[Cliff R]

I really don't think there is that much difference between hydraulic flat tappet and HR grinds, or not as much as folks think.

We can easily mimic the power of a HR grind with a very well chosen hydraulic flat tappet cam topped with Rhoad's lifters and high ratio rocker arms. We did that test a few years back right on the dyno between the Crower 60919 cam and a custom ground Comp HR cam with 230/242/112 specs. It had .361" lobes and quite a bit more lift than the 60919 cam, but only made 3hp/4ft lbs more torque on the dyno in back to back pulls.

The Crower cam had 1.73 rockers on it, and Rhoads lifters, and actually made peak power 200 rpm higher in the rpms range than the custom HR cam.

On back to back pulls we saw 494hp/540tq from the 60919 cam, and 497hp/544tq from the HR. Then we put the high ratio rockers on the roller cam and started swapping intakes/carbs/spacers, and ended up making 514hp/567tq by the time we were done, so it did open things up for more power with some additional work

The test still shows how well a flat tappet cam works in these engines, and we can "tame" it some with Rhoads lifters and bring on big power with high ratio rockers.

We recorded 12" vacuum at 750rpms with the 60919 cam, and 13.5" with the custom HR, so you really can get it done with a roller cam with less seat timing. The Crower cam had 304/314/113 specs, and 231/240 @ .050". The HR was 284/296 seat to seat, 230/242 @ .050".

The test engine was my old 455 with unported KRE "D" port heads with 85cc chambers, so about 10.5 to 1 compression........Cliff