The benefits of hydraulic roller (HR) lifters are well documented, but until now, they have never been widely available for the traditional Pontiac V-8. Comp Cams has responded with a top-notch part, and PHR has the test results to show the bottom line.
HR lifters have the capability to outperform traditional flat-tappet designs due to the reduced friction and added performance of a roller tip. Like a solid roller, the ramp angles of the camshaft can be much more aggressive than a flat-tappet design, allowing the valve to open and close at a much faster rate. This exposes the cylinder to the port for a longer time, resulting in increased efficiency and the production of more power.
The maintenance requirement for a HR lifter is identical to a hydraulic flat-tappet, in that servicing is not required at all once lash has been correctly set. Use of poly-locks is mandatory, and shorter pushrods must also be used, since the new design lifter is taller than a standard flat-tappet piece. Shorter pushrods mean less deflection and therefore a more stable valvetrain, so this necessary part change is also a benefit.
Setting initial lash on a HR is accomplished by first ensuring the lifter is on the heel of the camshaft. Once tension is felt on the pushrod (by pushing the rod against the lifter cup by hand so its spring tension can be felt), the poly-lock is turned until it touches the cup once the up-and-down free play is removed. One more sixth of a turn (one "flat" of the hex head) is enough to make the necessary preload adjustment. Then, both the nut and adjustment screw can be tightened simultaneously from 25 to 30 ft-lb. Once accomplished, these settings should never require readjustment.
The Pontiac version of the HR cam is slightly different than other Comp Cams or OEM HR designs. Factory HR cams are made from a dedicated core that is the same material as a regular hydraulic cam. Comp Cams decided to use their readily available steel billet core, which has the appearance of a solid roller cam. This means you'll need to install a bronze distributor gear, which is no big deal. Two different inner diameter bronze gears are available, so measure your shaft diameter before ordering.
Development of these pieces was done with the assistance of Rock 'n' Roll Engineering, and the results we've obtained were with real street engines, although race-only versions have shown an even greater advantage for the HR lifter. We felt that sharing real-world results with the readership would be of the greatest benefit.
All of our dyno testing was done at the Westech Performance Group in Mira Loma, California. Regular readers will recognize John Baechtel's facility as one we've visited frequently, as Westech's equipment and personnel are intimately familiar with the rigors of back-to-back research and development testing, and have established themselves as some of the premier dyno dogs anywhere.
The first engine tested was an Edelbrock-headed 400ci Poncho. Compression was a very-streetable 8.5:1 with the large 87cc combustion chambers, and the hydraulic flat-tappet cam lobe tested was Comp Cams P280AH-10. The specs on this cam are 232/237 degrees at .050-inch lift, and .531-inch lift with a 1.65:1 rocker. Advertised duration numbers on this cam are 280 degrees on the intake side and 288 on the exhaust. A slightly bigger HR cam with .540 lift and 288 degrees of duration was chosen because the new profile design tames idle quality. Duration at .050-inch lift was 244/245 on the intake and exhaust, respectively. It's possible to add a little more duration without sacrificing driveability or mileage when you step up to HRs. We used the same lobe separation angle to see the affects on the powerband.
The rest of the 400ci Poncho was standard street fare. A Speed Demon 750-cfm carb (with 86 primary and 91 secondary jets) topped an Edelbrock Performer RPM intake manifold that had been ported in-house at RRE. SRP pistons filled the holes, and were sealed by Sealed Power rings. The upper ring gap was set at .016 inch, and a gapless second ring was used. This powerplant was designed to make great power on pump gas, while maintaining a civilized idle and generous vacuum (never less than 11 inches).
You'll see the flat-tappet had a slight torque advantage at 3,000 rpm, but then the HR takes over at 3,800 and makes a very strong broad amount of torque until we quit the test at 5,900 rpm. While the hydraulic never made 500 lb-ft, the HR cleared 500 at 4,400 rpm and maintained 490-plus to 5,500 rpm. Amazingly, it dropped very gradually. The hydraulic flat-tappet cam dropped off much quicker.
We also tested a 455ci Pontiac that had a similar buildup. SRP pistons, Total Seal rings, and the same Comp Cams HR camshaft were teamed with RRE-modified Edelbrock heads and intake, stock connecting rods (properly prepped with ARP bolts), and a Quadrajet carburetor that made 487 real horsepower. It has averaged 12.9 mpg in a stock '70 GTO convertible, and is capable of running high 11-second quarter-mile times. This pump gas 455 cleared 532 lb-ft of torque at 3,000 rpm and maxed at an amazing 572 lb-ft at 4,000 rpm. Like the 400, it never made less than 11 inches of vacuum at idle. The ability to make so much low rpm torque and the quicker acceleration will nearly snap your old Pontiac's axles. It will certainly put a big smile on your face.
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 The Cam Pro Plus from Audie...  The Cam Pro Plus from Audie Technologies was used to verify all camshaft specifications. The ease and accuracy of this tool are an invaluable aid in researching and developing camshaft profiles back-to-back. |
 The new Comp Cams hydraulic...  The new Comp Cams hydraulic roller lifters use a steel billet core on both solid and hydraulic roller camshafts. Seen here installed in a Pontiac engine, the camshaft requires a bronze distributor gear, also offered by Comp Cams. |
 When compared to a traditional...  When compared to a traditional hydraulic flat-tappet lifter (lower), the roller lifter is a much taller design, calling for shorter pushrods. The shorter pushrod deflects less, adding to the stability of the valvetrain. |
Hydraulic Flat Tappet |
 Comp's New Hydraulic Roller...  Comp's New Hydraulic Roller The HR met the power numbers of the hydraulic flat-tappet just past 3,500 rpm, and pulled away from there. The HR torque numbers cleared 500 lb-ft at 4,400 rpm and maintained the high grunt factor past 5,000. The HR-equipped Poncho kept making 500 lb-ft until 5,200, and maintained high 490s until 5,500. The hydraulic flat-tappet design never made it to 500. It was in these same 5,000-plus rpm points where horsepower differences were most obvious too. The HR kept making power almost all the way to 6,000 rpm, while the similarly-sized hydraulic flat-tappet began to level off. Without sacrificing anything, the HR made more power on the top end. |