I have a stock 1975 455 in my car right now. I bought a set of 1970 heads that are in good shape but need to be gone through. They are in my garage and already paid for. I just found a guy selling 1972 stage 1 heads near me. These have been cleaned and checked for cracks but need to be rebuilt and a valve job. Which would produce more power? And how much? If the stage 1 produces more power, but only a few horsepower, it might not be worth the money he is asking. On the same thread, if I put larger valves in my 1970 heads, will they be the same as stage 1 now, or are there other differences?
Based on everything I've learned, go with the 70s and properly redo them. You're already up several ccs with the 70 heads
What is your budget? If rebuilding either set is the same amount, putting bigger valves in the 70 heads and the minimal machining to make them actually work would be quite a bit more. You could shave the 72 heads, which are already bigger factory valves and unshrouded and get better flow. The real secret to a good flowing set of heads is the cam. You'd need to swap in something like a TA212 to get some better flow and raise the RPM range a tad.
The std. & S1 heads are the same casting - The difference is the valves and related machining to answer your initial question. It seems like it's simply whatever the conversion cost is (machining + buying valves) on the '70's vs. the cost of buying the '72 heads & shaving them to get the same chamber volume as '70 (which may need to be milled anyway just to clean up) and then whether that cost, whichever is less, is worth the 16 HP (more w/a better cam?). Unfortunately, you won't recoup much if anything selling the '70 heads. Probably worth it IMHO (obviously not my money so easy to say), it's just which is the less expensive option. I'm also not sure, but would suspect that the S1 conversion should be done by a machine shop familiar with doing it, but maybe that's not necessary whereas any decent shop could simply rebuild/mill the '72's so there could be additional cost sending the '70's to the "right" shop and either way, whatever the extra turnaround time would be to do the conversion.
I have a set of ported 72 Stage 1 heads on my 70 motor and didn't notice any difference in power between the ported 70 Stage 1 heads.I have 3 sets of 70 Stage 1 heads on my shelf, plus Aluminum Stage 2 heads.When I do a head swap,I'll be going Stage 2 for sure.
So, let me take a step back to see if I even should go down ANY of these paths. What hp gain would I see from swapping out my stock 1975 heads for the stock 1970 heads? If it is 10hp, great. Then I can assume 26 more hp if I swap stage 1 heads for the 1975 heads, which would be worth the $400 the guy is selling them for. But as Larry pointed out, maybe I should just save for aluminum heads if they will produce 40+ HP over 1975 heads and the machine work for the stage 1 heads will be significant anyways. Problem is, that will take me about a year to save up $2500 for aluminum heads and I want my car to go faster now LOL. Maybe I save for aluminum heads for next year but swap out my freeway rear end gears for 3.55s. Swaping out the gears will give my car some acceleration equal to at least 10hp I assume? This car is driven on the street 80% of the time, 10% freeway, and hopefully soon 10% at the drags. 1971 Skylark with stock 1975 455 and stock turbo 350 transmission.
Someone on Facebook is selling Stage 3 iron heads with 1.65 roller rockers, sp2 for 3600. Came off 9sec 464.
Hopefully you have headers to take agvantage of the flow. Then some nice manderal bent exaughst. Get the head with the smaller chamber. Run them wirh maby a valve and seat grind. Then dave up for new cam and stage 1 se alumin heads. Go stg 2 se heads if u want new headers. Comes down to money patience and do as much of the work your self.
