Quote:
Originally Posted by jr_ss
I think the P12 head is just an expensive piece of hardware that doesn't benefit you in anyway shape or form over a P11 head with the same cams. I have yet to see flow numbers for a P12 head. The only thing that supports this claim are the components in the head and slight changes in the casting. They have weaker valve stems(smaller diameter), require custom spring retainers and are more expensive to acquire. The only benefit are the cams are much better than the P11's but that doesn't matter if you're swapping them anyway.
You will need to upgrade your valve springs. You can run the factory P12 springs with the P11 inners for a cheap upgrade. They experience valve float in the higher Roma without an upgrade.
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This is 100% on point, I never recommend the P12 cylinder head due to the aftermarket available for it. A P11 head can easily out perform the P12 especially with our CNC porting that we offer.