Some of you have seen this on LS1Tech.com, but we don't need headers to get 400 rwhp. Stock '99 Z28 exhaust manifolds were used with these parts: '99 LS1 engine, 243 heads, COMP 26918 springs, LS6 intake, EPS cam, 218/230-115 at 111, .595/.600 and a stock (SS?) airbox (which was tested as giving 7 kpa of vac at WOT on this combo) The result was 403 rwhp at 5900 rpm, with 392 rwtq. it was said to pull well to 6600 rpm with none of the sewing machine noise like most other LSx cams. I'm not pushing this cam, but it's $390 from Geoff at Engine Power Systems, phone (225)751-8500. I thought this was good news and maybe someone else would also find it interesting. I can only assume these results were with a manual transmission and synthetic lubes in the trans and axle. The baseline was 332 rwhp @ 5400 rpm and 347 rwtq @ 4300 rpm.

think of how much more it would be if you actually had a balanced combo though.

You missed the point. You can find thousands of better results with headers all over LS1Tech.com, but some of us can't use the headers in our third gens because of emissions inspections. Others of us are building Fieros, for which these '98-'02 Z28 exhaust manifolds are the best fit, and NO headers exist. For these people, (and I fit both categories) this combo is cause for celebration. BTW, these exhaust manifolds are also popular for those putting LSx engines into little S-10 chevy mini pickup trucks. Which category I also fit into.

I fit into the category. Not 100% sure if I would have a problem with emissions if I used the hawks headers, but the cost is just too much for me at this time. '02 SS Manifolds for me.

similar combo with stock manifolds/exhaust with AFR heads and cheatr cam which was something similar to that above cam makes 400whp

Not sure how stock 243 heads are supporting that. they ported 243's?

I think it's pretty cool, personally. Seems like it's a testament to two things -

1 - the efficiency of the engine design, &
2 - a pretty darn good exhaust manifold design.

From my own perspective, I finally got freakin' sick & tired of how long my project's taking me, so I bought a set of '02 exhaust manifolds, just to try & get the car on the road, instead of waiting for how long it takes me to build headers. And since my engine's rated at 403 hp from the factory, it gives me hope that the manifolds won't choke it too badly...

IIRC the T-Rex cam was designed to extract the most power possible though a stock LS1 ( meaning no headers, porting, etc only cat back and those kind of bolt ons ) Its a knarly cam but if you want big power on the cheap dump a T-Rex in a stock LS1 with a 150 shot and run 10's

I thought there were carb approved shorty headers, at least for gen 1 blocks. Are there none for ls engines? Seems like there would be too much of a market for those to have them not exist.

This is something we've all been searching for, for a few years now. At present, you have 4 choices: (1) stock exhaust manifolds, with or without cats, on your LSx third gen(2) Hawks headers and no cats possible on your LSx third gen (3) custom headers you make yourself, with or without cats, on your LSx third gen (4) don't put an LSx in your third gen.

theres alot of power being left on the table with that motor by not running headers. i bet that motor would net an additional 20-30hp with a nice set of LT's

Does anyone know if the fbody's LSx stock manifolds will fit the gen 3 5.3?

I would think they would fit just fine on the 5.3 since its the same family basically.

This method works best. Buy a set of big block headers for thirdgens and cut the flanges for LS1 flange. Or buy a set of small block headers and cut the tubes/flanges for LS1 flange. My buddy did this to his el camino 6.0liter swap. big block headers just cut and refinished at the flange to mate to the LS1 head. Not to hard to do if you can cut/tack weld up some pipes.

You also missed the point. Try reading the entire thread.

Yes, they fit perfectly. I've done it.

This cam would not be one to use if you're going to use headers. So we should never know what this combo would do with headers.

Taking the design of that cam into consideration, being that it is aimed for stock blocks, what kind of gain *should* you see on a stock block with a set of longtubes as opposed to a stock block with the T-Rex?

As in cam versus headers?

Ya, I understand why some people doing LS swaps with manifolds, like in Fieros and such, but for the majority of us HERE anyways, it is important to consider the cost of the T-rex cam opposed to the cost of longtubes, while the cam will limit the potential of the motor in the long run with more mods, and the longtubes will cost more up front but open up the potential for the block much more.

So in that argement, how much power will that cam net you as opposed to a stock block with longtubes?

Good question and to that I have no idea but the general consensus that most seem to agree on is a set of LT's on an LS1 is worth 20-30 rwhp on a stockish engine. Meaning little or no cam but supporting bolt ons etc as in catback and whatnot because not many ( if any? ) are running LT's though a stock exhaust.

