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ROCKERS

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What do you look for when setting roller geometry and sweep pattern?
We set our aluminum systems with a low pivot geometry which results in the majority of the sweep pattern occurring while spring pressures are at their lower range. The majority of roller travel occurs from zero lash to half lift which results in minimum roller travel for the duration of lift when spring pressures are greatest. At zero lash, the roller should start approximately .050” behind the center of the valve stem, sweep across center and end near the center at full lift.

What is the proper way to set valve lash?

Starting at #1 cylinder, rotate the engine until the #1 exhaust rocker just starts to open the exhaust valve. Set the valve lash on #1 intake rocker at this time. Continue rotating the assembly and stop when #1 intake rocker starts returning from full lift. The lash on #1 exhaust can now be set. Continue this procedure for the remaining cylinders following the engines firing order.

Do I have to torque the adjuster nuts?

We highly recommend using a torque wrench when setting valve lash. Our recommended torque setting for a typical 3/8-24 cup or ball style adjuster is 25 Lbs-Ft. Over tightening the adjuster nut stresses the thread area in the rocker body leading to premature rocker arm failure.

Are there any break-in procedures I need to follow?

The most critical step in initial start-up is the proper break-in of the adjuster cup to pushrod tip surfaces. We supply a high pressure lube with all rocker kits to prevent premature failure and wear of the adjuster cup area. The shaft bearings are fully lubricated from Jesel and only require splash lubrication once running.

My adjuster is screwed fully into the body and I still can’t get lash. Can I drill out the body and sink the adjuster?

NO! We see more rocker failures due to this procedure. Invest in shorter pushrods or if it’s an emergency, raise the stand slightly. NEVER modify the adjuster cup counter-bore area.

How far out can I run my adjuster?

We recommend not running the adjuster turned out more than two revolutions from the fully seated position. All rockers are shipped from Jesel with the adjuster set at one full turn from seated. Operating an engine with the adjusters more than two turns out puts excessive loads on the cup area and may lead to premature failure of the adjuster.

When should I be running needle bearing nose rollers?

We highly recommend needle nose rollers on any application using 5/16” diameter or smaller valve stems. Open spring pressures and valve lifts are also factors to look at when ordering a rocker system. We have what we call our 800-800 rule. Any application running more than 800 lbs open or over .800” worth of total valve lift should be running needle nose rollers.

My rockers are rubbing the retainers. Can I relieve the area for extra clearance?

Yes, it is safe to remove a small amount of material from the underside of the rocker to gain additional clearance between the body and retainer. We recommend using a ball type end mill and not something like a “fly-cutter” which will leave sharp edges. Stress fractures can occur if sharp edges are left after machining so be sure to round all sharp edges. We can provide this option when rockers are being manufactured.

When should I replace my rocker arms?

There is no set time to replace a rocker arm body and generally there are many factors involved such as spring pressures, operating temperatures and the occasional over-rev. Aluminum bodied rockers will fatigue over time and varies by application and operating environments. One of the first signs of fatigue is the failure of the body surrounding the adjuster.



ROCKER GEOMETRY

Rocker geometry is a function of the arc generated from the rocker arm and the relationship of the valve tip to rocker shaft height. Using this arc correctly is the difference between a smooth operating valvetrain and a valvetrain of worn out parts. Jesel’s Low Pivot geometry utlizes the portion of the arc that produces a minimal sweep pattern from half to full lift, a point at which spring pressures are exponentionally increasing. These added spring forces transferred against the nose roller have the potential to cause the roller to skid instead of roll across the tip bending the valve stem and wearing the guides. By minimizing the roller travel distance under high spring loads, the potential of roller skidding is reduced and valve guide wear decreased tremendously. As illustrated below, the Jesel Low Pivot geometry yielded almost .020” less roller travel during the critical stages of lift compared to a rocker set up for a symmetrical half-lift geometry.



BELT DRIVES

How often should I change my belt?

For V8 drag race applications, we recommend changing the belt after about 250 passes. For any type of oval track or endurance applications, the belt should be changed when the engine gets freshened. If you experience any engine failure that may have even temporarily locked up the rotating assembly, change the belt, its cheap insurance.

Is it OK to clean the belt?

The belt can be cleaned with mild soap and water detergents. Never use harsh chemicals such as lacquer thinner, brake clean or mineral spirits. If the belt gets saturated with engine oil, we recommend replacing it.

Should I cover my belt drive?

If you are running your engine on an abrasive surface such as a dirt track, it is highly recommended to shield the front of the drive to keep dirt and debris from damaging the belt and pulley surfaces.

How much camshaft endplay is acceptable?

On belt drives with adjustable thrust plates, we recommend running approximately .010” camshaft endplay. Excessive amounts of endplay can cause premature lifter failure while not enough will limit the amount of oil reaching the thrust surfaces. We have cam adapters available for certain models which utilize a needle bearing thrust assembly instead of bronze thrust washers. The needle bearing assemblies can be run down to as little as .001” worth of camshaft endplay.

