85 Iroc vs 99GTP
85 Iroc vs 99GTP
I have a 85 Iroc with a 87 L98 out of a vette, we pulled the motor thats why I'm sure. Its bone stock
Dad has a 99 GTP with the 3.4 setup with all supporting mods.
He said I'd kill him off the line but he thinks he would comeback around me.
What do you guys think?
Dad has a 99 GTP with the 3.4 setup with all supporting mods.
He said I'd kill him off the line but he thinks he would comeback around me.
What do you guys think?
Supreme Member




Joined: Oct 2004
Posts: 4,528
Likes: 240
From: Henrietta NY
Car: 1984 Trans Am L69
Engine: Sniper EFI Powered 355
Transmission: WC T5 w/ Steel Support Plate
Axle/Gears: 3.42 10 Bolt Posi
Re: 85 Iroc vs 99GTP
What trans / rear do you have what are supporting mods?
Joined: May 2005
Posts: 728
Likes: 1
From: Toronto, Ohio
Car: 1991 Trans Am GTA
Engine: 355
Transmission: 4L60
Axle/Gears: 4th gen 10 bolt 3.42 posi
Re: 85 Iroc vs 99GTP
He'll end up with the win on this one. What are you running for a ECM in the IROC?
Member
Joined: Oct 2007
Posts: 496
Likes: 0
From: Winnipeg
Car: 91 GTA
Engine: L98
Transmission: 700R4
Axle/Gears: 3:73
Re: 85 Iroc vs 99GTP
should be a couple of 14second cars going at it.
i think the iroc will get the upper hand, providing its running tip top. i would do a small burn out to clean up the tires first then let em have it!
from factory are those gtp's 15second cars?
i think the iroc will get the upper hand, providing its running tip top. i would do a small burn out to clean up the tires first then let em have it!
from factory are those gtp's 15second cars?
Joined: May 2005
Posts: 728
Likes: 1
From: Toronto, Ohio
Car: 1991 Trans Am GTA
Engine: 355
Transmission: 4L60
Axle/Gears: 4th gen 10 bolt 3.42 posi
Re: 85 Iroc vs 99GTP
From what I've read and seen, the mods he is describing for the GTP would probably put it in the 13's (14 sec. car from factory). If he's not running the 87 vettes ECM, then it's not running right because the 305 TPI ECU in his IROC will not run the motor right at all. In all reality, due to some wiring differences I think he would need his stock ECM with a custom tune from somewhere like pcmforless if he didn't use the wiring and ECM from the vette.
Member
Joined: Oct 2007
Posts: 496
Likes: 0
From: Winnipeg
Car: 91 GTA
Engine: L98
Transmission: 700R4
Axle/Gears: 3:73
Re: 85 Iroc vs 99GTP
From what I've read and seen, the mods he is describing for the GTP would probably put it in the 13's (14 sec. car from factory). If he's not running the 87 vettes ECM, then it's not running right because the 305 TPI ECU in his IROC will not run the motor right at all. In all reality, due to some wiring differences I think he would need his stock ECM with a custom tune from somewhere like pcmforless if he didn't use the wiring and ECM from the vette.
budfreak, nice car btw. i like the direction your car is taken. how do you like the quality of the hood, looks sharp!
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Re: 85 Iroc vs 99GTP
Thanks for the responses.
Yes i do have the ecm from vette we bought the whole car for 700 bucks.
I have 3.42 rear out of a 4th gen.
His suppporting mods are slp cai, down pipe, Ubend delete, ZZP pcm, colder plugs, 3.4 pulley. Probably more i cant think of them all.
Hes wanting to go with a 3.1 pulley after he does his intercooler but hes thinking he may need heads or head work to do it without knock.
Hes always scanning for knock
Well anyway we went about 10pm that supercharger loved the cool air that night.
3rd honk and yes i blasted him off the line. He slowly launched his car, hes scared of breaking tranny.
Bit it was all over with by 50 or maybe a little more, he was around me and pulling. we shut down then.
No need in abusing engine when the point is proven
Yes i do have the ecm from vette we bought the whole car for 700 bucks.
I have 3.42 rear out of a 4th gen.
His suppporting mods are slp cai, down pipe, Ubend delete, ZZP pcm, colder plugs, 3.4 pulley. Probably more i cant think of them all.
Hes wanting to go with a 3.1 pulley after he does his intercooler but hes thinking he may need heads or head work to do it without knock.
Hes always scanning for knock
Well anyway we went about 10pm that supercharger loved the cool air that night.
3rd honk and yes i blasted him off the line. He slowly launched his car, hes scared of breaking tranny.
Bit it was all over with by 50 or maybe a little more, he was around me and pulling. we shut down then.
No need in abusing engine when the point is proven
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Joined: Feb 2006
Posts: 7,260
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From: Manteca,California. Nor Cal.
Car: SOLD IT. Mopar guy only now.
Engine: gone
Transmission: gone
Axle/Gears: gone
Re: 85 Iroc vs 99GTP
got smoked! haha. j/k sounds fun althought I do not condone street racing but it sounds to me like you guys had it under control
Re: 85 Iroc vs 99GTP
Yeah no need to go to any insane speeds when the point is done. Lol hes faster. This actually his acct. He was using to find my car, and do some research lurking around. I need to get some pics up.
He wants te get me as quick as him at the track, depending on track and weather hes run 8.6 to high 8 till he broke his first tranny.
Oh thats in the 1/8 mile of course.
He wants te get me as quick as him at the track, depending on track and weather hes run 8.6 to high 8 till he broke his first tranny.
Oh thats in the 1/8 mile of course.
Joined: Sep 2004
Posts: 5,906
Likes: 240
From: Chicagoland Suburbs
Car: 1989 Trans Am GTA
Engine: LT1, AFR 195cc, 231/239 LE cam.
Transmission: M28 T56
Axle/Gears: 3.23 10bolt waiting to explode.
Re: 85 Iroc vs 99GTP
Pretty much what I expected to happen. Anytime you do a pulley with a supercharged GTP its gonna go alot faster.
Supreme Member

Joined: Jan 2003
Posts: 2,043
Likes: 3
From: San Diego
Car: 1994 Trans Am
Engine: LT1
Transmission: Auto
Axle/Gears: 3.23
Re: 85 Iroc vs 99GTP
Yeah, pullied GTPs are no joke for a TPI car. Mine was low 13's high 12's@105 with the following mods: 3.25 pulley, fenderwell intake, 1.9 rockers, ported exhaust manifolds, 3" downpipe, cutout, and a custom mail order tune. This was back in 2004 before I crashed it.
I wanted to do a 2.9 pulley, TOG headers, and an alky injection with a new tune.
A stock GTP puts down 190-200whp and 270wtq. With just a pulley/intake/ubend removed, they put down around 230whp/310wtq.
I wanted to do a 2.9 pulley, TOG headers, and an alky injection with a new tune.
A stock GTP puts down 190-200whp and 270wtq. With just a pulley/intake/ubend removed, they put down around 230whp/310wtq.
Joined: Sep 2004
Posts: 5,906
Likes: 240
From: Chicagoland Suburbs
Car: 1989 Trans Am GTA
Engine: LT1, AFR 195cc, 231/239 LE cam.
Transmission: M28 T56
Axle/Gears: 3.23 10bolt waiting to explode.
Re: 85 Iroc vs 99GTP
Yeah, pullied GTPs are no joke for a TPI car. Mine was low 13's high 12's@105 with the following mods: 3.25 pulley, fenderwell intake, 1.9 rockers, ported exhaust manifolds, 3" downpipe, cutout, and a custom mail order tune. This was back in 2004 before I crashed it.
I wanted to do a 2.9 pulley, TOG headers, and an alky injection with a new tune.
A stock GTP puts down 190-200whp and 270wtq. With just a pulley/intake/ubend removed, they put down around 230whp/310wtq.
I wanted to do a 2.9 pulley, TOG headers, and an alky injection with a new tune.
A stock GTP puts down 190-200whp and 270wtq. With just a pulley/intake/ubend removed, they put down around 230whp/310wtq.
Joined: May 2005
Posts: 728
Likes: 1
From: Toronto, Ohio
Car: 1991 Trans Am GTA
Engine: 355
Transmission: 4L60
Axle/Gears: 4th gen 10 bolt 3.42 posi
Re: 85 Iroc vs 99GTP
Thank you. The hood is very nice. It could fit a little bit better, but I think that can be remedied and I just can't figure out how (I'm not a body man and I've made all the adjustments and changes I can figure out to make).
Re: 85 Iroc vs 99GTP
Would the stock heads breath with headers and a new tune and maybe rockers at a 3.1 pulley without knock? I was going to intercool it but if i can get by without it. Friend of mine blew his up, never scanning for knock. He threw on a 3.4 pulley and let it go at that.
Joined: Sep 2004
Posts: 5,906
Likes: 240
From: Chicagoland Suburbs
Car: 1989 Trans Am GTA
Engine: LT1, AFR 195cc, 231/239 LE cam.
Transmission: M28 T56
Axle/Gears: 3.23 10bolt waiting to explode.
Re: 85 Iroc vs 99GTP
You will have trans problems eventually though.
Re: 85 Iroc vs 99GTP
Yeah as my son said earlier I've already broken one. Thats why I won't full bore launch the thing anymore, its also my daily driver. My wife drives a 07 gxp, thought that would be fun but almost no aftermarket for it. My GTP would bust its ***.
What would be the best banf for the buck for my son exhaust? I know the TPI isn't a great breather but i have seen fast TPI's before.
What would be the best banf for the buck for my son exhaust? I know the TPI isn't a great breather but i have seen fast TPI's before.
Joined: Sep 2004
Posts: 5,906
Likes: 240
From: Chicagoland Suburbs
Car: 1989 Trans Am GTA
Engine: LT1, AFR 195cc, 231/239 LE cam.
Transmission: M28 T56
Axle/Gears: 3.23 10bolt waiting to explode.
Re: 85 Iroc vs 99GTP
Yeah as my son said earlier I've already broken one. Thats why I won't full bore launch the thing anymore, its also my daily driver. My wife drives a 07 gxp, thought that would be fun but almost no aftermarket for it. My GTP would bust its ***.
What would be the best banf for the buck for my son exhaust? I know the TPI isn't a great breather but i have seen fast TPI's before.
What would be the best banf for the buck for my son exhaust? I know the TPI isn't a great breather but i have seen fast TPI's before.
There are many things you can do. I'm a big proponent of a HSR swap. Simply because of the huge power gains. The peak power gain is small, but the extra 1000rpm of power you get above 4500rpm really wake the car up and make it more fun to drive. But I have an LT1 and I love its powerband. I really don't notice the missing torque. Sure, its gone on paper but I hardly notice it because of the way an LT1 likes to rev. Even with a small cam an LT1 will pull hard to 6k, HSR's are the same way. And with the right cam and heads they'll pull even higher.
Member
Joined: May 2008
Posts: 377
Likes: 0
From: MN
Car: 86 Z28
Engine: 350 TPI
Transmission: T56
Axle/Gears: 3.42 posi
Re: 85 Iroc vs 99GTP
I raced a coworker in his gtp with my Z28, both cars had mild mods on them, they were side by side, but whenever mine shifted it would pull away a little.
Supreme Member

Joined: Jan 2003
Posts: 2,043
Likes: 3
From: San Diego
Car: 1994 Trans Am
Engine: LT1
Transmission: Auto
Axle/Gears: 3.23
Re: 85 Iroc vs 99GTP
Get right out of town!! Can you tell that story again? Kidding. A good running L98 with the right mods will still hang with a mildly modded GTP. But in terms of $/hp the GTP starts shining very quickly.
Member
Joined: May 2008
Posts: 377
Likes: 0
From: MN
Car: 86 Z28
Engine: 350 TPI
Transmission: T56
Axle/Gears: 3.42 posi
Re: 85 Iroc vs 99GTP
we raced a couple times on some roads in mexico and he claimed i jumped on him, but it was pretty close, the l98 pulled a little better though, especially at lower rpm after shifting.
My "l98" isn't an l98 though, 350 block from 1968 with 487 heads and unkown cam right now...
My "l98" isn't an l98 though, 350 block from 1968 with 487 heads and unkown cam right now...
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