The T-Rex may add about the same but its such a nasty cam I'd much rather have the LT's personally. Combine them with a small 224 range came and tune you can easily have an 11 second daily driver thats efficient and fun to drive without suffering drive ability.

FWIW I've also come to appreciate the dyno vs the performance factor much more than I used to. Its not always the high peak rwhp LS cars that run fast at the track.

I totally agree with CAM's last post.

Edelbrock shorties fit, work a bit better than manifolds, look better, and are cheap. They also have a CARB number.

Do you have a picture of those Edelbrock shorties installed I would be intersted to see that. As I am trying to decide what exhaust to put on my swap.

They are a stock replacement for manifolds, a little tight on the pass. side, but they are easy to install, just not much wiggle room. Stainless tubing, ceramic coated.

Looks good what kind of power difference do you think there is between those and say Hawks Long Tubes? Have you had your car on the dyno, if so what kind or numbers was it putting out with that combo? I currently am just running stock manifolds and a crappy Y-pipe setup. But I am getting ready to build a double hump crossmember, install some headers, and build a better flowing y-pipe. I am just trying to figure out all my options. Obviously I want to make the most power i can for the best money investment.

The general consensus seems to be that there's really not a significant difference between stock F-body manifolds and shorty headers. It takes long-tubes (not necessarily Hawk's/SW) to wake up an LS-series engine.

I saw a test between the factory Corvette exhaust manifolds and aftermarket long tubes. Their was not much to be gained by going to long tubes. I would look into the Corvette exhaust manifolds and see if they will fit. They are pretty darn good.

Hey guys, this is great news. I don't have a 3rd gen, but I do have a 93 Mazda Rx-7 that is hosting an LS1 from a 2002 Camaro Z28. For this application, the stock manifolds fit pretty well, and so do the cats (although it looks like I may have to run two passenger side cats since the pass side cat is smaller). I'm one of those guys who need to keep stock manis and cats in order to comply with emissions regulations. I've been looking for info like this. Would like to see more dyno charts... when I get my motor broken in I will have it dyno tuned. Looking for 350-400 hp @ the wheels, and still be able to smog it.

Here's the setup:

Exhaust: stock Z28 manifolds & cats, custom piping to 3" ID muffler
Cam: 224/228 114 LSA 0.568/0.588 +2 advance
Heads: TSP Stage 2.5 5.3L heads
Trans: stock T-56
Rear end: stock Mazda 4.10

The TREX was designed for cars with all supporting bolt ons. Without a set of headers the bottom end will suffer considerably as compared to a cheatr cammed car. Pat Guerra designed both of those cheatr systems, but with Geoffs new lobes its now possible with a set of budget heads that can usually be had for less then 500$ vs. the 2k+ AFRS. FWIW I had Pat G custom spec a cam for my 5.3 with stock manifolds with a 325-350 RWHP goal stated. Oddly it looks very very close to that one save for a few degrees off the lsa.

If most of us could afford a set of headers, or have the equipment available to fabricate them im sure it would be a different story.

you can pretty much use any of the carb legal shorty headers from a fourth gen. they will help. i am going to be using doug thorley 5th gen shorty headers. .

EPS cams have been showing impressive results. Very impressive

FWIW I too am running a PatG custom spec EPS cam in my VVT equipped L92 6.2L build whoot!

I've got a question that some one might have info on. Since we are debating the necessity of LT headers ( a la hawks), would they be absolutely necessary on a cammed car? I have a LQ4, with 241 heads, a Tv2 cam (113+3 232/234 .598/.595Z). I am pretty stretched thin on my budget, thanks to being ripped off and may not be able to afford headers.

If I could get away with manifolds that would be far more preferable, as the fit, clearance, and routing is all much better. Would that be a viable option or will I be looking at losing ~40rwhp with manifolds vs headers?

If no one has seen/tried this, I will post up my results in comparison to a local guy who has the same combo, but with LT headers.

You will likely be giving up a considerable amount of power, why dont you sell that cam on ls1 tech and put the funds towards one of these cheatr cams from Geoff. According to Pat G, these will idle like stocl in 6.0 and above engines and produce a nice solid torque number.

wow did you say 241 heads. i thought those were stock ls1 heads. you are giving up power with those. like said above they are going to be your achille's heel. you should be looking more toward the torquer cams.

Actually 241 heads have made great power on stock ls1's with cam only. It's also a good way to bump compression on a 6.0 engine. The torques cams are only going to benefit him with proper exhaust, I.e. Headers. He cam actually make better power with a cheater cam and manifolds then the torques cam and manifolds based solely on the new lobes from Geoff. IMO that are that good.

They aren't stock 241 heads. They are shaved, ported, and have oversized manley stainless valves. I am also running a Torquer V2/XER281HR cam (232/234 595/598 113+3).