BELT DRIVE

In the late ‘70s Dan was looking at a belt-driven Chevy Cosworth Vega head, and came up with the idea of adapting this technology to a pushrod V8. That’s where many people would have stopped, but with Dan’s design regime of continuous improvement the end result is a belt drive system that not only drives the camshaft, it facilitates quick cam timing changes and the ability to swap cams through the front cover. It has also led to the elimination of the traditional cam-driven distributor allowing larger engine setbacks and uncompromised intake manifold design. Before the advent of the Jesel belt drive you had to drop the oil pan and remove the timing cover to swap cams or to change cam timing - a time consuming and unpleasant job at the track or shop.

Why Belt Drives

For the race industry, Jesel’s introduction of its pushrod V8 belt drive could not have been timed better. In the early ‘80s NASCAR engine development was outpacing the capacity of the traditional timing chain and sprockets - they just couldn’t finish a 500 mile race. While in the straight line world of drag racing, engine builders were discovering timing chain limitations when working with higher rocker ratios, bigger cams and stiffer springs. The only other option for engine builders were gear drives, known for horsepower soak and durability issues. Slowly NASCAR embraced the new belt drive technology, and for the last 30 years it has been one of the most reliable components in these highly stressed engines. And, in the past several years every NHRA Pro Stock engine was running a Jesel Belt Drive - in fact you would be hard pressed to find a high performance engine in the pits not running a belt drive. Whether you are running 600 miles in a NASCAR race, 1320 feet in a NHRA Pro Stock or a 24hr endurance event, the durability of the Jesel belt drive is legendary. 

The Gates patented High Torq Drive™ reinforced belt spins dry on a steel crank pulley and a hard coated billet aluminum upper pulley. It helps isolate crankshaft vibrations to the valvetrain and the ignition system. Teflon® coated high vacuum cam and crank seals are long lasting and insure the extreme amount of vacuum found in today’s race engines stays sealed in the crankcase. There are two styles of upper pulleys, the original pulley is a two-piece design and enables the cam timing to be infinitely adjusted ±10° while a limited availability solid upper pulley design can be adjusted ±8° in 2° increments. 

The reduction in camshaft endplay is also another huge benefit when using the Jesel belt drive. Minimizing camshaft endplay has a tremendous positive effect on the life of a roller lifter. Keeping the camshaft from thrusting front to rear keeps the lifter rollers from side loading the roller bearings. With the addition of a Jesel Torrington needle bearing cam adapter, camshaft endplay can be limited to as little as .001”. 

The Jesel belt drive has enabled engine development to move forward in other areas as well. The numerous raised-cam aftermarket blocks available today could not exist without some type of belt drive system. Center-to-center pulley distances have grown from 4.520” for the original small-block Chevy to a whopping 7.950” on some aftermarket billet big-blocks. Instead of using off the shelf belts, Jesel has its Patented Gates High Torq Drive™ belts custom made to the exact length required for its belt drives.

Combining Belt & Distributor Drives

Another advance in performance engine development due to the Jesel belt drive is the belt-driven front distributor drive. Why would you want a belt driven front distributor drive? As spring pressures, rocker ratio and rpm have increased, cam torsion and vibration have also increased causing erratic timing. With most common crank triggered ignition systems, the distributor has been relegated to simply connecting the coil to the spark plug. The problem with having the distributor driven off the rear of the cam is that the torsional load on the cam causes an inconsistent ignition signal. Where you set the phasing at idle is not where it is at 9000 rpm. By disconnecting the distributor from the tail-end of the camshaft and driving the distributor’s rotor by a toothed belt from the front belt drive pulley on the camshaft, the distributor is isolated from virtually all cam torsion and vibration providing a true and stable ignition signal.

There are a few other advantages to relocating the distributor drive to the front of the motor. Most importantly the distributor is no longer trying to take up the same real estate as the intake manifold. Manifold runners no longer need to be shrunk or rerouted around a distributor housing. A front-mounted distributor also makes engine setback easier and gives the distributor better access to tune and work on. Plug wire routing is cleaner too, making it easier to check plugs and remove the valve covers. 

As cylinder pressures increase, such as those in nitrous or turbo applications, more voltage is needed to ignite the fuel mixture. The ignition output developed with the new digital ignition boxes increases the potential for cross firing within the cap. Jesel has solved the cross firing issue with its Extreme Series Distributor Drive. This drive features the larger diameter MSD Pro-Cap to prevent cross firing inside of the distributor.

Jesel also has an Individual Cylinder Timing (ICT) system available for both its Pro and Extreme Series Distributor Drives. The ICT system features a magnetically embedded rotor on the back of the distributor that’s used to signal cylinder timing for electronic fuel injection or coil-on-plug ignitions.

It’s hard to believe that something so basic as connecting the camshaft and crank with a belt could change so much, but that is how it is with Dan Jesel. Once he realizes the potential in something, he doesn’t let go until he has wrung every ounce of performance out of it, and racers everywhere are better off because of it.