Belt Drives


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How often should I change my belt?

For V8 drag race applications, it is recommended to change 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, it is highly recommended to replace 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, it is recommended to run 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. Jesel has 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 the Jesel 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?

Jesel tries to make their 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. It is highly recommended to test fit 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. There are too many discrepancies in the placement of dowel pins and keyways in aftermarket camshafts and crankshafts.

How do I adjust cam timing?

For the 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 the 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.


Multi Motorsports, LLC