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624 castings are in general, the worst heads that GM made. Average flow, but VERY crack prone. Later hd versions have a diamond shape cast on the outer side. They are less prone to cracking..
 

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Like "882", there are more than one "624" (as others have already said). One is the "light" casting, the other, "heavy". Flow from either is not real good... But the heavy castings are pretty tough.

To identify, the "light" casting has scalloped areas along the lower edge where the bottom row of head bolts "live". The "heavy" casting will have no scallops, and probably a single "notch" with a long "straight edge" where the lower row of bolts are.

FWIW

Jim
 

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Discussion Starter · #5 ·
they be 462624, 202/160 82 marine heads. wanna put on 80 4blt 350 3/4 tk w xtrem energy 274 cam headers 2 1/4 exaust to flowmasters w 3 in out. also have steel crank and rods from same marine 350.
 
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