What SBC do I have.

[Jeff Stout]

Receive a free sbc short block. Looked into it and it has a 1178 crankshaft. I thought score. Went pad and it had V1008TDX. It showed 307 2 bolt. Bore measures 4 inch, but the block is a 4 bolt main.010 casting. What do I have?
A poor man's 302?

[Cdncarnut]

What is the casting # and date of the block?

[Alan Roehrich]

Well, the 010 four bolt main block is a 350. I'd have to dig out my crankshaft manuals to say on the crank. But if you have a manual that says that number is a 3" stroke, then you have a 302. If it is a 307 crank, that's 3.25", making what you have a 327 large journal cast crank. Also a "combination" of parts.

[Jeff Stout]

It shows 1178 is a 302. Checking stroke shows 3 inch. Thestamping of TDX shows 1972 307. I will get to shop and check date and complete casting number.

[Jeff Stout]

Also reading I found that a 307 is 3.875 bore and most blocks can go 125 overbore.

[Alan Roehrich]

Originally Posted by Jeff Stout

It shows 1178 is a 302. Checking stroke shows 3 inch. The stamping of TDX shows 1972 307. I will get to shop and check date and complete casting number.

The stampings mean different things depending upon the year of the block and production. If the block is not a 1972 production block, TDX does not denote a 307, and being on a 4 bolt main 010 block, it's obviously not a 307 two bolt main.



I do not recall a 307 built on a 350 (010) block. Most 307 blocks would not do well at 4.00" bore. If you have a 302 crank in a 307 block, you'd have a large journal 283.


It could possibly be a service replacement short block. Or, most likely, someone wanted a 302 and didn't have the original block, so they put a 302 crank in a 350 block.

[Cdncarnut]

Originally Posted by Jeff Stout

It shows 1178 is a 302. Checking stroke shows 3 inch. Thestamping of TDX shows 1972 307. I will get to shop and check date and complete casting number.

The crankshaft is definitely 302.

The T on the engine stamping usually indicates a truck block.
TDX 1972 307 van & bus 135HP 2 BBL C-10 & 1500

The original Z28 302's were 327 blocks with 283 cranks.
3" Stroke, 2" Rod Journal and 2.3" Main Journal with a 5822 casting number
The 1178's had a 2.1" Rod Journal and a 2.45 Main Journal.

The 307 block had the a 3.875" bore, while the blocks used for the 327 and 350 302's had a 4" bore
Engine displacement would depend on the bore and I am not sure how much the '72 307 block bore could be enlarged. It would have to go 0.125 over to make a 302.

I cannot find a 4 bolt 307 block in my literature, but that does not mean that they did not exist, as I have come across some weird stuff...

Hope this helps.

Now back to getting my trailer ready for my first race of the season.

[Jeff Stout]

I had my employee read the stamping. Never knew he xould transposed. How about TXD NOT TDX. Makes the block a 1975 350 4 bolt.
Thank you for everyone taking the time to respond. Wild goose chase over 2 letters.

[Cdncarnut]

That block, with the 1178 crank is a 302...

[Barry Polley]

https://www.ncrs.org/ok/LIME_BOOK_2018.pdf

Most complete book I know.

78 307 the four bolt puzzles me unless GM was low on 2 bolts…