1969 427/400 Exhaust Manifold Bolts

[Ned T.]

I'm installing my exhaust manifolds and the last two bolts in the rear on the left side bottom out before they touch the manifold. Its only by approximately 1/8" but still won't go in. I ran a tap in each one and it also bottoms out. All others on both sides went in fine. I can't imagine these two should be shorter bolts but I really don't know. I'm going to pick up a "bottoming tap tomorrow and try that. Any other reason they wouldn't go in all the way?

Thanks, Ned

[Terry M.]

Re: 1969 427/400 Exhaust Manifold Bolts

Crud and debris in the bottom of the hole?

[Ned T.]

Re: 1969 427/400 Exhaust Manifold Bolts

I can get a small screwdriver to the bottom but not the regular style tap. I think the "bottoming tap" will do the trick to clean up the last few threads.

Thanks Ned

[Joe L.]

Re: 1969 427/400 Exhaust Manifold Bolts

I'm installing my exhaust manifolds and the last two bolts in the rear on the left side bottom out before they touch the manifold. Its only by approximately 1/8" but still won't go in. I ran a tap in each one and it also bottoms out. All others on both sides went in fine. I can't imagine these two should be shorter bolts but I really don't know. I'm going to pick up a "bottoming tap tomorrow and try that. Any other reason they wouldn't go in all the way?

Thanks, Ned

Ned------


The manifold end bolts on 1967-74 big blocks used a special locking thread bolt which had a flanged head. The other bolts are non-locking and are standard hex head. Curiously, the end bolts are also slightly shorter than the other bolts.

[Ned T.]

Re: 1969 427/400 Exhaust Manifold Bolts

Joe, I bought replacement bolts from Paragon. Bad idea because they don't have a flange, but they do have a very slight shoulder. I'm going to go through the box from my engine builder but I think they were mismatched and not in good condition. I should also start looking for a good original set. I now see that the flanges on the front and rear of each manifold are thinner than the others, thus the shorter bolts. I also just checked the length of the stud that goes in the very front of the left side.....it's shorter too. Looks like ill have to switch all the bolts around and get the right lengths in the right holes. I love being in the garage till late !!!

Thank You, Ned

[Greg L.]

Re: 1969 427/400 Exhaust Manifold Bolts

Ned,

What if you just 3/16" or so off the end bolts?

I've had a my fair share of bad luck with Paragon's parts especialy the hardware. At best I've had to modify the fastener to work like I mentioned to you and at worse I've just thrown the new bolts in the trash rather than deal with returning them...

[Ned T.]

Re: 1969 427/400 Exhaust Manifold Bolts

Greg,

I'm going to save the Paragon bolts just to have around but I did find a set of correct bolts I'm going to buy. I will also let Paragon know that their bolts are not correct for the application they show.