Help, What engine do I have???

[hotrod_chevyz]

Those heads were used in 1967 on 400's. They are typically known as "1.92's".

1967 "big car" with 061's = 325-333 HP

1967 "small car" with 061's = 290 HP

1967 "XW" block = 325 HP

> C237 = March 23rd, 1967.<

It could be the original heads with a different block. But i dont think so.
Im thinking the engine is a 400 cid from 1967, born in a "big car", later transplanted into a "small car" (yours). But due to the parts availability in 1967, it still could be original. Pontiac may have used up all the 290HP blocks and stuck the car with a block meant for a bigger car. It wouldnt be the strangest thing ive seen.

[Hurricanes7]

The answer is................................................ .....400! I found the casting number behind the #8 cylinder after taking the hood off. It is 9786133 with the XW stamp, 061 on the header and C237 also stamped on it. The casting number is what verified it. 1967 325hp engine. When I bought it from the guy, he also had a 68 convertable Firebird 400 that was minus the engine, he said he bought it that way and had been lookiing for a 400 to put in it, opps! Now to replace that Super Turbine 300 tranny they put in their.