here's my setup: 305 H.O. w/11k miles on it,700r4,3.73 this car is rated 190hp/240tq stock.......I've ditched the entire stock exaust and replaced it with headman shorty 1 5/8" headers & 2.5" Y-pipe/2.5" HF stainless cat/3" stainless Borla cat back adjustable system. whether the escape flange is open or closed,I"m not sure it makes too much difference with my engine. how much HP wise,would this extra breathing room benifit a stock L69 motor?? ported heads/cam/intake on same motor? anyone here actually dyno a car after installing better exaust??

 

I would say with headers you get 15hp and 10hp out of the cat-back.

 

so 10 for the headers and 15 for the cat/catback....roughly,so 10+15=25 extra horses....? seems a bit much,but I know ignition and carb modification alone will get about that out of a stock L69. 215HP doesn't seem too far fetched. I've never lost to a 4thgen V6,so it's possible that I'm getting those extra 10-20 horses more than 190 at WOT or those guys(& girls) just don't know how to drive those 200 horse V6s....he he.what the hell is wrong with me..?

 

Junkyard,

I did do that. Overall, the peak HP and Tq went up by 10 units. However, there were points in the midrange, where the difference was 20-25 units. I went from ported stock exhaust manifolds on an Xfire, to TPIS longtubes with full emissions.

 

intersting......I have the smog leagal version of hedmans shorties myself....I'm convinced it does little to compromise performance on a stock motor. I can't wait to change the cam & do something about the heads too. the factory Q-jet and HEI can do the job as long as it's running right,good money saved for real mods. 25 extra horse from exaust alone?? nice to know I don't have $1100 worth of exaust just for looks! I never really planned on benifiting much from the exaust right away with my stock motor,my longterm goal was to utilize the full flow capabilities of my setup w a more heavy breathing engine. it's cool that it has already free'ed up some power from my existing engine.

 

Remenber that when you add Mods, you can not just ADD everthing up and say this my new Horsepower and Torque.

 

WOW...I'm almost up to 300hp!! I'll post my dyno results when I have the $50 to drop on a dyno test....it's really tough to pindown exactly how much the exaust helps a stock engine...definity helps but how much?? I seriously doubt that headers rob low end torque.....bull$hit!! I'll even hit the drag way when I'm not broke anymore and I can afford to break stuff! also,my friend who bought my 3000GT is going to dyno test it.......it should be interesting,218 stock.....maybee the K&N filter will kick that up to 219-220??

 

i always thought the L69 cars got a 2 3/4 intermediate pipe from the factory...so why did you downgrade?

 

He didn't he got a 3" Borla Cat-back.

 

oops..to many diameters and im sick..i missed that.

 

There have been articles published where the magazine Dyno tested the L69 and came up with well over 200 horsepower.....even though the factory rated it at 190.

What happens often is manufacturers will play games with horsepower and engine displacements in order to affect the insurance rates accordingly.

Who knows? The L69 is pretty darn quick though.