[ejgoat]

Can you put 670 heads on a 66 389 block

[1_Wild_Cat]

Yes.

[ejgoat]

I was told they would not work on a 389

[1_Wild_Cat]

I don't think what you were told was accurate. The head bolt arrangement is the same and the the intake manifold bolt pattern changed in 65. There may be some compression issues with modern fuel if you aren't making changes to the pistons too. I think by 66 the potential of valve to piston contact that resulted from a change in the head angle is already taken care of (but I could be wrong - so you would need to make sure you use the right piston).

[PontiacJim1959]

Originally Posted by ejgoat

Can you put 670 heads on a 66 389 block

Yes and no. They will bolt up. 1967 and up has a different angle. The valve notches in the 389CI pistons will not match, and that is where the problem comes in.

Yes, they can be used if you do not go crazy with valve lift. I believe you won't have any issues if using stock lift cams. If you go with a larger cam, then the valves may strike the pistons, so always a good idea to check, even with stock cams, your valve to piston clearance.

[1_Wild_Cat]

Thanks for the chiming in with the clarification and pics Jim. I initially answered thinking only of using the block. But when I did something similar years ago I rebuilt the short block with new pistons so...

[ejgoat]

So the right pistons are the answer, give me a clue to the right pistons if you can, would 400 pistons work

[Old Man Taylor]

Bore it to 4.120" (stock 400) and buy standard 400 pistons. However, you can run at least up to an "H" (744) cam with your current pistons. At least it worked for me.

[Old Man Taylor]

Also, if you have the pistons out I would grind new reliefs in the cylinders. The pre-67 valve reliefs in the block were at 4 O'Clock or 8 O'Clock depending on the cylinder. With the later valve angles the factory moved the reliefs to 3 O'Clock and 9 O' Clock. This is primarily to unshround the intake valve as the larger valve (and new angle) put it closer to the cylinder wall. Am I making any sense, I'm tired.

[PontiacJim1959]

Originally Posted by ejgoat

So the right pistons are the answer, give me a clue to the right pistons if you can, would 400 pistons work

Yes, most will use the 400CI pistons with the 1967 and up heads. Then you will have no issues and can order pistons as you would for any 400CI set-up.

The 389CI will need a .060" overbore to use the 400CI pistons, and you may want to add the scallops to the top of the bores for better flow on the valves. Some of the members here suggest to sonic test the block as a precaution to make sure you have enough cylinder wall thickness to go .060" over, but it should not be a problem.

I am sure you can have a custom Ross 389CI piston made through Butler. Forged, and a little more money being custom if you don't want to go .060" over.

With the 400CI piston, you can select, cast, hypereutectic, or forged, and will most likely want to go with a dished D-shaped piston crown to match the 067 chamber shape and lower compression for pump gas to a safe 9.0-9.3 compression. - unless you want a high compression engine and plan on using race gas or an octane additive.

If you live at a high altitude, then you can increase compression and still run pump gas.

I enclosed a magazine article that outlines the '67 heads/top end on a '66 389CI.

[shuffster]

To follow up with this discussion, Will the 389 valve covers work on the 670 heads with the 068 cam? Need double gaskets?

[b-man]

Originally Posted by shuffster

To follow up with this discussion, Will the 389 valve covers work on the 670 heads with the 068 cam? Need double gaskets?

Doubt that double gaskets would be enough, more likely need to look into a 3/8” or 1/2” spacer.

[69hardtop]

Originally Posted by shuffster

To follow up with this discussion, Will the 389 valve covers work on the 670 heads with the 068 cam? Need double gaskets?

Nope, won’t work without a good spacer. I tried doubled up gaskets and have a nice set of ruined valve covers......