Hot Rod Forum banner
1 - 1 of 1 Posts

15,651 Posts
HPE01 is an old time cam profile that uses more ramp duration between what passes as starting on the lobe ramp profile and the .050 point compared to the XE268H. The difference is for comparable performance at the crankshaft flange the HPE01 will want about .5 to 1 ratio increase possibly as much as a full ratio more. The point is getting the most torque and power as related to the tolerable compression ratio on the highest octane fuel available.

Neither cam is particularly idealized for a boosted engine regardless of that being mechanical or nitrous. The issue here is power adders greatly increase the volume of exhaust to be eliminated which falls back on adding a bit more duration and lift on the exhaust valve side of the cam.

These values are probably more nits than anything on the street where drivability, even of a performance motor, is often a bigger issue than hitting the highest numbers possible on a dyno. Your biggest constraint with a Pontic is the rods as Pontiac was a big user of cast steel rather than forged rods. The cast rods are failure prone under high power and RPM, so unless you know for sure this engine has forged rods the rods are going to set the limits as to what you can do with adding power. I always sweat rods, they are the highest loaded part in the engine and their failure is almost always a total loss of the engine and the money you put into it. Pretty much my minimum naturally aspirated street street engine not to exceed 6000 RPM would be rods that are 5140 forgings. For any kind of serious performance including boosted from street on up through the track my bottom choice is 4340 with its grade qualities going up with the beating they are expected to take. This is more important than the choice of cast to forged crank and more important than 4 bolt mains. Actually tge Pontiac cast crank will take an amazing beating.

Pistons are another critical point especially with todays octane fuels. Forgings are way more tolerant to detonation than casting including hypereutectic castings which are a long way ahead of ordinary castings.

1 - 1 of 1 Posts