in article 10 can cause the following failures.

1. Rocker arm fulcrum and bearing wear.
2. Rocker stud or mounting bolt wear or breakage.
3. Valve spring retainer “outside diameter” wear.
4. Rocker arm wear at underneath area adjacent to retainer.
5. Valve spring retainer adjacent to valve seal.
6. Valve seal failure.
7. Valve guide wear at seal boss.
8. Rocker arm body near cylinder head contact points.
9. Rocker arm failure from valve spring coil bind.
10. Rocker arm failure from improper valve to piston clearance.

To avoid these failures and to ensure proper performance and longevity for your engine, always make the effort to check and correct any rocker arm geometry issues. Manufacturers of high quality aftermarket rocker arms have engineered the rockers with all of these parameters in mind, but, it is always up to the installer to properly check and fit any and all aftermarket products.

Article 13 in the Yella Terra “Rocker Arms 101” Series

Roller Rocker / Valvetrain Noise Probable Causes & Checks
 

Some valvetrain noise is to be expected when moving to a high quality set of roller rockers. There are over 500 needle bearings in most roller rocker kits. Often they emit a ”sewing machine” type noise, which is harmless and quite normal. On the other hand, loud clicking, knocking, snapping or squeaking sounds are not to be tolerated. All of these sounds indicate the possibility of a serious failure is in the works.

 Valvetrain noise can be caused by many improprieties. Improper rocker geometry, for instance, allowing the rocker arm to run off center of the valve stem tip towards the front or rear of engine can cause the rocker nose wheel to rattle against the valve tip. It can also cause the pushrod to enter the rocker at a severe angle forcing it to pop around in the rocker cup or contact the pushrod guideplate or cylinder head. Improper geometry can cause the rocker fulcrum to rattle against the poly lock, a problem with many stud mount rockers.

Valvetrain noise should not be associated solely with roller rockers as the most obvious culprit. Many other issues can cause noises that manifest themselves as roller rocker noise.

Insufficient clearance around the pushrod can cause contact with the head, which causes the pushrod to loose contact with the hydraulic lifter allowing the lifter piston to momentarily expand which in turn makes a clicking noise.

Too short a pushrod can cause the rocker to sit lower on head and contact the stud boss.

Insufficient clearances can allow rockers to come in contact with other parts of the valvetrain as well. These are, but not limited to, proper clearance between rockers and valve cover and cylinder head rails.

Too little preload can cause hydraulic lifter noise. Worn lifter bores in the block, as well as worn lifter id bores or dirty or leaky lifters can cause valvetrain noise.

Extreme camshaft ramp speeds can also cause valvetrain noise, as the lifter has difficulty maintaining contact with the camshaft lobe. Aggressive or poor cam lobe designs or opening ramps with high acceleration rates can literally hammer the valvetrain parts. The noise is similar to that of a hammer banging on an anvil, not good. Closing ramps that are too abrupt essentially allow the lifters to drop onto the base circle of the cam lobe with sever force, also not good. Closing ramps should be designed to slow the valve down as it closes and set it gently on the valve seat.

 Loose or worn camshaft bearings can allow the cam to rattle around in the block. Cam bearings should be checked for concentricity and size when cams are installed. Loose cam bearings are a common source of oil pressure loss.

Loose timing chain sets can emit noises that are frequently diagnosed as valvetrain noise.

 Stiff, high pressure valve springs magnify noise sources in the valvetrain. Couple this with poorly designed, aggressive cam profiles and the result is dangerous valvetrain loads and irritating, destructive noises.

 Careful examination of the aforementioned information will lead to a quieter, safer, engine with longevity being paramount.
 

Article 16 in the Yella Terra “Rocker Arms 101” Series

Roller Rocker Ratios- What Does a Ratio Change Actually Do?

First an explanation of what rocker ratio is and its significance. Rocker arm ratio is the ratio of the distance from the rocker arm's center of rotation to the tip divided by the distance from the center of rotation to the point acted on by the camshaft or pushrod. Valve lift is determined by the combination of the cam lobe lift and the rocker arm ratio. A rocker arm ratio of 1.8 means that the actual cam lobe lift will be multiplied by 1.8. For example, a cam lobe lift of .347” (times) rocker ratio of 1.8 equals .625”.
Engine builders have consistently seen significant power increases with the right aftermarket rocker and cam combinations. Higher ratio rockers are the choice of most of the contestants in the Engine Masters Challenge, running rocker ratios in the 2:1:1 category, year after year. Increased ratio rockers produce more lift out of a given cam profile. They also lift the valve off the seat at a much faster rate than stock rockers to initiate and sustain increased airflow. Higher ratio rockers can also increase horsepower and torque rather than hurting torque, lowering vacuum, and reducing idle quality. Increased ratio rockers limit the lifter travel which reduces internal friction and lifter / pushrod inertia. This in turn can allow for the use of lighter valve springs due to the increased leverage effect of the high lift rocker arm upon closing the valve.

When changing rocker arm ratios on your engine to a higher ratio, not only does the gross valve lift increase, but the duration at the valve in the higher lift ranges also grows. Because the increased ratio effectively speeds up valve movement the valve will reach any opening height sooner than it would with a lower ratio rocker arm. Higher ratios open the valves quicker and close the valves a little later. Since the increase is symmetrical on either side of the cam lobe centerline, a higher ratio will lengthen the overall valve timing making your cam act bigger. The effective valve open duration can be extended as much as 3 to 4 degrees, depending on the cam type, as measured at .050″ cam lift, when the ratio is changed from 1.7 to 1.8. While the valve lift increases but begins the lift at the same point, the opening and closing rates are steeper. This results in the valve reaching the .085” lift point (.050×1.7) earlier and effectively increasing duration. In fact the duration or time the valve is in motion from seat to seat does not change. The valve starts to move and stops moving at the same time as with a lower rocker ratio, (Hydraulic zero lash valvetrain.) but it does move faster and farther relative to cam lift or lifter motion. The effect on the valve is like adding extra degrees of duration. The cam specs don't change, nor does the actual valve timing but the valve motion does change. The higher ratio causes valve timing to increase proportionally as the valve opens further. Benefits of this geometry include increased flow into the cylinder earlier in the cycle, quicker closing of the valve to trap cylinder pressure before combustion, more effective duration at .200" net valve lift, while maintaining a relatively short seat-to-seat timing, and less required valve spring seat pressure because of the mechanical advantage of the higher seat ratio. In most dyno tested engines that had a quality set of aftermarket roller rockers installed, the power increases are quite significant. Horsepower figures increase, on average, about 14hp with same ratio rocker replacement and 25hp with higher ratio rockers. Torque figures are increased, as well, with stock ratio rockers producing an additional 12 ft lbs torque and higher ratio rockers producing 20 on average.

