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Could these be 3946074 Aluminum heads if the exhaust ports a 'D-shaped'? Could they be 14011077 heads? The seller is dragging his feet in sending me a picture of the casting no. (both are from 1974).
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I thought 074's were round ports (not D or square) *NM*
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074 exhaust ports are round
those are 076 or could even be a set that was welded upComment
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Look at the Winters foundry snowflake
Most likely they are 074 heads. It was common knowledge that the exhaust port floor was actually an area of REVERSE flow, so it was common to weld them up into a D shape. In addition, I don't think the D port heads came out until about 1976.
If you look at the winters snowflake on the D port heads, the ones I have seen are smaller and stand up higher than the 074 heads.
D port is actually a misnomer, it was more of a C port as it had a vane that stuck up from the short side (port floor)to reduce mixture reversion, unfortunately many porters did not realize that was good and ground it out.
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