Grabbin' Asphalt
5 Year Member
Oh, I don't know about that. I've got a set of GT40X's on my 331 and am quite happy with them. Car pulls strong all the way to red line and the heads are about as direct bolt on as you're going to get. Not the performers that the Trick Flows or AFR's are, but still comparable...and still a step above the GT40/ GT40p's.
And don't be fooled, refurbishing a set of GT40/GT40P's can break the bank in a hurry. When all was said and done, my GT40X's only cost me about $200 more than a set of GT40 iron heads after the necessary machine work and valve spring upgrade.
Also, the pedestal mounted rocker arms only become an issue at sustained high RPM. The stock ECU cuts fuel at 6,250RPM anyway, so it's really a non issue for 95% of owners.
Comparative AFR's and Trick Flows will make slightly more power, but if you've got to buy stud mounted rockers, or longer pushrods, they can end up being a fair bit more expensive. If you've already got the pedestal mounted roller rockers and can find a set of GT40X heads for a good buy, they're well worth the investment.
Well said, I think those are great points also money into them is the key.