All,

This summer I am planning on modding my vette with the following:

Long tube headers
Free flow cat
Walker Y-pipe with crossover
Borla or Monza muflers

What I am wondering is how much torque will I loose? I know that the L-98 depends on backpressure for torque, but how much will I loose and how loud will the car be with this setup?

Next year I am going to do the rockers and port the plenum. If I have the $$ Also get larger TPI runners. I dont know if porting the manifold will do much good. I plan on sticking with my current TB or going to a 52MM TB.

My goal by the end of next year is to have a really nice sounding Corvette that has a bark as bad as its bite.

Thanks

George

 

I don't think you will loose much. I have done all of this. My quarter mile times have come up a bit, and the 60' down a hair. I don't think I lost any torque, I think I'm just spinning the tires more off the line. I have tpis 1 3/4" headers (I was also concerned about losing torque), no cat, and 2 1/2" Borla catback. I asked TPIS if I would lose torque with their headers and they said no.

I would say the biggest improvement came from removing the cat, but mine was really clogged and probably partially clogged since I bought the car. Also I put on the catback while I was gutting the cat, so that makes it hard to tell.

I think the headers made it pull a little harder throughout the rpms. I think I will be able to pick up at least 2 tenths with them, but so far less then 1. I think it is the driver.....I really think I should be at 13.5 with no other mods. I just keep spinning the tires, I'll let up early, or last time I accidently left the car in 2nd gear!!!! Whoops. I still ran a 13.88 and blew away my brothers porsche 944t. I was too busy watching his first run to drive my car! :bb

 

Long tube headers give more midrange torque. My car spun the tires more after putting on headers. As for loudness, it will be a lot louder than stock. My car with 2 1/2" borlas have a nice burble at idle and sound awesome at WOT. If you want a little bark, this is it. Mine has resonance but I don't have a Y pipe with a crossover. I originally had 2 1/4" borla and they were quieter than the 2 1/2" (and had less resonance), so you should be alright.

 

You will have more torque at all RPMS with headers. The idea of L98s needing backpressure is an old wives tale. SLP actually found that bone stock L98s made more horsepower and torque at all RPMs with 1 3/4" headers vs. 1 5/8". They don't know why the 1 3/4" didn't cause a power loss at low RPMs, but the fact is, they didn't. TPI cars respond very well to intake and exhaust modifications.

 

You will not lose torque, unless you put a huge (1 7/8 or bigger primaries) se on the car. You will GAIN gobs of torque.

PS, I have a set of TPIS long tubes for sale that will work nicely. Make offers.

(no I am not just blowing smoke about torque tomake a sale.)

 

cramey, how much for the headers and what will the fit?

Dave

 

gtpclub, I think you're basically on the right track. I would consider a different order to your mods. With stock intake, cam heads etc., installing headers (esp. 1 3/4") will not offer you much of a gain. Here's why: a stock L98 does not have difficulty getting air *out* of the motor, but has major issues getting enough air *in*. Having made all the mods you're thinking about, and then some, I would do the headers *last* and install an Accell base and large tube runners or ASM runners along with your 52mm TB. Your hi-flow cat is a good idea. If your car has pre-cats, a "Y" pipe replacement will give you some ~10 hp. Headers are a major PITA, and you would wonder why the gain wasn't worth the pain. I would also take exception to the notion that there is no loss of low end. I noticed it immediately, that my power curve shifted higher in the rev range by at least 500 rpm's. It pulled harder up high, but definitly lost some bottom end. This includes the split set of 1.5 / 1.6 RR's, full intake, etc. etc