Exhaust Manifold Bolts

[JeepJeepster]

I used grade 8 bolts, lots of antiseize, and nord lock wedge locking washers.

[Ristow]

i believe the bolts were hollow so they would stretch more easily upon torque down,which keeps them snug thru the temp swings.


i use plain bolts when the hollow bolts are not useable.


anyone that has fought the older 3/8' bolts into position appreciated the move to the 5/16 bolts.

[babywag]

I have just regular ole bolts on both my GWs.
88 even has headers, no leaks, have stayed tight, etc.
I do recall back in 2005 a couple bolts broke on removal.
The hollow bolts made for super simple removal.

[Rod2]

I replaced my manny bolts with 3/8 stainless steel bolts--not hollow and no problems,

[61Hawk]

I replaced my manny bolts with 3/8 stainless steel bolts--not hollow and no problems,

Aren't stainless steel bolts awful brittle?

[Wagoneer Taylor]

Aren't stainless steel bolts awful brittle?

Not sure about brittle, but stainless bolts are roughly equivalent to Grade 5 bolts as far as strength. Grade 8 is "stronger", I am sure it is fine to use stainless in this application. I am by no means an expert, but I use ALOT of stainless fasteners and material in my work. We use them not so much for the strength but the corrosion and heat resistance, strength just happens to be happy by product. I have found stainless to be more likely to seize or gale during installation, but when removing after a long time or many heat cycles they usually come out just fine. (we use them in heater blocks that got up to about 500 F)

I may have steered us a little off track but I thought this was a cool exercise of thinking about hollowed stainless bolts and how they might hold up to this same situation.

[wiley-moeracing]

Use anti seize when installing stainless steel.

[hojoos]

The space around the bolt allows for thermal expansion of the exhaust manifold. Big chunks of cast iron expand quite a bit when they get as hot as exhaust manifolds do, and the manifolds would crack if they were not allowed to shift and "creep" around the bolts as they expand and contract. The bolt holes in the center of the manifolds are smaller because they are there to hold the center of the manifold in place while the far ends of the manifolds expand and contract. That is why the bolt holes out at the far ends are larger than the bolt holes in the center.