b727pic

iTrader: (1)

Not trying to start any wars. We all know LT's make more power. There are many of us for varying reasons that have few options when it comes to headers and passing SMOG checks.

On the Dyno my setup maxes out at 650HP / 625TQ @ 5600 RPM, boost still builds to redline (6500) but HP flatlines. There has been much speculation as to why, so in an effort to narrow down the actual cause I thought I would gather as much real world data as possible. I am starting to think the 1 5/8th primaries on my JBA shorties simply have reached their limit on CFM capacity???

Please check your HP range, and feel free to post up your setup.

The Mighty Texan

iTrader: (4)

Couldnt you just go with a catted y pipe?

b727pic

iTrader: (1)

Not familiar with "y" pipe setups? I currently have dual 2.5" running through Cat-less mids, and Magnaflow catback. Previously I had a Corsa Touring on my old 408 setup, had the same issue. The magnaflow, outflows the Corsa setup by quite abit, yet here I am with the same issue. If its in the exhaust, its got to be the manifolds themselves.

The Mighty Texan

iTrader: (4)

Oh gotcha I didnt realize that, couldn't you put preformance cats in the mids then? What im getting at is yeah LTs are going to get rid of the "weak link" specialy in your case! If its due to emissions couldnt cats somewhere in the exhaust be enough for you to get LTs, pass, and solve your problem?

b727pic

iTrader: (1)

Not legally. The visual inspections here in Cali mandate OEM placement of the CATS. Plenty of catted LT's systems available, I just don't want to have to deal with possible road side inspections, and removing them every two years (Im an old fart). Hence my dilema!!! nothing wrong with 650HP on a quasi smog legal setup, I just know my setup has more in it

hitmanws6

iTrader: (20)

You just said you had shorties with cats, then you have catless mids? Honestly being that I live in CA unless you are being stupid you wont get bothered and if you have cats even if they aren't in the right place. Yes the shorties are definitely holding you back. If you have mids what you can do for a little more power is port the primaries (assuming you have MAC mids) and cut off the flange and have a v band clamp welded on to it. That way you could run dual 3 inch midpipes to a good y merge to the catback

b727pic

iTrader: (1)

Currently the car is running Cat-less JBA 2.5" midpipes for the tuning process only. I have burned up two sets of CATS over the last few years, between rich AFR's and high CFM the CATS just were not holding up. Once tuned I have a new set of CATS ready to be installed. So once the tuning is done (almost done) then I will be back to a CATTED setup.....sorry for any confusion.

Nope....JBA, mods are in my sig. I have thought about the V band setup though. just not sure how effective that would be,if in fact its the primary tube that is the source of the bottle neck?

The whole point of this thread is to see how far shorty headers have been pushed to succesfully

Steve Gunn

I'm sorry I don't have an answer to your question of power limits, but JBA has 1 3/4 primaries for the vette, but none for the Fbody or GTO as far as I know, no one does. It would seem like a guy could get pretty creative with a custom set or adapted vette headers with a CARB plate tacked on then recoated. (but that would just be wrong ) Could you get a custom grind cam for your exact situation to squeeze more out of it?