The rocker ratio can change due to plasticity, that is, the capability of the rocker arm material not being able to withstand the rigors of aggressive lobe profiles and higher spring pressures. The rocker arm can actually deflect during the lift cycle which reduces the effective ratio. This result is the rocker failing to reach full lift. It is very important to ascertain the material your rocker arm choice is made from. Inexpensive cast and or stamped rocker arms just won’t cut it when you exceed the factory specs with aggressive cam profiles or high spring pressures, Always opt for a high quality billet aluminum or steel rocker arm to insure proper geometry and valvetrain longevity.

 Other areas of concern are the trunion and trunion bearings. They must be extremely strong and the fit must be held to tight tolerances, to insure the rocker arm can operate through its full cycle without lost motion. Factory rockers with flimsy or worn trunions and bearings are guilty of this action.
Not to further confuse the issue, but another important note is that the rocker arm ratio is always changing because the rocker arm tip is moving on an arc around it's center pivot point, but the valve stem goes straight up and down. This means that as the rocker arm moves, the distance from the pivot point to the contact point on the valve stem is always changing. If this distance is changing, the rocker ratio is also changing. Typically, the amount of change for a nominal 1.7 rocker ratio in a pushrod engine is from 1.65 to 1.75 as it goes through its arc. This is one more reason to increase rocker arm ratio, to help offset the lower end ratio effect.

There are some possible negative effects and cures that must be considered when using higher ratio rocker arms.  Higher ratios put a greater load on the pushrods! Therefore, stiffer pushrods should always be used in conjunction with higher ratio rocker arms. Higher rocker ratio rockers move the pushrod cup closer to the trunnion of the rocker causing possible interference issues with some cylinder heads. Increased rocker arm ratios increase gross valve lift, which in turn reduces spring coil bind clearance, retainer to seal clearance and piston to valve clearance.  To prevent negative effects, ensure all valve train clearances are sufficient to support the higher ratio rocker system.

 

Article 17 in the Yella Terra “Rocker Arms 101” Series

The Value of Mixed Rocker Ratios

The debate over the optimum rocker-arm ratio has dragged on probably since the invention of the pushrod V-8. One important factor is, factory engine manufacturers generally build their rockers with a less than advertised in true rocker ratio. That is to say, a typical factory rocker arm rated at 1.7 to 1 when measured with a dial indicator can actually be less than advertised. I have seen them as low as 1.66 to 1. Utilizing a quality aftermarket roller rocker system can bring the ratio back to advertised ratio or increase it on the intake and / or exhaust side.

A terrific tuning aide many engine builders and tuners consistently use is testing an engine’s combination performance by mixing rocker arm ratios. It is considerably easier to swap rocker arms than camshafts. Some engine combinations respond very favorably to added lift on the intake or exhaust side of the engine. Often with stock heads even ported, the exhaust side really doesn’t flow as well as it should. The inlet and exhaust paths are viewed as a restriction to the cylinder and the flow capability varies depending on the cross-section and bowl geometry. A cylinder is a displaced volume that sees flow movement and accelerations based on the stroke, bore, and rod geometry. One can run either a dual pattern cam with more lift on the exhaust side, or higher ratio rockers on the exhaust side. In many cases, the exhaust side needs a chance to get rid of the combusted charge and help start the intake flow into the cylinder. Additionally, a dual pattern cam that is heavily biased to the exhaust with wider and earlier events can be balanced out a little bit with the larger ratio on the intake. This would be very advantageous in a lower intake capability motor that does not need all the exhaust flow capability and it could just as easy be effective on single (or similar) pattern camshaft too. It all depends on the particulars of the specific combination. As far as rocker arm ratios are concerned, there are no rules set in stone. Every case has to be analyzed on its own.

On supercharged or nitrous assisted engines, many tuners have profited from running a higher lift on the exhaust rocker, than the intake. Because the intake side of modern engines is generally more efficient than the exhaust side and the supercharger or nitrous charge is being forced into the combustion chamber, there is a far greater demand to rid the chamber of the spent charge to make room for the incoming charge. While a cam change may very well be in order, a rocker arm ratio change is simple, effective, far less costly and time consuming. If the results are positive, a cam change would probably be called for.

Some of the more savvy manufacturers understand the value of mixed rocker ratios and actually offer rocker arms in half sets to enable the engine builder to comfortably create mixed ratio sets.

Article 18 in the Yella Terra “Rocker Arms 101” Series

What oils should be used for high performance valvetrains?
Are there different oils recommended for Flat Tappet and Roller applications?

 Lubrication! Your engine can’t live without it. There are very different theories when it comes to which oil should be used with flat tappet cams and roller camshafts. While some agree to disagree, the following facts are pretty well unanimously accepted in the performance industry today.

When dealing with flat tappet cams, an extremely high quality break-in oil is imperative to allow proper break- in. Never, use a “multi vis” or synthetic oil for break-in purposes with flat tappet cams. Flat tappet cams must have high quantities of the anti-scuffing additives Zinc and Phosphorus to counteract the forces of metal to metal contact that prevent the proper break-in sequence. The recent government required reductions in these additives in standard oils present serious problems for flat tappet camshafts. Yesterday’s oils had much larger quantities of these additives which helped enormously in the break-in procedure. The Zinc and Phosphorus content in today’s “off-the-shelf” oils have been reduced upwards of 20% since 2001 and approximately 35% since 1997). In terms of oil selection, manufacturers recommend a high “ZDDP”, Zinc Dialkyl Dithiosphosphate, content oil for the break-in procedure and regular operation. There are several companies that are now offering specialized “race/off-road” oils, high in anti-friction and anti-wear content, to combat this specific problem. These oils carry the SL rating and contain up to 1000 ppm of Zinc and Phosphorous.

