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You are watching: Chevy 5.7 exhaust manifold bolt size


I am looking to replace my exhaust manifold-to-head mounting bolts with grade 8 hardware. Engine is a 1990 TBI 350 with the stock serpentine setup and manifolds. I"m helping a friend get this engine running, and we basically started with a box of parts so we"re not entirely sure what is what.What I need to know is the specs of the bolts themselves. I know they are 3/8" but length? Also, I believe there is a stud in each manifold, possibly for the accessories. Size of those?Thanks,Brendan
I am looking to replace my exhaust manifold-to-head mounting bolts with grade 8 hardware. Engine is a 1990 TBI 350 with the stock serpentine setup and manifolds. I"m helping a friend get this engine running, and we basically started with a box of parts so we"re not entirely sure what is what.What I need to know is the specs of the bolts themselves. I know they are 3/8" but length? Also, I believe there is a stud in each manifold, possibly for the accessories. Size of those?Thanks,Brendan
3/4 inch or 20 mm depending. Why grade 8? These things only spec to 25 foot pounds, not exactly a challenge for a 3/8s bolt. Plus they rust, get some stainless steel and make the next removal a lot easier, same goes with the bolts or studs that connect the head pipes to the manifold, stainless, so you can get it apart next year.Bogie
Why grade 8?
These things only spec to 25 foot pounds, not exactly a challenge for a 3/8s bolt. Plus they rust, get some stainless steel and make the next removal a lot easier, same goes with the bolts or studs that connect the head pipes to the manifold, stainless, so you can get it apart next year.

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Ayuh,... The SSteel idea is a Good 1,...I"ve done a few with steel studs,+ Brass nuts.... Just because of the Rust factor...
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