C2 66 Some 'Net sites list 3855961 block as 427

[Tom D.]

Not in Alan Colvin's (first edition) books, but at least two places on the internet lists the same casting number as 396 and 427.

www.mortec.com for example, on their big block casting numbers page:

3855961....396.......65-66...2 or 4 bolt
3855961....427.......66......2-bolt

Strictly due to this, a local hot rodder claims he has a 66 Corvette block in his 396 1970 No-Va-SS, despite the fact it's stamped with the "IA" code, which translates to Chevy Passenger Car, 325HP.

Were there really 427s made from this block? Were any of them 4-bolt blocks, either 396 or 427 4-bolts?

Thanks
Tom Dingman
4889

[Jack H.]

Re: C2 66 Some 'Net sites list 3855961 block as 42

The Mark IV BB began life intended for 427 cu in displacement. Some believe it was a 'strategic' decision to bore the block 'small' for its debut as a 396 due to the 'good neighbor' policy GM adopted that placed limits on engine size versus car body size....

Bottom line, there's enough 'meat' in the cylinder wall of a conventional 396 '962 block to take it up to 4.25" and install standard 427 pistons without affecting the block's water jacket integrity. The '961 block was pretty darn close to the '962, so it doesn't surprize me that it's a well known fact '961 blocks WERE used in 1966 bored out and configured for 427 engines.