GM Part Number for Exhaust Manifold Bolts

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Schurkey

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Since the original bolt has a flanged head, three or four flat washers on the replacement bolts would likely be all that's needed.

Verify that there's no bolt shank coming through the exhaust manifold, and that you don't have excess thread engagement. Easily measured.

I would be sure to add anti-seize to the bolt threads, and to clean-out the threaded holes in the cylinder head with a thread-restoring (NOT a thread-cutting) tap.

If the manifolds are flat and smooth, and the head surface is flat and smooth, you most-likely don't need a gasket. But none of my Vortec core engines came to me with exhaust manifolds, so I don't know what GM did or didn't do in regards to gaskets. The Vortecs seem to be prone to cracking the iron exhaust manifolds, and the Dorman replacements will not be useable out-of-the-box. Every Dorman exhaust manifold I've ever seen has been warped and with rough machining. I have heard--but not verified--that the Dorman Chinese manifolds are actually better than the Dorman Vietnamese manifolds, which must be truly horrible.
 

Nad_Yvalhosert

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now i'm more confused than before, all the parts listed on rockauto and summit and amazon have a ton of negative comments mentioning that all the sites sell the wrong bolts, needed are 2 1/4" and sold are 2 1/2"

I just replaced my manifolds with shorty headers. The OE manifold is 2" thick and all my bolts had spark plug heat shields installed. (Yes I know they're super thin)
2.25" bolts doesn't leave much thread, and its hard to imagine that there's only a quarter inch of bolt threads hold the manifolds to the heads. Looking at the pic shows a half inch of clean thread. So 1/2" of thread inside the head, plus a 2 inch manifold equals 2.25"?

Has anyone ever checked the depth of the holes?
 

MrPink

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I just tried looking them up and I'm running into the same issue, it's like they were never included in the parts diagrams.

Maybe @MrPink can look them up?
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now i'm more confused than before, all the parts listed on rockauto and summit and amazon have a ton of negative comments mentioning that all the sites sell the wrong bolts, needed are 2 1/4" and sold are 2 1/2"
They are 2 1/8" not 2 1/4"
 

wezmykat

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great, one more wrong size, here's the plan then, I will go to Home Depot or Grainger Industrial or some other place where I can find some quality bolts, which likely will be very hard/impossible to find flanged, the extra washer or two sounds like a good solution, I will put the bolts side by side and if they are still too long I will simply cut a piece off with cutting wheel and then they should fit just fine.
Remove all old bolts, install new gaskets and put new ones with the old OEM manifolds back on (even though cracked here and there) + new donuts and exhaust flange studs and nuts

While writing this was looking and found yet another size, according to Fel-Pro, the correct size is 2 11/32" (part number FEL-PRO ES75119 / 1991-2002 GM 5.0L/5.7L) and their stuff looks decent, a lot more more expensive though, maybe worth it? since those cheap bolts will likely snap a few miles down the road from the extreme temperature changes...
 

east302

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In an older diagam the exhaust stud # 14029009, and the bolts are # 09442012.
That’s what I see as well for the L31.
3/8-16x2.25

On mine (98 350) depth is about 0.890”
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Papablunt

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great, one more wrong size, here's the plan then, I will go to Home Depot or Grainger Industrial or some other place where I can find some quality bolts, which likely will be very hard/impossible to find flanged, the extra washer or two sounds like a good solution, I will put the bolts side by side and if they are still too long I will simply cut a piece off with cutting wheel and then they should fit just fine.
Remove all old bolts, install new gaskets and put new ones with the old OEM manifolds back on (even though cracked here and there) + new donuts and exhaust flange studs and nuts

While writing this was looking and found yet another size, according to Fel-Pro, the correct size is 2 11/32" (part number FEL-PRO ES75119 / 1991-2002 GM 5.0L/5.7L) and their stuff looks decent, a lot more more expensive though, maybe worth it? since those cheap bolts will likely snap a few miles down the road from the extreme temperature changes...

How did everything work out?
 

1998_K1500_Sub

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I will go to Home Depot or Grainger Industrial or some other place where I can find some quality bolts,

Fastenal too… my goto anyway, they’re close by. The seem to have stores within easy reach, coast to coast.

I used them most recently to get a 7/16" fine thread, 3.25" long grade 8 for a SBC crank pulley.
 
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