[Hank]

Can anyone tell me what i'm gonna have to do to put a set of 670 heads on a 66 389?

[HO 67 BIRD]

I think youll need new pushrods & head bolts for center port at exhaust flange part of head

[tom s]

Just make sure you order 67 400 pistons as the valve reliefs are in a diff location.DONT get the pistons with 8 reliefs!Tom

[Goatracer1]

You can use your stock 389 pistons as long as you use a stock 389 cam if you are just trying to change heads. If you are rebuilding the motor by all means change the pistons to 400 cid pistons. If you are trying to run a high lift cam you will also have to change pistons.

[Hank]

What about the push rods?

[tom s]

Depends what your going to use for studs,rockers etc,sure you will need new but determine that after the engine is together.Tom

[Hank]

I was just going to use the studs and rockers that came on the 670's

[b-man]

Use the same pushrods and rockers that the '67 670 heads would have come with. The '66 389 pushrods and rockers won't work with the 670 heads.

Head bolts are different between 400 and 389 engines. Not sure if it's just the center exhaust side bolt that's different. I would try to use a complete set of '68 or later head bolts, some low-performance '67 engines still used the earlier 389-style heads.

[geeteeohguy]

Originally Posted by Goatracer1

You can use your stock 389 pistons as long as you use a stock 389 cam if you are just trying to change heads. If you are rebuilding the motor by all means change the pistons to 400 cid pistons. If you are trying to run a high lift cam you will also have to change pistons.

This^^^. As long as you stick with a factory cam or go only a bit larger, no issues. I did the reverse back in the day, installing standard 400 pistons in a 389 punched .060" to save money. Ran a pretty hefty Sig Erson Hi Flow 2 cam in that engine, with no issues, running the '66 389-421 093 heads.