block Id
 

I have a sbc with the casting number 3914638. It has a TII30DF stamped on the pad at front of block. Book says the number is a 327, 4 in bore but it measures 3.875 like a 307. Numbers on front indicate a 1968 307. It is a big journal crank. Could this have been intended to be a 327 and instead is a thick 307? Has not been cleaned or sonic tested so I don't what that looks like. Let me know what you think.
Mark

Re: block Id
 

Mark, several sources list the 3914638 as a 307 block. Hope this helps. -Al

http://www.probuildamerican.com/tech...5327350383400/

Re: block Id
 

GM did use some blocks for 3.875 and 4.00 such as the 3789817 is a 62-67 327 block but I have one that is 3.875 and was used with a 3.00 crank for 283 in 1966. This makes for a very thick cylinder wall but leaves a lot of room to bore.

Re: block Id
 

I would still have it sonic check'd before puting $$$$ into it.

Re: block Id
 

Mark…A 3914635 or 3914636 is a 1968 307 and are 3.875 bore, possibly the last number is filled in with casting making it into an "8". There are 1968 blocks with a casting number 3932386 that are 4.00 bore. Are your intensions to bore it to 4.00? Wondering what numbers are cast into block behind the timing cover? Hope this helps…Maurice.

Re: block Id
 

Could you imagine sonic testing and filling that block and building the ultimate 283 out of it?283 blocks are getting pretty rare. 307 castings seem to still be out there.There is definitely a use for that block.Another block number is 3870020 and 3870024. Set of space saver main bearings might be difficult to locate,however.

Re: block Id
 

3914638-----1968 2 bolt main truck block 327
3914636------1968 2 bolt main 307