3100 exhaust manifolds on 3500 heads

[Chris88CL]

We've seen the pictures of the headgaskets being compared. But now I need to know if my stock 3100 exhaust manifolds will bolt up and work (just temporarily) to my 3500 top end.

I want to get the top end installed this weekend but I dont have enough time to fab up my headers. Plus the collectors wont be here for a few weeks.

Ive seem comparisons by Whitelightning of the Gen II manifolds with the 3500 exhaust manifold gaskets, but I havent seen any 3100 comparisons.

If I HAVE to, I can install my 3400 manifolds and weld in that downpipe, but I'd prefer to just do all my exhaust fab at once in a few weeks.

It doesnt have to be a perfect fit, just as long as they bolt up and cover the ports in the head without too much overlap I'll be happy.

[MidnightriderZ24]

u can get wrap around style that work perfect with the 3500 heads. 05 3400s have the same exhaust manifold style and previous years, but have a 3500 port on the manifolds

[Chris88CL]

Yeah im not interested in what I can get tho, Im interested in using what I already have so I can get the top end installed this weekend.

Anyone know if the 3100 manifolds will work? I'd rather not have to pull one off my current engine to mock up, but I will if I have to.

[SappySE107]

It will bolt up but the port is just a little smaller than the 3500 ports. If you can grind them on the sides (floor and roof look ok eyeballing it but you could touch them a little), you should be just fine to use the stock manifolds.

[Chris88CL]

Awesome, thanks for the help guys.

Ordered the gasket kit this morning ($242 later, damn you GM!). Should have everything in by saturday evening or sunday at the latest.

[Superdave]

Yep, they'll fit fine