EXHAUST MANIFOLD BOLT FAILURE ON CHEVY 6.0L ls ENGINE

[aL m.]

DOES SOMEONE KNOW THE BOLT SIZE AND REASON FOR THE BOLT FAILURES ON THE 6.0 LS EXHAUST MANIFOLD BOLTS?

[CamGTP]

A million heat cycles and not a high enough quality bolt material is why they break. The exhaust manifolds do a lot of flexing from heating up and cooling back down and they heat up and cool down at different rates compared to the aluminum cylinder head they are bolted too.

 

Any auto parts store sells new bolt kits to help fix this problem.

 

M8 x 1.25 thread if I remember right.

[Formulabruce]

When replacing, I use "Copper" Never size to add a 3rd dissimilar metal between the threads.

I get no corrosion of any type.

 There are brackets to hold the manifold tight on the DS rear if you want a quick fix, but it bolts to the back of the head.

[C/K Man]

Common on any aluminum head engine with iron exhaust manifolds.  Fixed dozens on various LS engines over the years, and it's MUCH easier than doing the same repair on a Mod or 6.2L Ford (they do it too).