There are very articulate methods for break-in procedure camshaft manufacturers demand today to ensure the camshaft and lifters mate properly. Many manufactures insist on the use of very light valve springs during the procedure and then replacing them with the recommended stiffer springs when the break-in procedure is completed. Lifters should not be prefilled with oil, as this tends to hold the valves open which requires additional time to start the engine. The camshaft and lifters must be coated with a special break-in paste assembly lube recommended by the manufacturer. This paste contains extremely high quantities of Lithium Molybdenum Disulfide, an anti wear compound packaged in most flat tappet cam kits. Care should be taken to rotate the engine as few times as possible to ensure the coating stays on the cam and lifters. The oil pump should be primed. Timing should be pre-set and carburetors pre-filled with fuel, to eliminate unnecessary engine rotation during startup. Once the engine is started, it should be revved up to 3000 rpm “quickly” and varied from 1500 to 3000 rpm continually for 30 minutes. The increased, oscillating rpm provides adequate oiling of the cam and lifters while ensuring a ” lean-out” condition does not occur from holding the engine at a constant high vacuum rpm.  Be sure the timing is advanced adequately to prevent excessive engine loading and heat during the break-in procedure.

Once the procedure is finished, the break-in oil should be drained, filter changed, and a high quality 30wt non synthetic oil put back in the engine. Next the proper tension valve springs should be installed. After 500 miles the oil and filter should again be changed. At this time a high quality non synthetic oil with a viscosity rating of not less than 10w 40 should again be used. Most flat tappet cam manufacturers do not recommend using synthetic oils at any time. Not following a proper break-in procedure will surely cause premature camshaft / lifter failure, and most manufacturers will not warranty an improperly broken in camshaft.

When dealing with roller camshafts and roller lifters, special break-in oil is unnecessary since no break-in is required. The same applies to roller rockers. On non-catalytic converter applications, use petroleum based SE, SF, SG grade, oil. On catalytic converter applications, use a premium, petroleum based oil, with a viscosity rating of not less than 10w 40. An API rating of SL or SM is required. Be sure to fill the new oil filter with oil before installing it. .

No break-in paste type compounds, like the ones used with flat tappet cams, should be applied to the roller camshaft, or roller lifters, just a formidable amount of the same high quality oil used in the engine. The pushrod cups in roller rocker arms and valve stem tips should be coated with a lithium molybdenum assembly lube to help alleviate scuffing during initial start up, while lifters and pushrods are filling with oil.  An ample supply of a premium, petroleum based oil, with a viscosity rating of not less than 10w 40, should be used to lubricate the roller lifters, and roller rocker arms. Again, most roller cam and roller rocker arm manufacturers so not advocate the use of synthetic oil during the initial run-in period.

When first starting the engine hold the rpm to a fast idle while lifters are filling. It is not uncommon for the lifters to require proper filling and emit some noise during the initial start-up. I have found that running the engine for a few minutes and then shutting it down for 10 minutes will often allow the lifters to bleed and balance themselves. Upon restart, the loose lifter noise is usually gone. Any performance engine equipped with a roller cam and / or roller rockers should be treated with the very best oil one can afford. Change oil and filter regularly. Heavier weight oils tend to quiet the sometimes sewing machine noise associated with roller rockers and do afford more protection than lighter weight oils.

Most roller rocker arm manufacturers do not advocate the restriction of oil to the top of the engine, a practice of many engine builders. This procedure not only restricts lubrication to the rockers, but also under high stress conditions oil directed from the rocker arms splashing on the valve springs has an important cooling effect on the springs. Restricting the oil supply to the valvetrain can interfere with this process. My advice, be cautious when limiting the oil supply anywhere in your engine. When in doubt, seek the advice of the manufacturer.

Article 19 in the Yella Terra “Rocker Arms 101” Series

Rockers and Cams- How do they behave in high temp environment?
 

 One major effect high engine temperature has on both, rocker arms and camshafts is the “valve lash” or clearance between the rocker arm and the tip of the valve, associated with solid lifter type valvetrain. Engine temperature will alter the clearance between the valve tip and rocker arm tip. Standard sliding type of rocker tips associated with most production engines or aftermarket roller rockers with a roller nose wheel at the tip are subject to engine temperature changes. There is very little to be concerned about when the engine is equipped with hydraulic lifters as the amount of lifter preload far exceeds the range of clearance change from the increase or decrease in engine temperature.
This is not the case, however, with solid lifter camshafts. Depending on the block and head material as well as rocker arm material, the changes in valve lash can be quite significant. For instance when dealing with an iron block and iron heads, the valve lash can decrease by as much as .002” as the temperature increases from ambient to its normal operating temperature. Therefore the valve lash should be set .002 looser than the specifications call for. With an iron block and aluminum heads, the valve lash can increase, on average, by about .006” as the temperature increases from ambient to its normal operating temperature. The aluminum heads expand more than the iron heads. Therefore the valve lash should be set .006 tighter than the specifications call for. Care must be exercised because tightening the valve lash can reduce idle quality during warm up.

Article 21 in the Yella Terra “Rocker Arms 101” Series

Roller Rocker Adjustments – How Often, When and How?
Pushrods? Shims? Pedestals? Lash Caps?

This article will deal with adjusting the rocker arms solely for the purpose of acquiring lifter preload or valve lash. For an in depth explanation of rocker arm’s adjustment as it pertains to proper geometry, please see article no. 9 in the series,
“ Rocker Arm Geometry- Made Easy ”

Many owners who drive vehicles equipped with performance engines wonder how often they should adjust their roller rocker arms. There is no simple answer. Under normal driving conditions with hydraulic lifters and milder street style camshafts, further adjustments should be pretty much unnecessary. This is only true if the original adjustment included the proper lifter preload calculations. Occasionally a lifter will develop an internal wear problem causing it to emit a clicking noise. Frequently this can be alleviated by adjusting the preload a bit deeper with the rocker arm.  

