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Old 11-20-2025, 11:34 AM
Snowbound Snowbound is offline
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Join Date: May 2003
Location: West Kelowna, BC
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Quote:
Originally Posted by b-man View Post
6X-8 heads maybe 8:1, 6X-4 will be 8.5:1 at best.

Choose your cam accordingly.

I’d be looking for 1970 #13 400 heads, usually around 77 to 80cc chambers although advertised as 72cc. This will bump you up around 9.5:1.

Bonus - #13 heads won’t need any finagling to match up the center exhaust crossover to your Tri-Power, unlike any 1972 and later heads like 4X or 6X.
Thanks B-Man, I'll be on the look out for some #13 heads I guess. I was not aware of the crossover issue.

This is kind of a "placeholder" engine until I can get a proper 389/421 together. The car came with a non-original 389 block, crank and tripower intake, but was missing the heads, and front accessory brackets, bolts, etc. I figured it would be easier to just buy a complete drop in, known running engine with all that stuff attached, rather than try to piece something together.

Oh, and I should mention that I bought the Ames 1967 Ram Air manifolds, so any head choice will need the proper bolt holes to mount them.

Cheers,
Brian

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1965 GTO Coupe project in the works. PHS documented Mayfair Maize, Tri-Power, 4 Speed, 3.55 Posi