Top 6 Cam Questions Answered - Pontiac Tech

The Bread-And-Butter Hydraulic
Q. Has recent lobe-profile technology had any effect on today's hydraulic flat-tappet camshafts, and what limitations do such cams offer?

A. Hydraulic flat-tappet camshafts have been around for decades. The concept entails lifters that continually adjust by bleeding off a specific amount of pressurized oil to maintain minimal valve lash and ensure quiet operation. Though bleed rates can vary from lifter type and manufacturer, the rate remains constant regardless of oil pressure or engine speed. As engine speed increases, however, some standard lifters are unable to bleed oil quick enough to fully seat the valves at high rpm, leading to a condition commonly referred to as "pump up."

A number of general camshaft advancements applied to hydraulic flat-tappets and its lifters have narrowed the performance margin and increased their value in street applications. Jeff Kauffman of Kauffman Racing Equipment in Glenmont, Ohio, tells HPP, "Hydraulic flat-tappet cams are basic technology and will probably be around for a long time. We still sell lots of them. They are low-maintenance and easy on valvesprings, but the number-one factor for their popularity is pricing. Not everyone has the additional $800 or so budgeted for a roller-cam upgrade."

Speaking specifically of the latest technology used by camshaft manufacturers, Kauffman says, "Today's cams have quicker ramps and smaller base circles, which typically lift the valve off its seat quicker, but actually delay the initial opening point. This limits valve overlap and keeps cylinder pressure high. We're finding that we can make big numbers with them, but it seems that hobbyists start stepping up to a solid flat-tappet or hydraulic-roller around the 500hp mark."

Kauffman feels the only negatives associated with hydraulic flat-tappet camshafts are the slight power loss when compared to solid flat-tappets or hydraulic-rollers and potential lobe-failure issues. Of the latter, he says, "We practice good installation and break-in procedures and have never had one fail on us. They are a direct bolt-in for an original and are a relatively cheap horsepower upgrade for many street applications. They're simply the best bang for your performance buck."

Stepping Up Solidly
Q. What typical advantages does a mechanical flat-tappet camshaft have over a hydraulic, and how do you address the recurring hobbyist concerns?

A. Anyone on the performance scene during the '60s can tell you that in those days a mechanical camshaft offered a clear performance advantage over a hydraulic. The audible solid-lifter symphony was a distinct indication that an owner was serious about performance, but the low-tech rocker-arm locknuts used back then sometimes required adjusting to maintain valve lash. Though the situation was oftentimes exaggerated, the mechanical cams were ultimately hung with the reputation of high-maintenance, noisy units. Only now with modern high-tech positive-locking rocker nuts are mechanical cams shedding that image.

Jim Taylor of Jim Taylor Engine Service in Phillipsburg, New Jersey, has been building and racing Pontiacs since the mid-'60s and has used mechanical camshafts in myriad performance engines. "In street/strip applications, they offer enhanced power at all points over an identical hydraulic grind and produce more manifold vacuum at idle," he says. "The solid cam opens the valve quicker and holds it open longer at the higher lift range, allowing for a larger cylinder charge. It's of more interest when degreeing a solid cam to read duration at 0.200-inch lifter rise than at the SAE standard of 0.050-inch used with hydraulics and low-lift solids."

"When having to reduce compression for today's fuel octane in street engines, old solid grinds were not compatible because they were designed for high-compression engines," says Taylor. "When developing my own TFX grinds in the early '90s, the designs came from a lot of street and dyno testing. I use Crane for custom solid and roller grinds, but Crane and Crower both offer excellent catalog cams, which we use routinely."