Long Tube Headers

[Nick S]

I have been looking at having long tube headers installed on my LT4 Corvette. If I do, I am going to purchase the Exotic Muscle 1 3/4" ceramic coated full length headers and Random Technology high flow catalytic converters. I plan to run this into a Corsa cat-back exhaust that is already on the car.

My question is, how much horsepower can be gained by doing this to an otherwise stock motor? The car dynoed at 290 hp on a Mustang Dyno with the Corsa exhaust installed. I am afraid that this modification may not yield much of a horsepower gain (more than 10 hp) unless I make changes to the camshaft, heads, or intake.

Thank you for any replies.

Nick

 

[Hrtbeat1]

Don't be surprised if you don't see ANY gain, and most likely a loss. I did until I re-tuned the PCM. Mine stock dynoed at 308 rwhp, after putting the headers on I re-dynoed at 298 rwhp. The car was really rich, on second set of pulls the A/F ratio was around 10:1. I did some data logging and tweaking till I got the fuel trims where they should be and its running great. Haven't been back to the dyno (they closed the shop I was using) so I'll have to get another baseline done. With the PCM reprogrammed I would bet I've picked up 15 - 20 hp ... WOT runs now have the A/F ratio 12.5 - 13:1 measured with a wideband O2.

 

[96vetteLT4]

Save your money

While some will say it will be great the reality was 12 hp. That was with a recalibrated computer. The noise ,leaks , o2 sensor, and general pain in the a** wasnt worth it and I took them back off and put the stock exhaust manifold back on. You would be better off changing the rear to a 4:10 gear if you want the most performance for the $$. The stock LT4 exhaust is actually not that bad. You definately want the cat back exhaust upgrade but for me the headers weren't worth all the trouble for the small performance gain from a stock motor. Now if you change the cam, ect ...that might be different but in stock form I wouldnt spend the money....G

 

[Hib Halverson]

This question cannot be answered with any credibility unless we know how you are going to calibrate (reprogram) the ECM.

 

[Nick S]

Ok, these are good answers and they bring up something else that I was concerned about but did not mention ... reprogramming the computer. I spoke with a couple different mechanics that assured me that there would be no need for reprogramming the computer after installing headers. Clearly, these people were wrong or at the very least misinformed.

I assume the best way to have the computer reprogrammed would be with a dyno tune. That being said, what sort of luck have people had with these tune by mail places that send you a replacement computer which has be reprogrammed blindly based on the modifications to your car?

Nick

 

[Hrtbeat1]

Well technically you don't have to re-program your PCM, it will run and run fine it will just be rich. To take full advantage of the headers it is definately worth it to re-program.

I think JEFFNLSA got one of those re-programed PCM's from pcm4less done for his. He seems happy with his results. Maybe he will see this post and chime in.

One thing about re-programming these cars, or even dyno tuning. Not everybody has the right equipment. This was the first year for OBD2 and the last year of the C-4, the computer is different for the C-5, therefore there are only a few options for reprogramming this one year specific computer. LT1/4 Edit and the TunerCat/JET DST are the only two I know of.



G

 

[JEFNLSA]

I think JEFFNLSA got one of those re-programed PCM's from pcm4less done for his. He seems happy with his results. Maybe he will see this post and chime in.
G

JEFNLSA here.
I just sent my PCM to Brian @ www.pcmforless.com for the re-tune. He had it back to me in a couple of days. In fact, I think it was out of the car for a total of 4 days. I also had the Hotcam put in prior to the headers so, when I sent the PCM to him, he had a list of my mods and a tune ready to go for me. He's very familiar w/ the LTx engines (and the mods that go along w/ them), has a good reputation and seems to know how to get the most out of your tune..considering it's mail-order & not dyno.

I have no regrets w/ my EM LT headers. Of course, it's all part of the total package. I most likely wouldn't have done the headers alone had I not did the HC. They work very well in conjunction w/ each other & the 4.10's are just icing on the cake.

If I were not going to do the HC, or some heads/cam package in general, I'd most likely do the 4.10's first and go from there. Definitely some bang for your buck in the gear swap....and, don't know if LT's are worth it on a stock motor...but it'll definitely sound better.

Jeff

 

[LT4man]

Just wanted to echo what Jeff said. If you are going to go with a mail-order tune for your PCM, Brian at http://www.pcmforless.com is the ONLY way to go.

Their turn around time is amazing, the tune is stupendous and the price is affordable. They do NOT charge a Corvette tax! :L

How do I know this? Brian did mine!!!

SAVE THE