Suggestions for exhaust

[MontanaH3Guy]

I'm doing an LS swap in my 06 H3 and I'm looking for suggestions on exhaust manifolds or headers, especially the drivers "left" side. Does anyone have any ideas where to find a manifold that will fit with the 5.3 LS. The one I have drops straight into the frame.

 

[amrg]

One guy said he used doug thorley headers for a 2009 V8 chevy colorado, some hammer work and it fit. Now did he post pics? No. Do I believe him?
There are 2 guys right now using bbk shorty headers but there are also alot of work and they are in no way a ditect fit. The thorley ones may or may not be a better option.
So, Apart from alpha manifolds, pick your poison.

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[jimmy p]

Just go with h3 alpha exhaust manifolds, cheap and they fit. There is very little if any benefit to short headers.

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[Gpcalero]

I am using some ceramic coated JBA headers. The passenger side exit is aimed nicely parallel to the frame. The driver side is a little bit more tight but it fits on my vehicle without any modifications to the header or surrounding parts on my truck (besides the receiving stock exhaust). I am in the middle of a swap myself and the stock exhaust will be a little bit off on the passenger side but you should be able to fabricate the little misalignment there. The driver side however is quite a bit off, and it does get close to the frame but you can make it work.

Here is the passenger side showing how nicely it falls into place. And then below, my driver side. Don’t pay attention to my booger welds, this is just a temporary set up to finish my swap before I have an actual exhaust shop weld me in a full system lol. I am by no means a good welder! :giggle:








Jimmy P is right, stock manifolds are cheap. Will probably be a good idea to go with those since they perform well already. But shorties WILL give you a bit more performance. ~5 hp/5 tq average gain with a shorty type header over an OEM corvette iron shorty on a 5.3. More gains with a larger engine and/or boost but for how much horsepower you get for $500 or more, it definitely isn’t worth the cost over Alpha manifolds to me.

Hope this helps!

 

[MontanaH3Guy]

Thanks for the suggestions! I think I found the left side OEM manifold on Summit as well as GM parts supply. Neither have a picture of what I'd be getting but both say they're in stock. We'll see who can get it to me the fastest.

 

[amrg]

Double check before you purchase. When my buddy ordered gis it took months to be shipped although it was in stock initially

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[Sbc350_h3]

I'm running a 4 inch straight exhaust with stock sbc manifolds on my h3 with a 5.7 in it.

 

[Gpcalero]

I'm running a 4 inch straight exhaust with stock sbc manifolds on my h3 with a 5.7 in it.

4" exhaust is pretty big, and overkill in my opinion.

Any pics?

 

[Sbc350_h3]

4" exhaust is pretty big, and overkill in my opinion.

Any pics?

I have vids on youtube. Just search sbc h3 mine is the white one with sbc swap I have a vid of it running right after I did the exhaust.

 

[zebra]

4" exhaust is pretty big, and overkill in my opinion.

Any pics?

a 4" single for a 350... not necessarily too big if it's a built motor. would 3" have better scavenging velocity? probably


but like Gpcalero said on an LS swap, the cost:benefit of shorties (that may or may not actually fit right) vs stock alpha manifolds - the OEMs win.

 

[amrg]

A 4" pipe is good up to 450 hp but dual 2.5" will be better to 50php and easier to build

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[Gpcalero]

a 4" single for a 350... not necessarily too big if it's a built motor. would 3" have better scavenging velocity? probably


but like Gpcalero said on an LS swap, the cost:benefit of shorties (that may or may not actually fit right) vs stock alpha manifolds - the OEMs win.

Ah, if it was a 4" single, then that would be different. I was thinking he meant dual 4" exhaust (which again, would be overkill on these). For reference, I have dual 3" pipes dumping just past my transmission on my 1000hp mustang.