3400 Rear Manifold Outlet Small

[IsaacHayes]

Strange, the 3400 manifold I have was ported out a lot and matches the exit size, while my 3100 one looks like the picture above, and can not be ported any larger.

Regardless, the 3400 rear is better because it has short runners instead of being just a log.

[bszopi]

i could but i heard sticking the stock 3100 manifold on the 3400 heads defeats the purpose of the swap

Where did you hear that? I don't think I've ever seen that said on here. Granted, all stock manifolds suck, and the 3400 one may be slightly better, but they still suck. The only difference between the 3100 and 3400 heads is a larger intake valve, so I don't see that being a reason for your statement either. Perhaps I am mssing something...

[robertisaar]

now you see why you can gain so much power from a better downpipe/good headers. i'm guessing this is GM's prefered method of power limiting.

[90GTZHO]

i could but i heard sticking the stock 3100 manifold on the 3400 heads defeats the purpose of the swap

[Weatheralls Auto]

Well could you not just use the Manifolds that you had in the car in the first place?

[90GTZHO]

I have been searching around the site and a couple other places with no luck of finding an answer to that im searching for.

I recently bought a 99 GA SE 3400 to which i planned to drop into my wifes new 95 GAGT. After discovering that the yard sold me a bad motor with a snapped cam, i went looking elsewhere for a motor. I found a zero mile 2000 3400 for a real good deal that had been rebuilt by a local chevy dealer (aside from heads and block, everything was new ).

Anyways, looking at the rear exhaust manifold, i noticed the outlet on the 99 3400 rear exhaust manifold was really tiny. And upon looking at the 95 3100 rear manifold it looks to have a bigger opening for the downpipe.

My question is, is there something that can be done about the outlet on the 99 3400 rear exhaust manifold, its so smalli dont see how it flows better than the 3100.

Can someone help me out? I dont have a pic of the 3100 manifold, but its a center exit pipe like the 3400 one is. Heres a pic of the 3400 rear manifold downpipe outlet.



I cant port the the hell out of that cause it will burn thru the walls. Is there a better alternative to porting this, like a better manifold to use?

Sorry so long, and thanks.