Bore is 3-7/8" the same as a 283, stroke is 3-1/4" the same as a 327. However, IIRC the 307 crankshaft counterweighing is different that a real 327 LG crank. I hope this helps.
Bill

 

Thank you Bill, it does.

 

I don't know if it is true or not, but I remember reading somewhere that the 307 came about because from 1967-69 to make the Z/28 302 they used a 327 block with a 283 crank, so Chevy ended up with a lot of 283 blocks and 327 cranks. They put these 2 together after the 1969 model year started and that is how the 307 came about.

 

I don't know if it is true or not, but I remember reading somewhere that the 307 came about because from 1967-69 to make the Z/28 302 they used a 327 block with a 283 crank, so Chevy ended up with a lot of 283 blocks and 327 cranks. They put these 2 together after the 1969 model year started and that is how the 307 came about.

I do believe there were more than 602 307's made.
The 307 uses a large journal cast iron crank. So the 307 block and crank are made for each other, not left over 283/327 parts.

Cars and trucks were getting heavier and had more accessories, so a larger hi-torque engine was made, the 307 was the entry level, the 350 in at the top and in 70 the 400 came about as the top spot.

BBC's were considered performance engines even though they made a 396 2 bbl in 68-69

 

Great info guys, thanks!

 

Just did the math on 3.875" bore 3.25" and came up with 316 cubic inches!! Are those figures accurate? A 3.875" bore with a 3" stroke comes out to 301.44 cubes (the historic 302).

alan

 

Just did the math on 3.875" bore 3.25" and came up with 316 cubic inches!!
alan

'Fess-up' Alan ... you just fiqured you'd be boring it .060" over anyway and then it would have 316 C.I.

 

Alan, check your calculator battery....
3.875" DIA/2 = 1.9375" radius
(1.9375)² = 3.7539 in/sq.
3.7539 in/sq X 3.1416 (pi) = 11.793²/in.
11.793²/in. X 3.250" = 38.328³/in.
38.328³/in. X 8 = 306.6³/in.

:beers:

 

Alan, check your calculator battery....
3.875" DIA/2 = 1.9375" radius
(1.9375)² = 3.7539 in/sq.
3.7539 in/sq X 3.1416 (pi) = 11.793²/in.
11.793²/in. X 3.250" = 38.328³/in.
38.328³/in. X 8 = 306.6³/in.

:beers:

It's not my battery, it's my brain. I multiplied Pi by the bore instead of squaring the radius. Ugh...but I am petitioning my college to review my physics tests as when I took the courses, matter couldn't exceed the speed of light but last week, that was proved false. I might just pick up a few points and raise my GPA.alan

 

Good luck!
I tell people here as in everybody sending electronic mail,
"Electrons move at the Speed Of Light, but, not in this building."

 

Hey Guys while we are on 307s I read somewhere that the 307 block had a low nickel content and is not a good block to rebuild or use due to this. Better off starting with a 350 block. Is this true?

 

You're better off starting with a 350 block due to the .125" larger bore.

AFAIC, the Chevy 307 is the bastard red headed step child of the Chevy V8 engine family...

 

You're better off starting with a 350 block due to the .125" larger bore.

AFAIC, the Chevy 307 is the bastard red headed step child of the Chevy V8 engine family...

And the 305 is it's conjoined twin.....but with a crank rods you can at least use....As in conjoined twins, sometimes they have to share stuff while the other one gets the short end of the stick.

 

The 307 was created in answer to the increasing pressure for control of emissions; the smaller bore resulted in a lower (more favorable) bore/stroke ratio, which slightly reduced NOX emissions. As previously noted, it was created from scratch (new block, new crank).

:beers: