Camshaft technology is continually changing. From new lobe profiles to various forms of lobe placement, each manufacturer takes its own approach to modern performance. While flat-tappet grinds remain popular for reasons including overall cost and installation simplicity, retrofit roller technology for the Pontiac V-8 has lessened the modernity gap between it and its competition.
Such developments have forced similar changes in other valvetrain components. Today, we find low-mass valves, uniquely shaped valvesprings, and lightweight hardware in virtually any engine designed to extract maximum power at high rpm. But one component of that combination, which is as critical as any other, is the lifter. Follow along as we explore the different lifters available for Pontiac engines and learn the effects modern technology has had on them.
Hydraulic Lifter Basics
A typical hydraulic lifter in an overhead-valve engine includes a main body and an internal plunger-and-valve assembly that relies on engine oil pressure to continually adjust valve lash to maintain constant contact of all the valvetrain components during normal operation.
Camshaft technology is continually changing and new developments are typically aimed at improving performance. One component that's often overlooked is the lifter, yet technology has played a large role in its development over the years. Follow along as we explore the major types on the market today.
While on the base circle of the camshaft lobe, pressurized oil from the lifter bore enters a feed hole and fills a cavity in the lifter body that's located beneath the plunger. As the lifter body follows the cam lobe and begins rising, valve-spring pressure transmitted through the pushrod compresses the plunger against its spring-loaded check ball, immediately isolating the lifter from the engine oil supply.
As the cam lobe travels toward peak lift, the lifter and plunger raise as a unit, lifting the pushrod, which in turn lifts the valve off its seat. Resistance from the valvespring pressurizes the oil within the lifter body, which causes a small amount to bleed outward between it and the plunger. This is referred to as "leakage" or "leakdown."
Once the lifter travels up and over the entire cam lobe and is back on the base circle, internal spring pressure causes the lifter to expand, forcing the plunger upward, which eliminates valve lash, opens the check valve, and allows pressurized oil to refill the lifter body cavity before the next lift cycle starts.
Hydraulic Lifters In Pontiacs
Pontiac's engineers incorporated hydraulic valve lifters into the development of its V-8 during the '50s, supplying each lifter bore with a relatively high volume of pressurized oil. Specific degrees of lifter-body-to-plunger clearance can be used to vary leakdown rate, and Pontiac employed various specific-rate hydraulic lifters for select street applications over the years.
The standard hydraulic lifter, like this well-used Pontiac unit, was developed decades ago and it utilizes pressurized engine oil to keep all components of the valvetrain under constant contact, ensuring quiet, maintenance-free operation.
In most instances, plunger depth was preset using a tapered rocker arm stud and corresponding adjuster nut. The combination placed the plunger in such a position that the lifter would function correctly in myriad conditions and with normal valvetrain wear.
As engine speed increases beyond its intended operating range, valvetrain components can bounce or "float." Pressurized oil immediately takes up the excess lash during the refill cycle, causing the lifter to displace a greater-than-normal volume of oil. If this amount is greater than the lifter's leakdown rate, the lifter can "pump up," holding the valve off its seat, ultimately limiting engine rpm and power output.
Hydraulic "pump up" can be controlled with lifters that feature limited internal plunger travel and an adjustable valvetrain, which positions the plunger near the top of the lifter body during normal operation. This produces a semi-solid hydraulic lifter that operates conventionally, but extends maximum engine speed by several hundred rpm. Hobbyists can find similar results converting their Pontiac's standard non-adjustable valvetrain to a fully-adjustable setup and adjusting the plunger into the body 1/8 to 1/4 of a turn down from zero clearance.