670 heads and pump gas
I have a 67 GTO with a 69 400 in it with 4x-7h heads. Not the fastest 67 GTO on the road but it runs great on 91 octane. I'm going to try some 87 when I get back on the road soon after a year and a half of body work.
I have been thinking about going to 670 heads. I have heard conflicting stories about running pump gas with these heads due to the higher compression.
Can you run 91 octane with 670 heads or not? Anyone doing this?
Thanks!
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