1967 427/390 L-36 Exh. Manifold Bolts

[Owen L.]

I am replacing the hardware store bolts and split washers that were on my '67 L-36 exhaust manifolds and am looking for confirmation that these from AMK are appropriate in appearance and size. This car is not judged, I just like it to be kept or returned to as original in appearance as I am able.

I have French locks for the end ports of the manifolds.

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Thanks for the feedback!

[Leif A.]

Owen,
Weren't the stock bolts 1 1/4" in length? Don't know if the extra 1/16" would make a difference (bottoming out before tight).

[Gary B.]

Owen,

That AMK bolt is odd to me in one way. This is how it is described in an old AMK catalog.

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Compare that to the AMK bolt for SB applications.

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Notice that for the SB bolt, AMK lists the GM part number 3733130. When AMK lists the GM part number, it’s been my experience that the AMK item matches the dimensional specifications of the GMitem. Therefore, for the SB bolt I’d expect the AMK bolt to be the same length as the GM bolt. But for the BB bolt you’re looking at there is no GM part number listed in the AMK description. That suggests to me there is some slight difference between the AMK bolt and the GM bolt. Maybe that’s the 1/16” that Leif mentions. This is total speculation on my part.

Gary

[Owen L.]

Thank you Leif and Gary for your concerns about the length - this is exactly what I was hoping for.
I think I should mock up the manifolds to the engine and measure the max. bolt depth from the flange surfaces. (Engine is out of the car, rebuilt, and on its way to being dropped back in this summer.)

[Owen L.]

Just a follow up:
I decided to order the AMK bolts and figured I could grind off a 16th if needed.

There was no need for any worry. You can see below that a new bolt and an original from my '72 BB are the same lengths (within ~0.005"). The differences I can see are that the original bolt's head's radius starts just outside the outer ring of the maker's mark. The new AMK bolts start the radius further away with the result being a slightly different appearance and longer side "walls" where the wrench registers than originals. Otherwise, I think they are an OK substitution for original GM.

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