The various types of lifters...
The various types of lifters available on the market today include the hydraulic flat-tappet (left), solid-roller (center), and solid flat-tappet (right). Because the pushrod cup sits much lower when comparing this flat-tappet solid lifter to the hydraulic, longer pushrods are required.
Taylor uses Crower's solid lifters, of which he says, "Oil almost the same amount as those originally designed by Pontiac engineers-3 gallons per hour through the pushrod, so no restrictors are required. They also feature a 0.024-inch-diameter hole in the lifter face that pressurized oil flows through to lubricate between the lifter face and cam lobe without reducing oil pressure. Some solid-lifter manufacturers install the pushrod seat 0.100-0.150-inch lower than that of a comparable hydraulic, and longer pushrods may be required, but you must still check."
"We only use Crane or Crower full-roller rocker arms and their posi-locks and ARP rocker studs. Valve lash ranges from 0.008-0.020 inch cold, and when setting lash, we use 30-weight oil on the threads of the posi-lock barrel and moly-based lube on the setscrew for smooth torquing." He adds, "The ARP stud offers a flat mating surface, allowing full contact of the setscrew. This combination provides a positive lock-even with stock valve covers and gaskets-and a valvetrain that shouldn't require readjusting."
Rolling With A Hydraulic
Q. What typical advantages do hydraulic-roller camshafts offer, and what types of modifications are necessary for installation into a Pontiac V-8?
A. It stands to reason that reducing internal engine friction can translate into additional power. When applying this theory to camshaft design, we find that roller bearings contain a number of advantages beyond reduced friction. Combine this with low-maintenance hydraulic operation, and it isn't surprising that hydraulic-roller camshafts are so popular today. Wanting to know more about hydraulic-rollers, we contacted Dave Bisschop of SD Performance in Chilliwack, British Columbia, Canada.
Bisschop tells HPP that hydraulic-roller camshafts are currently the most popular choice for performance applications. "There really aren't any negative side effects. You're able to achieve a lot of area under the curve without the excessive valve overlap that normally bleeds off cylinder pressure. Because of this, hydraulic-rollers produce better power numbers and offer improved idle quality and low-speed street manners over flat tappets. But you can't necessarily compare the 0.050-inch duration numbers of the two. The roller's lobes are far more aggressive, so 0.200-inch-lift numbers offer a better comparison."
Converting to a hydraulic-roller camshaft is fairly straightforward, and though a standard thrust plate and timing chain set can be reused, custom-length pushrods roughly 0.400-inch shorter than standard Pontiac pieces are required. Bisschop says that valvesprings like those used with aggressive flat-tappets are adequate. "We increase spring pressure slightly by reducing the installed height about 0.030 inch, which typically raises the pressures 10-15 pounds. For most applications, 130-140 pounds of seat pressure and 320 pounds of open pressure is adequate. The lifters are pretty heavy, so we find a safe limit is around 6,000 rpm. If the engine needs to spin higher, we'll upgrade to such items as titanium retainers and select springs with a higher rate.
"We've seen problems with roller lifters not properly pumping up in the past, but the situation seems to be much better today," says Bisschop. "The lifters fit the block fine, but you'll need to modify the stock valley pan to clear the link bars on the lifters. The roller cams are billet steel, and a cast-iron distributor gear will ruin the distributor drive gear on the camshaft, so we opt for BOP's composite gear as it outlasts a bronze gear many times over. I also suggest positive lubrication on the gear by drilling the internal oil plug, but it's still a good idea to periodically check its condition since wear can affect ignition timing."
Due to its steel construction, initial break-in isn't required, and today's oil-quality related issues don't apply to a hydraulic-roller. "There shouldn't be any wear," says Bisschop. "So once the valves are set, a hydraulic-roller is virtually maintenance free for the life of the engine. And with improved low-end and midrange, you can achieve maximum performance with less rear gear and converter while improving idle quality. All of this is what makes hydraulic-rollers ideal for street/strip applications."