Subjecting the rockers to increased spring pressures and / or aggressive cam profiles can cause them to loosen.  Quality aftermarket roller rockers are designed with high performance hazards figured into the equation to help prevent this from happening. Aggressive or poor cam lobe designs and / or opening ramps with high acceleration rates can literally hammer the rocker arms and other parts of the valvetrain. To help control this condition, engine builders usually move up to stiffer valve springs. While this tends to solve the immediate problem, other issues generally appear. Exceeding the manufacturer’s recommended, allowable spring pressure is a sure way to kill the rocker arms, or at the least, cause them to loosen up and allow the lifters to lose preload. This results in valvetrain noise which can often be corrected by re-adjusting the rockers.

Adjustable stud mount rockers utilize an adjuster nut or poly lock on the mounting stud to secure the rocker. While this system is perhaps the easiest to adjust lifter preload or valve lash, it is much less stable than shaft mount rocker systems and will not withstand the loads produced by today’s aggressive camshaft profiles or higher pressure spring sets.

When utilizing a shaft mount rocker system, appropriate installation techniques must be employed to ensure the proper function and longevity of the rocker system. Torque specifications must be followed to the tee, especially on newer alloy heads to guarantee hold down bolts remain tight and threads stay intact. High quality roller rockers manufactured from high quality ally extrusion such as 2024T6 are far less prone to losing their adjustment. Inferior rockers, specifically Asian made with inferior cast aluminum not only tend to lose their adjustment, but also cannot stand up to the rigors of today’s performance requirements. Beware of the “best bang for the buck theory”.  The “bang” may end up being emitted from your valvetrain.

There are many different concepts and styles of valvetrain hardware that cause a particular method of adjusting the lash or lifter preload to be followed. Besides the most common rocker adjustable styles, there are systems that utilize shims, lash caps, pedestals and pushrods to calibrate the proper valve lash or lifter preload. The pushrods are probably the most common method of adjusting lifter preload in hydraulic lifter systems, by altering their length. Longer pushrods create more preload and vice versa. Shims placed under rocker stands or pedestals in shaft mount rocker systems can be used to adjust lash but can also affect rocker geometry. The same applies to machining the stands or pedestals to shorten them. Rule of thumb suggests utilizing a roller rocker system that incorporates a threaded pushrod adjuster or cup adjuster to calibrate the valve lash, whenever possible. This type of system will have little effect on the rocker arm geometry, so long as the cup adjuster is kept within manufacturers specs. Care must be taken to follow manufacturer’s recommended allowable distance that the adjuster can be moved off the rocker seat to ensure the adjuster is not subjected to extreme loads. Generally two turns out from the seat is the maximum distance recommended by most manufacturers. Utilizing a proper length pushrod in combination with the rocker adjuster minimizes the stress on the adjuster. Many manufacturers provide light valve springs and adjustable pushrods to help facilitate proper lifter preload or valve lash.

In engines equipped with solid roller camshafts, the need for valve lash / rocker adjustment is more common. The constant pounding of the rocker against the valve stem causes shock and wear which imminently necessitates more frequent rocker adjustments.  Proper lash adjustment ensures maximum camshaft performance and valvetrain longevity.
Engine blocks or cylinder heads that have been surfaced or non factory head gaskets can alter the required lash or lifter preload measurements. Valve jobs tend to sink the valves deeper in the valve pockets, which increases the preload or reduces the lash.

Lash caps are little hats that fit over the valve stem. They are often used on SOHC and DOHC applications, which have no pushrods, to facilitate valve adjustment. On OHV applications “pushrod engines” they are not often used, however, one purpose is to increase the durability of the valve stem when using valves without hardened tips.  Another purpose is to lengthen the valves to achieve better rocker arm geometry when the valve stems are too short.  Here’s the catch. Lash caps add unwanted weight to the valve, as much as 10 to 15 grams. One should never add weight to the valve stem or rocker tip, if at all possible. It increases the likelihood of valve float, which necessitates the use of stiffer springs. Lash caps can and often do come off the valve stem. They have an uncanny ability of finding their way into the oil pan. Generally speaking, I never use lash caps unless there is no other way to correct a problem.

Article 22 in the Yella Terra “Rocker Arms 101” Series

 Street Rockers / Street - Race Rockers / Race Only Rockers
 which ones to use?

Definitions:

1)      Street Rocker
Generally, lowest cost rocker in the product line. Usually stud mount but some higher end manufacturers offer shaft mount rockers in a street style, requiring no special machine work or fitment. Should be constructed from quality alloy. Beware of imported, cheap cast replicas. Street rockers have a much lower spring pressure limit than race rockers but quality materials are always paramount.

2)      Street – Race Rocker
Generally higher cost rocker. Constructed from quality alloy extrusion. Can be stud mount but should have screw-in studs, guide plates and stud girdles. Shaft mount style rockers are considerably stronger, can handle higher spring pressures and more radical acceleration ramps.

3)      Race - Only Rocker
Generally top of the line rocker. Constructed from best alloy available. Shaft mount only to ascertain the stiffest integrity possible. Designed to handle the highest springs pressures and most extreme cam profiles.

When does the engine build demand the use of race only rockers? Let’s examine the parameters of a typical “street” build versus a “street - race” build versus a “race -only” build. Today, many “street” and /or “street - race” engines really should be classified as “race - only” builds. The stress caused by the extent of the modifications can move the classification from one level to the next.

Street Build: LS engine family
Engine bottom end is generally stock.
Heads are generally stock, occasionally aftermarket.
Maximum camshaft specs are in the area of .550” lift, 210* intake, 220* exhaust duration @ .050” lift, and the LSA runs between 116* and 114* with average acceleration ramps.
Spring requirements are in the area of 250lbs to 300lbs open pressure.
Rocker ratio is 1.7 to 1.85.
RPM operating range, 1,800 to 6,000 rpm.
This type of build can live a comfortably long life with most quality aftermarket street rockers, providing they are extruded and not cast Aluminum. In this application, full race top of line rockers can be overkill, but the Ching, Chang, Bang from imported rockers can often end up coming from your engine.

