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I know this has been asked before, but has anyone actually done this?
More importantly, does it yield any benefits?
I race in a class that requires OEM manifolds and from what I have seen, the LS7 and maybe the LS9 exhaust manifolds flow better than the Gen III manifolds.
I know the port size is different and bigger on the LS7, so it's not as bad as going the other way, but probably not ideal?
You would definitely gain power with the LS7 manifolds, as far as them having the D ports it won't matter as long as you use the LS7 D Port gaskets as well, the main problem is you will also need the connection pipes too which are very hard to find with out buying both LS7 Catalytic converters which are $$$$...the LS7 manifolds have an oval shape where the exhaust exits the manifold, much different than your factory LS6 manifolds...see pics below
Thanks for that!
Of course the gaskets make sense.
Are the LS9 manifolds the same as LS7?
They seem to be a lot cheaper to find than the LS7 ones.
As for cats, we won't run them.
What downpipe is that? Is that a factory piece, just cut up?
David
Originally Posted by 01FormulaTA
You would definitely gain power with the LS7 manifolds, as far as them having the D ports it won't matter as long as you use the LS7 D Port gaskets as well, the main problem is you will also need the connection pipes too which are very hard to find with out buying both LS7 Catalytic converters which are $$$$...the LS7 manifolds have an oval shape where the exhaust exits the manifold, much different than your factory LS6 manifolds...see pics below
LS7 and LS9 exhaust manifolds are the same, and yes those connection pipes were stock pipes cutoff at the catalytic converter....I was saying to obtain those connection pipes you will need to purchase the cats, not run them...there are 2 cat connection pipes that you will need to buy and then cut off the pipe right before the cat (see pic below)
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LS7 Exhaust Manifold on LS6 
