nickmckinney

Yes the PI intake valve seat is 0.060" closer to the piston than the NPI valve seat (the valve stem is made this much longer to compensate) Then the PI valve has this 0.040" of extra lip on the end. So it ends up 0.1" closer to the piston than the NPI head. You can remove the PI valve lip in a lathe and gain 0.040" of clearance or install aftermarket valves.

NPI head spring retainer sits closer to the valve seal, so that is the problem with those heads and higher lift cams. You can install Crower +60 retainers to solve that problem on NPI heads.

Both heads have different problems, and the solutions are pretty easy too. The PI solution is to pull the heads and change/modify the intake valves. Its more work but its well worth it.

disposablehero27

What kind of cams would you recommend with the cobra's "b" heads with a d1sc procharger? should i be doing fly cut flat tops still? or go dished with cuts?

wolverine8490

Yeah, I have done a lot of research on here. Looks like if you do not have the cams degreed it could cause issues (but it is that way with any cam).

Then again, I always turn the motor by hand 2 full rotations to verify that major damage will not occur after timing an engine. Seems like there are a lot of people on here that run CMS stage 2 cams and have no issues.

I think I am still sticking with CMS. I have heard nothing but good things about them.