Street - Race Build: LS engine family
Engine bottom end is generally aftermarket with better rods and pistons, not uncommon for it to be bored and / or stroked.
Heads are generally ported, or aftermarket.
Maximum camshaft specs are in the area of .600 lift, 230* intake, 240* exhaust, @ .050” lift. LSA runs between 114* and 112*, with average to considerably faster acceleration ramps.
Spring requirements are in the area of 400lbs to 470lbs open pressure.
Rocker ratio is 1.7 to 1.85.
RPM operating range, 2,500 to 6,800 rpm.
This type of build can live a comfortably long life with high quality aftermarket stud or shaft mount street race rockers, providing the spring pressure does not exceed the stipulated spring pressure allowed by the manufacturer. In this application, full race top of line rockers can also be overkill, but entry level rockers can surely be “engine kill”.

Race - Only Build: LS engine family
Engine bottom end is usually forged, not uncommon for it to be bored and or stroked.
Heads are generally aftermarket, with larger valves, ports, much stiffer springs, and often much higher compression ratio.
Maximum camshaft specs can be in the area of .625 to .725 lift, 250* intake, 270* exhaust, @ .050” lift. LSA runs between 111* and 108*, with very aggressive acceleration ramps.
Spring requirements are in the area of 500lbs to 800lbs open pressure, or more.
Rocker ratio is 1.7 to 1.9
RPM operating range, 3,500 to 8,000 rpm.
This type of build can only live a comfortable life if the very best of everything is used. This includes the top of the line shaft mount rocker systems, designed to accommodate very high spring pressures and extreme camshaft acceleration ramps. Most quality rocker arm manufacturers offer various rocker systems designed to accommodate specific requirements. It is imperative that customers inquire as to which rocker system would best meet their own particular requirements.  

Generally quality aftermarket street rockers have an acceptable maximum spring pressure limit of 250 lbs to 300 lbs open pressure. If this pressure is exceeded, especially with some of the more radical acceleration ramps cam suppliers are providing, using a “street” rocker is a big mistake. While many “street” rockers are of the stud mount variety, some manufacturers provide the much stronger, more stable, shaft mount style. A shaft mount rocker system can often bridge the gap between a highly modified street engine and a race engine. When approaching the maximum limits for a stud mount rocker, simply stepping up to a “street - race” style shaft system can provide much more protection. Most “street - race” style shaft mount rockers should be able to withstand pressures in the 400 plus lb area. Basically, whenever possible, a shaft mount rocker system should always be the logical choice. While there are some very good quality stud mount rockers in the market place, shaft mounted rockers are far and away the stronger system. No stud mount rocker arm can match the strength, rigidity, stiffness, or ability to take the rigorous punishment that a good quality shaft mount rocker arm can. When utilizing higher spring pressures and / or more aggressive cam lobe profiles (so popular today), a shaft mount rocker arm should be the only choice. There are different grades of rocker arms available for shaft mount rocker systems as well. This allows the installer to pick and choose the best rocker arm for his application. A light weight shaft mount rocker arm can be used in stock to moderate, street -race application upgrades, or with lesser aggressive cam profiles that require less spring pressure. Likewise, a stronger, stiffer, beefier, shaft mount rocker arm should be used when higher spring pressures and or extreme rapid lift cam profiles are used in all race - only engine applications. Manufacturers generally indicate the purpose of the rockers as far as suitable loads are concerned. But, purchasing any performance product for one’s vehicle demands the owner do some research. Always ensure your application does not exceed the manufacturer’s maximum recommended spring pressure limit.
When considering a rocker arm system for a “race - only” engine, many of the same kinds of questions relative to a “street - race” engine must be answered. For the most part, if an engine build falls into the above indicated “race - only” engine category, high quality race rockers are demanded. “Race” rockers are generally larger, and stronger than “street - race” rockers to stand up to the rigors of a “race - only” engine application. Race rockers generally have larger, stronger mounting bolts to keep them secure to the head. The highest quality race rocker kits are made from high quality billet Aluminum like 2024T6. This alloy can withstand incredibly aggressive cam profiles and very high spring pressures. 2024T6 actually becomes stronger as the temperature rises. Steel is often used in the most expensive rocker arm kits, but it too can be subject to failure. When a steel rocker arm breaks, it is usually in the area of the trunions or trunion bearings. An oil pan full of needle bearings is a bad thing. While Aluminum is not as strong as steel, it has some flexibility which allows the rocker body to take much of the punishment rather than the trunion.
Extreme camshaft ramp speeds cause the lifter to have difficulty maintaining contact with the camshaft lobe. This condition is often referred to as "valve float". Aggressive or poor cam lobe designs or opening ramps with high acceleration rates can literally hammer the rocker arms and other parts of the valvetrain. To help control this condition, engine builders usually move up to stiffer valve springs. While this tends to solve the immediate problem, other issues generally appear. Exceeding the manufacturer’s recommended / allowable spring pressure limit is a sure way to kill the rocker arms. When in doubt, step up to the next level rocker arm. Doing the job twice is always painful. Determining which rocker to use for your particular application is the responsibility of the engine builder.
High pressure valve springs cause severe loads on the pushrods. These loads imparted into the pushrod cause it to bend and then return to a straight configuration. This unloads a sharp energy pulse to the rocker arm, which transfers it into the valve/valve spring assembly. Continued abuse can cause the rocker arm to fail. When utilizing high pressure valve springs combined with high quality aftermarket rockers, one should also utilize lighter valves, lifters, retainers, and lighter / stiffer pushrods. The end result is more horsepower and greater engine longevity.
Some manufacturers are utilizing a Spintron a highly sophisticated, extremely expensive piece of equipment to simulate incredible loads and real life racing conditions to monitor their product’s durability. The laser feature of the Spintron can plot the actual failures that occur during the tests.
In closing, to insure your rocker arms system will stand up to the rigors of your particular engine modifications, following the guidelines indicated in this article can allow you the comfort of knowing the correct system was chosen. Again, as I have indicated in every article, when in doubt, speak with you engine builder.
 

Article 23 in the Yella Terra “Rocker Arms 101” Series

Adjustable Vs. Non Adjustable – What Rocker and Lifter Combinations Should I Use?

