A.I.R. Bracket to Intake Manifold Bolt

[James H.]

On my 1970 LT1 engine....

The cast iron A.I.R. bracket I understand from the TIJM has a bolt, at the front right side of the manifold that holds down the cast iron A.I.R bracket and was painted orange with the engine. Because the cast bracket is about 3/8" inch thick, I am guessing that bold is longer than all of the other intake manifold bolts. Does anyone know what the proper length of that manifold bolt is and the proper head markings?

Thanks

Jim

[Joe L.]

Re: A.I.R. Bracket to Intake Manifold Bolt

On my 1970 LT1 engine....

The cast iron A.I.R. bracket I understand from the TIJM has a bolt, at the front right side of the manifold that holds down the cast iron A.I.R bracket and was painted orange with the engine. Because the cast bracket is about 3/8" inch thick, I am guessing that bold is longer than all of the other intake manifold bolts. Does anyone know what the proper length of that manifold bolt is and the proper head markings?

Thanks

Jim

Jim------


The bolt was 3/8-16 X 1-1/2" and of material grade GM-280M (SAE grade 5; 3 radial lines on head). It is a trimmed (i.e. non-indented head) and black phosphate finish. Part number was GM #9418968 but it's long-since GM discontinued. Common headmarkings were "M" or "A".

[Gary B.]

Re: A.I.R. Bracket to Intake Manifold Bolt

Jim,

AMK Products sells a repro of that bolt that looks reasonably correct. Here’s an image from their catalog. The S2 finish means it’s black phosphate, so it seems like it should meet your needs. Having said that, the A headmark might not exactly match the GM letter style.

The one downside to buying from AMK is they have a minimum $30 order, plus $10 for shipping. So, you’ll never get away for less than $40.

Gary

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