Seems everybody has a routine around here. Intake and headers before moving onto internals, and I know all the reasons why.

Still, with my *** living in California, my visual modifications options are limited. I'm lucky enough to not have to do bi-yearly smog tests due to my zip code, but I am still at risk for a visual roadside test if a police officer feels like it.

I think I would be able to get away with running a good sized cam since I have no plans to change my SLP DD/cutout combo. On the street, the quiet exhaust should do a decent enough job of hiding the lope, and of course no one would be able to tell with the hood popped.

I know that the gains from headers is incremental, whereas the amount you free up increases when you throw more horsepower at it, but if I was to get a cam that put out about 400 rmhp on a full bolt on car, how much would I lose by sticking with the stock manifolds?

 

I'd imagine at least 20hp. Look for a cam like the CheaTR that is designed to be used with manifolds. OR get out of that environazi state.

 

I think that's a damn good question, and I'd love to know as well!!

Unfortunately, you're right, "everybody" goes the other way ... headers first, or at the same time at least (or so it seems, for the most part). But I'm not convinced there's not more power to be found by simply adding a camshaft to the LS1. I'm no cam "expert", but my guess is that you wouldn't want something that's designed to make power at extremely high RPM's ... you'd probably want to look at a low-mid range cam . Considering you've got a cut-out though, that's going to compensate for your "stuffy" exhaust . So, you could probably get away with a decent camshaft, and have respectable power and efficiency with the cut-out open?

If you don't mind being a bit of a "pioneer", you can experiment a little and let us know how it works out???

 

A cam like the TR Cheater cam will get you very close to the 400whp mark with stock manifolds, thats what they designed it for. And it sounds like stock too. Might be worth you looking into. My FLP LT's gave my car an extra 18rwhp and 20rwtq.......but that was before the cam with no tune.....sorry I can't give you the answer you are looking for...

 

Thanks for the info on the stealthy cams. From what I've been reading, it seems like these would put out more power since they were made for stock exhaust then a more agressive cam would make trying to push through manifolds.

At least I think.

Thunder Racing says it only puts out around 390 at the wheels with their cam and heads package, but threads on MBs show it putting out around those number with cam only. I'll have to call them. I'm also going to look up MTI's Stealth and Stealth II.

 

The main thing they look for and the main thing effecting emissions efficiency, is the location of the cats. MOst LT set ups are illegal because you have moved the stock location of the cat converters. If you can get a set of shorties and maybe, flange mount the cats directly to the headers, they will heat up easier.

I don't really have to worry about emissions here in NM, but if I were to move back to my legal residence of CT, I'd prolly fail..... By then the car will NOT be street legal anyway.

 

yeah, I remember hearing about some set of LT1 long tubes that were smog legal because they wrapped all around the engine bay, therefore not moving the cats. Never made production though. Thing is, you could maybe fool an officer by showing them that you still have cats if you got a catted y, but the shape of the LTs would tip your hat right away. At least I wouln't get the $1000 fine for not having cats though. :eek

From everything I've read, the stock f-body manifolds flow as well as the shorties, so there's no real hp to be gained, at least not worth the price.

 

Just cut the ypipe to fit the cat without moving it back. And your crazy if you think that the stock manifolds flow anywhere near what even a shorty header does.

 

You're thinking of your lt1 single cat exhaust. LS1s have dual cats coming right off the manifolds. What you are describing won't work.

Also, do a search on shorties for the ls1. Everything I've read has pointed to a 5 hp gain at most. Like I said, not worth the money.

 

Yeah, LS1 manifolds, esp. '00 - '02 are actually pretty "decent" for a cast iron, FACTORY manifold .

..... albeit, they're no long-tube!!

 

Stock manifolds on a 2000 or newer work very well. They work so well on a stock internal motor that shorties show almost no gains.

BUT when going to a cam or heads/cam the shorties will definitly help and they are CARB approved emissions legal so no worries there. BBK and Hooker make some and there may be others out there.

Go shorties, high flow cats, and aftermarket y-pipe. That will get you the most legal hp.

 

On a STOCK motor true.

 

Like said before: It'll hold you back quite a bit no matter what cam you go with. It' has pretty much become the norm seeing a stock-motored LS1 with bolt-ons picking up 20+ rwhp and torque with longtubes.

Mike

 

The thing to remember about the stock cast iron manifolds vs. the LT or Mid headers is...

On headers, it gives each cyl it's own runner, and each runner is the same length... That gives equal backpressure/flow across the board.

On a stock manifold, each cyl feeds to a 'log' (on some manifolds). Therefor, each cyl has to fight with the others backpressure which effects the flow and efficiency of trying to exhaust spent gasses. Some spent gasses might be retained because of sed backpressure, also effecting the oxygen content of the proceeding intake/fuel charge.

With all that said, add a cam into the mix with lets say a 114 LSA and long duration. The valve overlap will be greater (both valves open at the same time, during the transition from exhaust to intake.) Now, add a decent ammount of back pressure..... How efficient do you think it will be?? it might be Ok if you had a 115 LSA (basically stock) In that case, you mind as well just add a set of longer ratio roller rockers, which can also be used for a future cam swap.

It's up to you. It's your money. I don't think it will be as efficient, compared to a better flowing exhasut. But it's Cali too..

 

The '01-'02 manifolds work reasonably well up to ~375-400rwhp. The earlier ones do not work nearly as well.