altenator Bolt hole to small ? head problem

[Doc Voodoo]

ok My altenator bolt the big one will not go in. I had a pair of 289 heads worked so its not my original heads. The problem is the bolt hole is smaller then on the originals were the altenator bolts to the head. Why would a 289 head be diffrent and is it ok to drill out and tap it bigger

 

[66P51GT]

ok My altenator bolt the big one will not go in. I had a pair of 289 heads worked so its not my original heads. The problem is the bolt hole is smaller then on the originals were the altenator bolts to the head. Why would a 289 head be diffrent and is it ok to drill out and tap it bigger

It would be easier to replace the bolt with one that works vs. drilling/tapping the existing hole in the head (no pun intended).

 

[Ronstang]

Are you sure you are in the right hole? The holes actually got bigger on later model heads due to air passages and require a bushing to use a bolt in them so the largest bolt used for an alternator is the one that belongs in the 289 head.

 

[Doc Voodoo]

The original Heads are 1966 vintage. The heads on Now say 289 right in the middle of them. The hole for the altenator bolt is a little larger on the original heads that came off the engine . The new heads holes are just a little to small to fit the original altenator bolt and yes its the right hole . Its in the same location on both heads. The new bolt is OEM becouse I got a new one from NPD and it matches the old bolt that came off the car.

Could it be an early head maybe for a generator not an altenator Car ?

I was telling may DAD watch it be some Rare early 289 head worth alot of money And I destroyed it by drilling it out LMAO

 

[Ronstang]

Have you tried running the proper size (size of bolt) tap into the offending hole to make sure it isn't just crusted up or a bad original tap job? Something is a amiss here since all 289 early 302/351 heads have exactly the same accessory bolt pattern and sizes.

 

[D.Hearne]

Some of the earlier 289 heads had 3/8 acessory bolt holes.The later had 7/16 holes for accessories. Just have the offending hole drilled and tapped for 7/16 NC.