Thanks to all you die hard zr1 guys !!!!

[jamesjy]

Thanks so much to Pete, dynomite and several others that offer such helpful info on here.....I don't post much but always follow your helpful posts about the lt5...I just recently completed a top end port job that I did along with headers and exhaust on my 91. I ran up against a new gt mustang420hp on the streets tonight... He also had nitrous.... Needless to say, I think that punk is gonna be googling what an old school zr1 is because I waxed his a#^ four times tonight on various runs....don't know what my hp is now but when I hit third gear I pulled him like a pimp...very satisfying and thanks again to all you die hard lt5 guys

[XfireZ51]

Was he using the Nox?

[jamesjy]

Don't know what system he was running... Could see and hear him purging at red light.... Thought he would have pulled me....I do have tons of hours in porting the plenum and injector housings, obx headers,new injectors open air cleaner,a Doug rippie chip, and borla's with no cats... I figure I should be pushing around 450 flywheel.

1991 zr-1
1970 lt-1 conv
1972 w/zl-1
1965 conv w/zl-1

[Bob Eyres]

SPANK those Mustangs James

I hesitate to offer you advice after seeing that list of Corvette's you have, or have owned, but those Borla's you're running are one of the most restrictive aftermarket exhausts out there, I've had them. They sure do sound sweet, but I'll bet you pick up at least 10hp if you go to 3" all the way back. Let that puppy breathe.

[LGAFF]

The Borla restriction is in the resonator, it drops to 2.25"....put in an X pipe and you should be good

Thats if you have the 2.75 system

[Pete]

I bet he was using the Nos.

Let me just say this Mustangs push a lot of air (frontal area) and weigh 2 tons, 420 horsepower can only do so much I would think that Mustang runs 107-110 1/4 MPH I would gather to guess your making closer to 400 rwhp and you would run 117-120 1/4 MPH so I pretty sure he was shooting it with 100 heck even 150 shot he'd be just keeping up with you.

If you were pulling on him hard then he was on motor if you were door to door the Nos was used.

Pete

[mike100]

Conventional wisdom say to keep the oem 2.7" pipe size, but I was surprised to have actually felt a seat-of-the-pants difference when I went with the SW 3" system. Not as much as adding headers, but enough that I was glad I went thru the trouble.

I have the 412hp mustang too. Before headers, the mustang could stay ahead 1 car length on a run to 90mph. I have not had a chance to race my own car after recent mods, but the 91 has never run better.

The best thing you did was do all the mods at once. mine was more incremental and harder to tell the total power gain. You sort of get used to the 10-20hp steps- not as impressive as a 70hp overnight gain. Or should I say over-week(s) since I know the intake didn't port itself overnight

[jamesjy]

Thanks guys for all the input. I do have a 3" x- pipe and I was gonna consider changing the exhaust from headers back...the previous owner put the exhaust on so I figured before I spent any more money I would bolt it back up and see how it does. I am happy with the way it sounds...still pretty refined but I don't get headaches after 50 mile cruises from all the resonance. Any input and opinions would be greatly appreciated on what options there are out there...I hate to spend a bunch of money on a new exhaust that's loud as hell and gives me headaches for the sake of picking up 5 hp. I'm definitely not a candy a$& and don't mind loud exhaust.. But every other car I own is pretty darn loud. So it's nice to jump in the ole lt5 and cruise, and still carry on a conversation with the lady. I am gonna take her to the dyno this Wednesday and see where I'm at..will post results.

[alnukem]

I'm still amazed at how well our 25 year old cars hold their own with stock cams. Basically headers & porting. You might want to think about the FBI guys exhaust using the NPP flapper valves, it's a great compromise, only noisy when you're in it.

[WARP TEN]

Originally Posted by alnukem

I'm still amazed at how well our 25 year old cars hold their own with stock cams. Basically headers & porting. You might want to think about the FBI guys exhaust using the NPP flapper valves, it's a great compromise, only noisy when you're in it.

Or even the stock system with cutouts. I am liking mine more and more. Quiet in the neighborhood and my wife doesn't complain anymore. For a little nice sound I can crack them a bit and for full out add 10-15 hp open them all the way. Plus I save about 50 lbs without the spare tire and carrier. --Bob