Buick 455 intake manifold bolt 7/16 14NC ??

I went to multiple stores with one of my intake bolts to try and figure out the threads. I needed to but a tap and die.

Menard's a bust.

I went to ACE hardware and thought I figured it out but I want to make sure before I destroy the head.

I did match up a nut and threaded it on the bolt.

It was a 7/16 14NC

I bought both die and tap.

I'm trying to tgead the bolt in but then it gets stuck.... Before I destroy it ...

Is that the correct bolt size for the intake on a 455?

Thanks.

 

Earlier heads were 3/8" bolts. I think in 73 they switched to 7/16"...

 

Thanks....this is a later engine and I pulled out an old bolt and it matched the used ARP replacements I bought from a member. I just want to make sure the threads are correct on the tap and die I bought.

I'm thinking it is correct.

 

A rethreading tap is what you want to clean the threads.

 

It has a flat bottom. Try this tap before trying to rethread the hole.

 

67-69 are 3/8-16 455's were 7/16-14

 

any idea what the lenghts are for a 67 gs400/ like to buy a kit off of Toddsgs but not sure what i need. anyone?
Im seeing 3/8- 16 is this correct
thanks
johnny

 

Toddsgs will let you know what you need.

 

he's not sure either. doesn't want to sell the wrong bolts. ive asked already
cheers
johnny