Porting the SR20DET exhaust manifold

[S13 King]

I did search first...

I'm replacing the gaskets on my manifold to turbo and manifold to block and my friends and i were tossing the idea around of porting out my exhaust manifold. Is there a big gain from this and if so how do you go about doing it?

[180fan]

if you're looking for big gains, don't bother with a port and polish on your exhaust manifold. get the head ported and polished instead.

[S13 King]

yea we passed on doing that, just seeming like more time consumming.

[SRdave240]

When I had mine off to fix my exhaust leak I gave it a little cleaning of the casting lines and smoothed up the ports a little bit. It didn't really seem to make much of a difference. I took off very little material though.

I wouldn't bother. If you are putting down less than 300whp it doesn't really help. If you are putting down more than that, even a cheap tubular manifold will give you MUCH better gains.

[lok]

When I had mine off to fix my exhaust leak I gave it a little cleaning of the casting lines and smoothed up the ports a little bit. It didn't really seem to make much of a difference. I took off very little material though.

I wouldn't bother. If you are putting down less than 300whp it doesn't really help. If you are putting down more than that, even a cheap tubular manifold will give you MUCH better gains.

oh that is why you have the 5500 speed cut. should have left it dirty.

i also opted not to port mine while fixing the leak.

[S13 King]

well what is a good reliable exhaust manifold?I know that i will either stay with the T25 or go to a T28. So it would have to have the flange for that.

Suggestions?

[drumma022]

Every stainless manifold that is out there, I have seen crack or heard about cracking ... EXCEPT for the Full Race manifold, but that is a top mount T3 manifold.

I have considered sending out my manifold to have it extrude honed, but I don't have the time to pull my manifold off.

[VitaminT]

How much does the extrude honing cost? Who can do it? I have a spare mani that is jethot coated that I wouldn't mind have that done to.

[180crafter]

Extrude honed is very pricey. I have looked into it, and just plan on porting it myself when my ss mani breaks. It shouldnt since I reinforced it like carzy, but you never know.

Does anyone know whrer they usually break? I would like to keep an eye on it b4 it melts my engine bay.

[VitaminT]

I think it is where the 4 -1 collector is. If you are worried about it just put a flexpipe in your downpipe and you shouldn't have any problems at all. The reason they crack is because the are not flex points from the head all the way to the muffler tip. The exhaust swinging on its hangers acts like a "breaker" bar and cracks the mani.

I guess that is my opinion at least.

[nismostate]

DSM guys port their exhaust mani and supposedly provide a better flow and a little gain. they port the elbow also. we did it on his with a die grinder and a carbide bit. it's a pretty easy DIY. i might just try it whenever i do take it off. by the way, why don't companies make a freaking straight/flex pipe? that is such an easy thing to create. and some might think it's a cat. :pface

edit: some have talked about porting the o2 housing. http://www.nissaninfiniticlub....rting

IMO, get a die grinder and a carbide bit and it will take off metal like it's nothing. get the right bit and it'll be easy. I got the 90 psi die grinder from harborfreight.com. best 15$ tool!

[S13 King]

well if you use NISMO exhaust hanger bushings they prevent the exhaust from swinging.

[nismostate]

exhaust swinging is not the problem. if your car is low and it bottoms out on the turbo back piping, it will crack the manifold.

[msaskin]

The exhaust will still swing. Short of welding the entire exhaust setup to the frame at multiple points you aren't going to keep it from moving around.

The best (and safest) option is still to have a flex section welded onto your downpipe.

~matt

[S13 King]

since i'm new to all thisthe Flex section is? Like a peice of piping that absorbs shocks and hits?

[SRdave240]

The exhaust will still swing. Short of welding the entire exhaust setup to the frame at multiple points you aren't going to keep it from moving around.

Oh, and don't forget about welding your engine and transmission mounts too! LOL:D

yeah, like Mike said, the exhaust is gunna move a little. Flex section is the best idea IMHO.

[dj_lennon_franz]

and this is why i made some cheezy exhaust holders outta sheet metal for the bottom of my car

really easy to do too...took all of 15 min