67Rocket

I have a 400 B short block with a crack in it, I also have a 400 G block in good condition, can the B block rotating assembly be used in the G block? I was thinking of boring the G block + .030 to .060 to make a nearly square assembly. I'm sure someone has tried this and was wondering how it turned out? Thanks

oldsmobiledave

The 400B is from a 1965 442. One year only and 45 deg bank angle.
4.00" x 3.975" bore & stroke


The 400G is the crappy 68-69 block. 39 deg bank angle.
3.870" x 4.250" bore & stroke


You can see the problems with your plan.

67OAI

I have seen the 400G block bored to 4.060 successfully. If you do want to use the 400B assembly, you would have to bore to 4.000" minimum. As stated above you will not be able to use the camshaft from a 400B in a 400G.

67Rocket

Thanks, only parts from B block would be crank, rods and new pistons. Have the parts and was wondering if anyone had tried this combo?

joe_padavano

Do the math. The short stroke crank in the small bore G-block yields 375 cu in with stock dimensions. Add to this the fact that you can't use the G-block pistons with the 7" rods due to differences in piston compression height. Yes, you can bore the G-block oversize - assuming you spend the money on sonic testing first.

67Rocket

Thanks Joe, so would boring the G block .060 and using the B block crank and rods be a workable combo?

joe_padavano

Those would still be custom pistons. And the displacement would still only be 386 cu in (3.87 + 0.060 = 3.930 bore vs. 4.000 on the B-block).

oldsmobiledave

No

joe_padavano

If you are absolutely dead set on using the G-block, then try to have it bored to 4.000 (that's 0.130" over) and use the original B-block pistons.

Personally, I would just get a 455 block, use the B-block crank and rods, and use 425 pistons, making it a 425. With either the G-block or the F-block, you will need the matching 39 degree cam.

67Rocket

Thanks for the useful information.