Both stud mount and shaft mount rockers are manufactured in adjustable and non adjustable configuration. There appears to be but one name given to the “adjustable rocker arm”. The name defines the product, “a rocker arm that is adjustable or demands an adjustment to complete the installation”. On the other hand, there are many names given to “non adjustable rocker arms”, bolt-on, drop-in, ”easy-fit”. All these names indicate a non adjustable rocker arm that simply replaces a stock rocker arm with no further adjustment necessary.  The installation of non-adjustable rockers can be as simple as removing the factory rockers and replacing them with retro fitted aftermarket rockers that bolt down with the same hardware that secured the original rockers. Non adjustable rocker arms were designed to be used with hydraulic lifter cams and lifters only.

In either case, ensure that your rocker arm choice is strong enough to endure the valve spring pressure and cam lobe profile you intend to use. More aggressive lobe profiles demand stiffer springs, which in turn demand stronger rocker arm setups. Solid roller cams and lifters also require stronger spring pressures and therefore, much stronger rocker arms. When in doubt consult your engine builder or the rocker arm manufacturer for accurate information.

Article 24 in the Yella Terra “Rocker Arms 101” Series

“INNOCENT UNTIL PROVEN GUILTY”
HI-RPM POWER FAILURES ATTRIBUTED TO ROLLER ROCKERS

For an inordinate amount of time now, I have read forum posts that indicate the installation of aftermarket roller rocker arms caused a valve train problem at high RPM conditions. Often after the installation of aggressive camshafts the same phenomenon occurred. Novices often falsely accuse a modification or recently installed product of being the culprit, when in fact, a lack of experience in the engine building field is the real culprit. Dyno testing by a qualified tuner, with a quality wide band oxygen sensor and run recording capability can quickly locate the problem.
It is also very important that the tuner keep an open mind while testing. It’s real easy to take the easy way out and blame the apparent modification.

On several occasions, after the installation of various performance enhancing products, even though the power and torque were increased at the low and middle of the run, our tuners experienced high rpm Dyno fluctuations and apparent high rpm power losses on our Dynos. Instead of blaming the performance products, we applied basic scientific study and simple common sense. With the proper testing equipment and careful analysis, we often found that the fuel injection systems were not up to supplying enough fuel to provide the horsepower the engines were now capable of making. Remember, Dynos generally test the vehicle in direct drive or high gear. This can deplete the fuel supply much quicker than an on road blast where the vehicle is run through all four gears. Also more horsepower requires more fuel. It’s as simple as that.

The first thing to ascertain is that the fuel pump and lines are capable of supplying enough fuel to injectors. Often stepping up to a high quality fuel pump is a simple and painless answer to high rpm performance loss. Once this is accomplished, the injectors themselves need to be examined.

Keeping in mind the “old rule of thumb” that it takes 0.5 lbs of gasoline per hour to make 1 HP (this is referred to as the Brake Specific Fuel Consumption-BSFC); a 600HP engine will require approximately 300# of gasoline per hour.  Fuel injectors are rated at a certain # of fuel/ hr (ex. 48#/hr), but this is a free flow rating at a specific fuel pressure.  If the pressure is higher, flow will be higher and if fuel pressure is lower, fuel flow will be lower.  Also, in operation, a fuel injector must be turned off at least 10% of its operating cycle (duty cycle).  That means that a given injector of say 48#/hr flow rating will only flow about 43# of fuel per hour (because 10% of its free flow capacity is lost during the “off” time of the duty cycle).   

If we want to make 600HP and we have 8 injectors with a 48#/hr flow rating (43#/hr at 90% duty cycle), we have the injector capacity of 344# of fuel/hr (8 x 43#/hr).  This gives us the capacity to make approximately 688HP if our tuning is in the ballpark.  To be on the safe side, we recommend fuel injectors that would provide the necessary fuel flow at 80% of their free flow rating.  For example; if we want to safely make 600HP, and our BSFC is .500; then we need 300# of fuel out of 8 injectors (37.5#/hr at free flow).  If the injectors are to operate at no more than 80% duty cycle, we need to have 47-48# injectors (37.5 #/hr / 80% = 47#/hr).  If your tuning is good and BSFC is less than .500, then you can have slightly smaller injectors (although you probably would want the safety of the larger injectors).  If your BSFC exceeds .500, you will need higher flow injectors. 

In closing, all too often, we assume the last product installation completed is to blame for a failure that really is due to our own ignorance. When in doubt, consult a professional installation center, before publicly bashing a product that has the potential of taking your ride to a new level.

ASSORTED BITS OF INFORMATION

Tech Tips

So who is right and who is wrong here?  At VHP, we are only claiming to comply with the SAE J604 standard.  That way, VHP can be evaluated with other cams that comply with the accepted world standard.

How To Compare Duration Specs Between Pushrod Cams and OHC!

 Keep in mind that this is an approximation for comparison. OHC cams are much more complex in design than traditional pushrod cams.  This is especially true of cams with finger followers because the effective rocker ratio is constantly changing as the cam rotates through its opening and closing cycle.  Different diameters of bucket followers also have an effect on cam design and performance. For this an other reasons a cam that works well in a Mod Ford, for instance, will not work well in an LSX engine. Also, reverse duration specs can create havoc when used in the wrong application. We have these types of grinds available for very specialized applications.

       Rocker Arm Geometry  -  If you’re looking for the most out of your valvetrain, you’ll need to look at your rocker arm geometry (Stud Mount Rockers).  To fine tune your valvetrain, you are looking for a pushrod length that leaves the roller tip of the rocker towards the intake side of the valve tip, NOT dead center of the valve, when the valve is closed.  You will see that the pushrod side of the rocker probably will have to drop down, and the roller tip will then pull back toward the intake side.  This will be achieved with shorter length pushrods and will help you get better power because you will be opening the valve quicker.  This will also leave the highest spring pressure load occurring with the rocker tip at the center of the valve at full lift, not off towards the exhaust side.  Just be careful not to get into contact with the top of the retainer and the underside of the rocker arms when setting up this geometry.

    Lofting:  is a term used to explain a lifter leaving the surface of the cam lobe and thrown over the nose of the cam.  This will happen at higher engine speeds after the valve train is accelerated up the opening side of the lobe and in a period of rebound.  The rebound period occurs on the opening side of the lobe when the lifter is still on the rise portion of the lift curve and extends beyond the nose of the cam.  When the inertia load becomes greater than the open load provided by the valve spring, separation will occur over the nose and extend down the closing side of the lobe.  If a smooth and controlled connection to the closing side of the lobe no longer occurs due to increasing engine speed, the potential for valve train damage dramatically increases.  Lofting can be minimized by the use of rigid, low mass valve train components, such as hollow stem valves, titanium components, and short large diameter pushrods. Limiting engine speed during wheel spin and missed shifts will also minimize the chance of valve train damage.

