400 Heads

[worldbob]

I have a 1970 YS 400 in my 66 Tempest. I was going to do a header swap last weekend, but the heads don't have the outer exhaust bolts tapped, Is this normal for Pontiac?

[bdk1976]

What heads do you have? There were a few heads from the early 70s that were missing this hole. Here is one solution to the problem:

http://www.spottsperformance.com/headLbracket

[HOTROD64-STOCK69]

If the casting is there then you should drill and tap the heads.

[worldbob]

Cast # is 11.

The material is there. Looks like I need to drill and tap all four holes :mad:
It's going to be a pain..... might be easier to pull the heads to do it right???

Thanks for the help!

[HOTROD64-STOCK69]

Yep, pull the heads and bolt on a maniflod, use a transfer punch to locate the center. The hole in the manifold is much larger than the 3/8 bolt that goes through it because the factory gives shrinkage room for the manifold. If you are a novice at this a machine shop is money well spent on this project. Mike

[69projects]

Agreed on the Machine shop. You need a "Bottoming" Tapp to get the threads all way down and getting the hole square and centred would not happen on MY workbench!

[worldbob]

Thanks for the advice......

Looks like I'm pulling the heads tonight. Machine shop here I come!