quote Originally posted by qwikgta: Guru, love the work and I'm sure its worth the work to say you built them from scratch, but do you think that you will gain all that much using the LS7 manis vs. stock LS3 or a set of headers like Archie makes for his swaps. When I had Archie do my install, I had him pass me a pic of the stock mani's vs his headers. I would think the header would offer a few more ponies. BUT again, I do love the work you put in on yours. Rob

I considered alot of exhaust options before settling on the LS7 manifolds.
**LS4's have a complete header/crossover/downpipe setup for the FWD croud (about $700), but I didn't know how it would clear the F40 and I know the cross over pipe would not clear the LS2 intake.
**LS2/LS3 stock manifolds would also work, but I didn't like the idea of them corroding behind the heat shields, plus the heat shields are only on one side.
**Early LS1 Corvette manifolds - double wall stainless for heat and noise suppession... these were strong contenders.
**After market headers... I have had way too many cracked headers with the shorty style on the SBC's... didn't think much about avoiding them entirely.
**Custom long tube headers using a sprint car weld up kit where all the tubes are biased to the front of the engine. Add the LS1 flange, cut to fit and I would have a 3/4 length header... these kits are not sold in stainless, but this still could be an option in the future.
**LS7 factory exhaust manifolds. I am a big fan of GM's durability testing and prefer to use as many GM designed parts as possible. The LS7 manifolds are also quite compact and easily fit the fiero engine bay. The LS7 manifolds are actually hydroformed tubular stainless steel headers and fully incased in another section of stainless steel for noise and heat suppession. They work very, very well and have proven to be worth 10-25 hp compared to LS2 or LS3 manifolds. Long tube headers can out perform them, but I doubt any short runner header will. So for around $100 the LS7 manifolds provide a very durable solution that pasted GM duability tests to perform leak/crack free under 500hp conditions, they are stainless steel so they will retain their good looks, they will put minimal noise/heat put into the engine bay, they are lighter than the LS4 manifolds (before I cut the flange off), and they have been proven to work well... My question is why isn't everyone using them?

Here is a cut away pic to show you what the insides look like:


Now the LS7 manifolds are probably a little big for the a stock 5.3L, but I may choose to upgrade some cubes in the future. For reference the tube cross-sectional area at the port is about 2.37in-sq and 2.12in-sq at the collector with the primaries being about 8" in length on the inboard cylinders and about 10" on the outer ones. The DT headers are 2.40in-sq for their length, but do have primaries that are 1 1/2 to 2x as long.

[This message has been edited by fieroguru (edited 03-07-2011).]

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SSFiero@Aol.com 87 Gt-5spd-62k miles.