How much belt backlash is acceptable?

Due to the round tooth profile inherent with the Gates HTD® timing belt, belt backlash between 2° and 4° degrees is acceptable and normal under a fully assembled valvetrain. If you experience backlash greater than 4°, it may be necessary to use an undersized belt or oversized upper pulley. Jesel stocks undersized and oversized belts for all applications.

Should I oil the crank seal before installing the lower pulley?

The seals used in our belt drives are Teflon® coated and should be installed dry for proper break-in. You should not oil the seal area on the lower pulley or the cam adapter.

Will my cover fit without modifying the block?

We try to make our belt drive covers as universal as possible and have it bolt on to several applications, but due to the vast number of aftermarket blocks that are modified from OEM prints, it may be necessary to machine the block for additional clearance. We highly recommend test fitting the components before any final assembly work is completed.

MY block has been aligned bored. Can I still use a belt drive?

The belt drive cover plate locates off the OEM dowel pins and is set to the factory cam to crank centers. The material used in the seals can adapt to a cam to crank center that varies by as much as ±.015”. If your block has been aligned bored more than .015”, you will need to remove the dowel pins and allow the cover to center itself off the installed lower pulley and cam adapter.

Will I have to use a degree wheel to set cam timing?

It is highly recommended to degree in the cam using a high quality degree wheel. The alignment dots on the upper and lower pulley are for general reference only. We have seen too many discrepancies in the placement of dowel pins and keyways in aftermarket camshafts and crankshafts.

How do I adjust cam timing?

For our 2 piece cam drives, loosen the four upper pulley nuts and rotate the crankshaft clockwise to retard or counter-clockwise to advance the cam timing. To adjust the timing on our solid upper pulley drives, you will need to remove the upper pulley and rotate it to the appropriate degree mark. Always check to see that the engine has adequate piston to valve clearance before altering cam timing.



LIFTERS

What type of oil should I use?

We recommend soaking the lifters in mineral based oil prior to installation as well as pre-lubing the engine prior to startup. After initial engine break-in, if you are going to use synthetic based oil, we highly recommend oils containing high zinc content formulated for racing applications. Synthetic oils formulated for street use are not recommended due to a lack of zinc content.

Do your lifters have a pressurized oiling circuit?

Yes, all of the lifters we manufacture since 1995 have an internal oiling circuit that feeds pressurized oil to the needle bearings in the roller insuring constant lubrication and elimination of any contaminants. There is also a feed hole that sprays oil to the outside diameter of the roller to help prevent cam lobe wear.

Should I be running oil restrictors?

No. Let the lifters be the restrictors. With the spring pressures and ratios being used in today’s racing engines, the lifters need as much oil to them as they can possibly get. Whenever possible, we suggest plumbing the block so that oil is fed equally to the lifters through the front and rear of the oil galley. In the event that you are getting excessive oil to the top end, provisions should be made for better oil drain back to the pan; either by external scavenging lines or internal drains.

How much lifter-to-bore clearance should I be running?

For a cast iron or bronze bushed blocks, we recommend running +.002” clearance cold. If you are running your lifters in an aluminum block without bushings, we recommend running +.0012” clearance cold and preheating the block prior to startup.

What is the advantage to using a larger diameter roller?

The larger the diameter, the stronger the roller. This is due to an increased cross sectional area between the I.D. and the O.D. of the roller. Also, a larger diameter roller rotates slower and reduces the loads needed to open the valvetrain. You may have to adjust your cam specs when using a larger diameter roller due to an increase in duration. A larger diameter roller may allow you to get more aggressive with your opening ramp design.

Why are your lifters so expensive?

The cost is a result of the highest quality materials being produced in small, quality controlled lots held to tolerances as low as .0001” of an inch. All components, with the exception of the needle bearings, are manufactured in our Lakewood, NJ facility on dedicated CNC machining centers and processed using the latest aerospace coatings and heat-treating procedures.

Why are your pushrod seats so low?

The closer the pushrod pivot point is to the bottom of the roller, the less leverage there is for the body to “rock” in the lifter bore. Think of it this way, if you’re trying to tip something over, the higher you push, the easier it gets.

I don’t see a snap ring holding in the axle. How is the axle held in?

All Jesel lifters feature an internal locking pin that secures the axle to the body. With our design, external snap rings and spirolocs that occasionally come loose causing severe engine damage is eliminated.

When should I replace my lifters?

Unfortunately there is no set time. There are many factors to consider such as operating environment, oil used and valvetrain stability. With proper care and maintenance, it is not uncommon for a lifter in a circle track application to see 2000 miles and a drag car with hundreds of passes down the strip. Jesel can inspect your lifters and provide you feedback on the expected life.

Can my lifters be rebuilt?

Most lifters purchased after June 2007 can be fully rebuilt. The procedure takes about a week and is only done here in our Lakewood, NJ facility. Due to design changes, we do not recommend rebuilding lifters purchased prior to June 2007.

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