It’s often said that necessity is the mother of invention. In a high-performance engine, some stock components are stressed beyond their intended capacity. That can result in individual component failure, which can then result in complete engine failure. To prevent such issues, improved replacements are oftentimes available on the aftermarket, but once in a while a weak link surfaces, and that’s when a mind like Scott Sims’ gets working.
Scott owns Sims Performance Machining (SPM) in Elizabethtown, Indiana, and his circle-track racecar is powered by a healthy Pontiac V-8. He applies and releases the throttle countless times throughout the course of a race, and that action thrusts the camshaft fore and aft. “The helical cut of the distributor gear forces the cam toward the front of the block at full throttle, and toward the rear of the block while decelerating,” says Scott.
The constant thrust is very hard on the stock Pontiac camshaft retainer, and over time it can flex or break, taking the engine with it. As the cam floats against the retainer, spark timing can walk around too. Scott laid eyes on a piece that a racer buddy was using in his Ford. “It was a modified timing set that used roller bearings to control camshaft endplay. It improved timing steadiness and reliability, while reducing parasitic drag. I decided to make one for my Pontiac, and it worked so well for me that I began offering it to others.”
 This might look like an...
 This might look like an ordinary Pontiac V-8 timing set, but it’s a precision assembly from Sims Performance Machining (SPM) that features high-quality components and roller bearings to improve reliability and timing steadiness, and reduce parasitic drag.
SPM constructs a new camshaft retainer plate of 01 tool steel, a material much more durable than the stamped steel Pontiac originally used. It’s machined to accept hardened races for the flat Torrington roller bearings, which reduce friction and limit endplay to 0.005-0.007 inch. While a jet of pressurized oil lubricates the timing chain with the stock Pontiac retainer, the SPM piece is further modified to positively oil both roller bearings also. “We did it in such a way that no modifications to the block are necessary,” adds Sims.
The cam gear must be modified to accept the roller bearing and Sims specs a Rollmaster set for its billet steel gears and durable roller chain. “The integrity of the billet gear isn’t compromised during machining,” says Sims. “A cast-iron cam gear may be machined similarly, but I don’t feel it’d be strong enough after machining for such an application.”
With the Roller Bearing Camshaft Retainer installed onto a test engine, Sims found spark timing extremely steady, indicating that the cam wasn’t walking in either direction. “We tracked it on the dyno and found timing was rock solid at all speeds.” That steadiness and the friction reduction provided a gain of 9 hp and 10 lb-ft in a back-to-back test on what Sims refers to as “a typical street 455.” He adds, “Though customers have reported positive results in many instances, power gains may vary with the application.”
 The key to the assembly...
 The key to the assembly is the custom-made camshaft retainer. Machined from tool steel, it’s much more durable than the stock piece and is machined to accept flat Torrington roller bearings.
SPM’s Roller Bearing Camshaft Retainer kit is available with a standard length timing chain, or in variants measuring 0.005 and 0.010-inches shorter for instances when the block has been line-honed or bored. A complete kit retails for $265 and is available directly from SPM. Those hobbyists already using a Rollmaster timing set in their Pontiac can opt to ship it to SPM for machining and save $100 on the cost of the kit.