Ignition Timing vs. Valve Timing

Frequently, our phone techs get inquiries from our customers about what ignition timing to run with a given camshaft.  Sometimes, they ask about how ignition timing relates to valve timing (cam timing).  The answers to these questions are difficult because there is really no way to answer their questions with the limited amount of information provided. 

Determining proper ignition timing at idle and under all part throttle and WOT conditions is extremely complex and should be handled by an experienced "tuner."  It is not unusual to require several "tuning adjustments" before a timing "curve" is "dialed in."  This is a situation where patience and perseverance can pay huge dividends in performance and dependability.

You may have noticed that most VHP cams have a certain amount of advance ground into them when you check out the camshaft specification card.  This is primarily done to insure that you have adequate torque to establish a good performance baseline.  We have also found over the years that the correct camshaft for most applications will run best with some amount of advance in it.  We believe that it's certainly better to begin with too much bottom end and mid-range torque, and tune from there, than to have a shortage of torque, and try to figure out how to compensate for that.

 ROCKER RATIO

 < CLICK HERE FOR MORE INFO > 

DOES HEIGHT REALLY MATTER?
 
When it comes to valve spring installed height, it really does matter. Installed height is the dimension measured from the bottom of the outer edge of the valve spring retainer where the outer valve spring locates, to the spring pocket in the cylinder head, when the valve is closed.
 
Why is this important?  The installed spring height is the determining factor of what the valve spring "seat pressure" and "open pressure" will be. Both our camshaft specification charts and the spring section of our catalog show what the spring pressure will be at a particular installed height. Spring tension may vary even within a production run, so we always recommend that each spring be tested on an accurate spring tester prior to final assembly.  Spring seat pressure can be adjusted to equalize tension or pressure, so check our web site or our catalog for tips on changing installed height.
 
Keep in mind you always need to run enough seat pressure to control the valve action as it returns to the seat.  Obviously heavier valves require more seat pressure.  Lighter valves require less seat pressure.  If you are not sure, it is better to run slightly more seat pressure, not less. According to the extensive testing we have done, heavier valve spring pressures do not rob horsepower.  For every spring that is using energy to become compressed there is an opposing valve that is already compressed and full of energy, that offsets the energy being used to compress the opposing spring.  Better control of the valves usually means significantly improved
power at top end

·         Let The Air Out  -  The Generation IV big block Chevy needs to have the front lifter oil gallery plugs modified by removing them and drilling a .030” hole in the center of the plug and then re-installing them. This hole will bleed off any air locked in the front of the galley oil passages. This air lock can cause the front lifters on both sides of the block to starve the oil supply up to the rocker arms, plus starving the lifters causing them to clatter.

ALERT!

IT HAS BEEN BROUGHT TO OUR ATTENTION, THAT SOME INSTALLERS HAVE FAILED TO PROPERLY TIGHTEN THE BOLTS ON THE ROLLER TIMING SETS. THIS IS A GUARANTEED FAILURE. PROPER TORQUING OF THESE AND ALL FASTENERS ASSOCIATED WITH ANY INSTALLATION IS THE RESPONSIBILITY OF THE INSTALLER. THE BOLTS WILL BACK OUT AND INTERACT WITH THE TIMING CHAIN WHICH CAUSES THE CHAIN TO BREAK. SERIOUS VALVE DAMAGE CAN OCCUR. THE INSTRUCTIONS CLEARLY STATE TO TORQUE THESE BOLTS TO 10 FT LBS. "WORD OF ADVICE!" ASK YOUR INSTALLER TO CHECK THE TORQUE ON ALL FASTENERS.

GET IN LINE

To confirm proper alignment, install the crank sprocket (apply mild heat via submersing in hot water if necessary to ease installation), making certain that it is up against the register on the crank. Then install the upper sprocket onto the camshaft, including any thrust bearings, thrust shims, retaining plates, etc. Then install the camshaft (without timing chain) into the engine, torquing all fasteners as required. You may also want to install the front balancer at this time, to insure that the crank sprocket is being properly positioned. Place a straightedge against the front edge of the sprockets, and inspect to confirm that straightedge contact is continuous on the sprockets. If the cam sprocket is too far back, a thrust shim may be able to be added behind it to obtain proper alignment (you'll need to make sure that the lifters and lobes are still properly aligned if you use this option).  If this is not possible, a step on the rear of the crank sprocket may have to be machined to allow it to slide further back on the crankshaft.  If the cam sprocket is too far forward, the thrust surface on the rear of the cam sprocket may be machined (again check lifter to lobe alignment), the thrust face of the block may have to be machined (yes, engine disassembly time again), or a shim placed behind the crank sprocket to achieve alignment.  
There are numerous possibilities to correct misalignment, depending on the engine type and optional timing components that may be available. The main thing is to check this as early as possible in the engine building process, allowing you the time to exercise different choices to correct any difficulties.  Also, check to be certain you have sufficient clearance between the chain and the block casting, and the chain to the timing cover. With many of today's wider chains, space may be at a premium. Checking these factors will help allow your engine to have a good, long life. This is cheap insurance to protect your investment.    

TRUCK TECH TIP 
*         Do you know when to be "wild" and when not to?  Well if you are driving a truck that is really an important decision.  Why? Because setting up your truck for how you regularly drive it is really the "map" for your set up.  From a daily driver to rock climber, to actual drag racing, your plan for daily use will give you the right recipe for maximum performance.
 
While "race only" trucks will opt for max lift and duration, we recommend that you build for maximum torque for a daily driver.  Trucks are beefy and weighty and maximizing the torque will get it up and going quicker so that your zero to sixty mph elapsed time is quicker even when more heavily loaded or towing.  Be careful in selecting larger carburetion or intake manifolds, high flow fuel injection, or headers, etc.  Remember that max torque comes from maximum airflow velocity not volume!  Our advice is, unless you are an all out racer, keep it "mild" and don't go "wild."  After all, mom will be proud of you!
 
