Anybody know how much horsepower I should gain by just adding headers? I have a 2001 GT with automatic trans and stock exhaust, except for the addition of 40 series flowmasters. I have a friend who thinks he can get me some long tube headers dirt cheap, and I want to know how much power increase I can expect and what kind of et improvements I might get.

By the way, best time I've run is a 14.93 @ 94mph

Any comments would be appreciated!

 

You would probably get around 15-20 hp/tq. The longtubes help fatten up the torque curve in lower rpms as well. You'd need to replace your stock H-pipe being it won't mate up to long tubes. Most longtube headers have a matching H or X pipe to go with them. Unless your mechanically savvy, let a shop install them. Its not easy or fun.

 

I would guess closer to 20hp and x2 on the install its about a 6 hr install from what I have heard

 

I believe on a stock mod-motor car the difference is not much. On a 4-valve or a 5.0, yes...

It'd do the rest of the exhaust (midpipe and catback, NOT just mufflers) too. Reason I say "NOT just mufflers" is because mufflers have virtually NO effect on performance, just sound.

A cold-air intake, tune, and UD pulleys wouldn't hurt either, and you can do the first two yourself in a short amount of time.

 

To get the best performance possible, do the entire exhaust. If you're getting LTs, you'll have to replace the mid-pipe anyway, so you might as well do the cat back as well. You should be able to do the mid-pipe and the catback yourself (better to have a friend help, as it can take two people about 6 hours for both) without much trouble, it just takes awhile to do.

A CAI, tune, and pully swap will probably boost you to around 14 flat, depending on the driver.

With a CAI and SLP Catback, I now run about 14.5, but I'm an auto vert, uphill battle for me!

Mufflers themselves do nothing but change the sound. It's almost a pointless mod unless you don't care about performance.

 

you're kidding about mufflers making no difference right? factory exhaust is designed to accomodate noise levels first performance second, or not at all...

 

Yep, but he has FLOWMASTERS.

Also, if the factory thinks quiet first, how come axle-backs on an S197 has little or no performance gain? Same goes for C5 Vettes, too.

 

A muffler swap on a friend's 2006 GT made a total of 2HP and decreased TQ by 3. And it was Flows as well. Since then, he returned the mufflers and got a full SLP catback and is much faster. He hasn't dynoed yet, but we think it's around 15-20HP.

Trash the muffler swap and go with a cat-back.

 

Noticed your future mod list included X-pipe, tune, and plenum. These things really helped my 01 auto at the track. I managed a 13.7 on original tires with mods in my sig. minus the plenum.

 

shorty headers you will not see much gain. but have heard the 2v engines respond well to long tubes.

 

More like H-Pipe. I'm not too fond of the X-Pipe's sound. Also, I just found out that my sub-division has a sound ordinance, and any louder my car will be in violation. I hate homerowner's associations. Have to pay money just to be hasseled...

 

just drive really slow while in the neighborhood

 

Just find who run's the thing, wait outside their house at night and jump them.

It's about as fair.

 

how much of a difference will headers make on a 5.0 with shorties compared to LTs. with a cam and head upgrade?

 

It's about 5 different people that come up with random rules to make my life hell. Everything I want to do, built a garage myself, park my car on my front yard while I'm washing her (to show her off. ), work on my exhaust at 3am and starting her with no midpipe.

I do enjoy going to the lake and flooring her, scares the old people that's fishing!

 

Shorties? 5-10rwhp? Long tubes? 15-25rwhp?

At minimum, LTs are making at nearly twice the max gains for shorties, up to 4 or 5 times as much.

 

That's an awesome time for an auto. I'm running 14.1s with everything now on my auto on street tires. There was a guy at the track last season with an 02 auto running 13.5s and all he had were headers, drag radials, and 4.10s.

Strange how each car reacts differently to mods.

 

4.10s are one of the best mods you can do if you're planning on racing a lot. Even daily driving it's a good mod. Just eats your gas up alittle faster.

 

long tubes with an o/r x can expect around 25hp/tq. over stock with a good tune. with cats between 15-20.

 

What elevation are you running at out there?? Just above 400' here.