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Exhaust Manifold Bolts

Exhaust Manifold Bolts

Exhaust Manifold Bolts

I am looking for a different bolt material to secure a guard to an cast iron exhaust manifold. The current grade 8 steel fasteners snap off when you turn them out, or will loosen and fall out. Manifold temps are about 600degF. Any recomendations for something better?

I see 309/310 as well as 316/317 Stainless Steel being recommend.

RE: Exhaust Manifold Bolts

Are your failing fasteners plated with zinc or otherwise supplied 'bright'?

ISTR that zinc embrittles steel of all kinds at the high temperatures to be expected in exhaust manifolds and abused clutches.

Instead, I use uncoated/black/plain fasteners and completely cover them with Never-Seez.

Mike Halloran
Pembroke Pines, FL, USA

RE: Exhaust Manifold Bolts

Use stainless steel bolts or studs.

RE: Exhaust Manifold Bolts

Is this a non-stock application?

Why were the grade 8 fasteners used?

RE: Exhaust Manifold Bolts

The orginal bolts that failed are yellow zinc. No reason grade 8 was used other than that was what we used across the board.

This is a stock application. Its a industrial diesel engine on a drill rig.

RE: Exhaust Manifold Bolts

" Its a industrial diesel engine on a drill rig."


Did the yellow zinc stock bolts fail the same way as the gradeeightz?

Is there room to use longer bolts with spacers so clamp length to diameter gets up around 8 to 1 ?

RE: Exhaust Manifold Bolts

Moose- This machine is land based in a very dry climate.The bolts we used are grade 8 with yellow zinc coating.
I have used 3.5" long spacers on a 5/16" bolt. That give you an L/D ratio of 11.2:1.

Thanks Tbuelna.

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