Pushrods: The #1 Cause of Valve Train Problems / Stiffer Pushrods Always The Right Answer!
 

Can Rocker Arm “Weight, Mass, and Moment of Inertia” Lead To Valve Float?

We have noticed a considerable wear pattern on the front of the camshaft retainer plate, on the all of LSX series engines, including  LS1, LS6, LQ4 etc trucks and on the new LS2 engines, as well. We believe this is due to improper oiling, between the plate and the timing gear.  (see picture 1).  This wear occurs with stock cams and after market cams as well, as it is a manufacturing defect not an aftermarket products defect. We have observed this wear on all of the LSX series engines with as little as 500 miles on them. VHP is bringing this information to our readers attention in hopes of preventing a serious engine failure. We have seen a material build up on magnetic oil pan drain plugs which, in some part, is due to the cam plate wear. We highly recommend using the Crane hex-adjust timing set on all cam installs, part number 144984-1.  The bearing at the rear of the cam gear prevents most incidence of wear from re-occurring . (see picture 2).  Here at VHP we have been notching the retainer plates for better oiling, to minimize this problem.  (See picture 3).  Upon tear down of test engines notching the plate and utilizing the Crane timing set has alleviated the problem.
 

·         LS1 Timing Chain And Gear Set

      mSome things are just forgotten or not worried about.  Your valve spring can be one of these forgotten parts.  Whether it’s a new cam install, a new valve job on an old engine, a change in rocker arm ratios, new heads, etc., you should always make sure that your combination works for the part(s) you install.  First of all, find out what is recommended for the part(s) you are installing, then take some measurements like “Installed Height” of the springs you have, “Coil Bind” height and the I.D. and O.D. of the spring seat.  If you insist on using the springs you have, you will still need to know where the springs coil bind and what spring pressure range you should be in so that you will not have “Valve Float” (too little spring pressure in this case) or “Coil Bind” (coils are actually smashing together).  Once you have your installed height and you know your coil bind height, make sure that you have at least .060“ extra cushion before coil bind.  This way you will have enough room for the spring to travel safely without the spring breaking or coming apart from being overworked.  To find this out, you will need to subtract your “Lift at the Valve” and .060” from your installed height.  (Example:  1.700” installed height / coil bind is at 1.100” / .500” lift at the valve leaves you with .100” extra travel before coil bind.  If you have a dual or triple valve spring, you will also need to make sure what the coil bind on the inner spring(s) will be.

Chevy High-Performance Magazine LS1 Project Truck Gains Average 25 HP

Our point is that the only thing that counts is what happens at the valve and the overall rocker ratio is fundamental to this. Contrary to popular belief, there are no fixed ratio rockers on the market (this is because the valve tip end and pushrod seat end operate on two distinctly different arcs). This is why some rockers add power and some don’t. VHP has elected to do extensive development with rockers as a supplement to the lobe. The quickest lobe in the world doesn’t mean diddly if you are using slow acting rockers! Like everything else, it’s the combination that counts. FYI, the higher opening and closing ratios actually allow lower seat pressures because the mechanical advantage of the ratio helps maintain proper lifter preload! Check it out. This isn’t smoke and mirrors; it’s applied geometry and it works!! Roger Vinci

Quiet “ACCELERATED-LIFT’ Roller Rockers Are A Solid 25 HP Increase For LS1 / LS2 / LS6 Engines!

 Many people mistakenly think other engine modifications are more important, but this is false thinking.  The camshaft is the “gatemaster” to the flow into and out of the cylinder, but this and all of the other engine components must be matched to putting the power in the RPM range that the drivetrain can use.  Once the camshaft is selected, modifications to components on both the intake and exhaust must complement the system.  It is no good to have a high flow intake system (large throttle body, high-flow intake manifold and custom cylinder heads) if the exhaust can’t get rid of the combustion products.  Proper cam selection takes years of real world experience, which often resulted in as many failures as successes.  Let’s face it, you often learn more from your failures than your successes.  At VHP, the people on hand to answer your technical questions have combined experience in the performance aftermarket of over 100 years!  Call us with your questions; someone around here either knows the answer or knows where to get it!

Quality Steps. . . Or How Lobe-to-Lobe Accuracy Affects HP And Durability!

A Matter of Degreeing-in, And Of Lifters!  When degreeing a camshaft, be sure to use the same type of lifter that the camshaft is designed for.  You cannot properly degree a flat tappet camshaft by using a roller lifter, and neither can you degree a roller tappet camshaft by using a flat faced lifter.  This error does occur with some frequency, so be sure that you ask this question if a customer has trouble when checking their VHP camshaft.

Cams For Stroker Motors  -  Don’t forget that when you go to a larger cubic inch that the motor is going to have its RPM range shifted downward because of the cubic inch increase.  So to get the same RPM range you had, you should increase both cam lift and duration.  If you need increased torque, stick with the cam you ran previously to get the benefit of the increased low-end torque.  Of course, if you  need to discuss any of these problems or are “just plan lost” trying to choose the right cam profile, call us at (407) 478-VETT.  We’d be happy to help you select the cam that’s best.

 Pushrods  -  If you’re looking for more power and the full lift of the cam that you have, you  must realize that your pushrods will flex under heavy loads (spring pressure, cam profiles, etc.) and RPM.  This can and will happen on any style cam from a relatively mild hydraulic flat tappet to a mechanical roller.  When pushrods flex you lose valve lift… and horsepower!  To reduce this lift-robbing flex, we recommend that you use the heaviest pushrod wall you can find (.060” - .080” is the norm to buy).  The wall thickness will help stiffen the pushrods and keep the pushrod flex to a minimum.  This allows the valve to get the full lift of the cam without as much flex.  We offer one-piece pushrods in .050” length increments with .080” walls in 5/16” from 6” – 8.950” in length and 8.200” – 11” in 3/8” diameter.

 

CLUTCH SHIELD INSTALLATION INFORMATION TIPS
Undo the bottom of both front shocks. Loosen the four cross member bolts. Drop the rear of the motor as far as possible. Remove the bell-housing. Install the clutch shield and bell-housing at the same time. Allen head bolts help ease the installation. They are available at most hardware stores.