One area of our hobby that seems to generate heated debate is camshaft selection. The recurring arguments typically involve a favorite brand or specific valve timing, but lately, oil-quality-related issues (see "The Slippery Truth About Oil," June '06 HPP) and roller technology have been tossed into the mix. Add to this that not all points are supported factually but more so by opinion, and you can literally watch disaster unfold before your eyes.
So where can hobbyists turn when searching for unbiased answers about camshafts on the market today? We contacted a group of respected engine-building experts about this very topic, and here's what they had to say.
A History Lesson
Q. Can you provide some developmental history about Pontiac's original camshafts, the production concerns, and how specific grinds were selected for an application?
A. Even the most passive Pontiac hobbyist should immediately recognize the name Malcolm R. McKellar. McKellar is a retired Pontiac engineer who, in his 40-plus years with the division, was directly associated with the development of the Pontiac V-8, the original Super-Duty program, and a number of cutting-edge camshafts. Wanting an insider's view about camshaft design during Pontiac's glory days, we contacted McKellar and asked for his comments.
"I wish we could have used roller technology back then. It would have cut friction and allowed us to improve performance and street manners, but it wasn't available at that time," says McKellar. "We used hydraulic camshafts in nearly every application, but chose mechanical cams for the Super-Duty engines because solid lifters better follow the ramp profile for maximum performance and eliminate the pump up that can reduce high-rpm power."
When designing a camshaft and deciding on maximum lift, McKellar says, "Increasing rocker-arm ratio can actually give you more flexibility, but excessive ratios can be hard on the valvetrain. By installing higher-ratio rocker arms, you increase everything under the lift curve and can make the camshaft appear slightly larger at the same time. Either form was acceptable with the lift ranges and ratios that we worked in."
McKellar says the division limited gross valve lift to just over 0.400 inch in most instances simply because it was less stressful on the valvetrain. "Our heads had good port velocity and larger valves, so we didn't always see the need to increase valve lift and press our luck on durability. You have to remember, too, that not all of our engines went into performance applications. But we did have a few high-lift camshafts like the Nos. 7, 10, and 041."
During the late-'50s and early-'60s, Pontiac produced a small line of performance camshafts, such as the Nos. 7 and 10 that bear McKellar's name. According to McKellar, these were developed to compete with the high-performance Pontiac camshafts offered by outside camshaft manufacturers. "Their cams were rather generic where ours were designed for specific applications. My name was added to simply give them a unique marketing identity."
Many of the division's most popular camshafts were developed during the mid-'60s. The Nos. 066 and 067 were considered the workhorses, offering the best performance compromises, while No. 068 was used in high-output applications. "We kept hearing from Jim Wangers that our engines ran out of rpm before crossing the finish line on the dragstrip," says McKellar. "So we stepped up duration and developed the No. 744 to increase the top end of our Ram Air engines."
McKellar states that when selecting a camshaft for a specific application, the engineers often let the combination tell them what it wanted. "In the early years, we installed different camshafts and then road-tested the vehicles to find the best grind for each application. We found that manual-transmission engines could tolerate a little more duration, and buyers usually wanted to spin them a little higher, so a lot of times, they got a bigger cam. Most of this went away when emissions became more of a concern."
The No. 041 was often touted in vintage sales literature as the division's first "computer-designed" camshaft. Of that, McKellar says, "That's somewhat true-but not totally. We used a computer to generate the blueprints, and computer technology was hot at that time, so advertising decided to incorporate that. The No. 041 was a great performer, but I feel the No. 10 was a little better. Its solid lifters allowed for more low-end and midrange power than the hydraulic 041."