12's
Member
Joined: May 2006
Posts: 254
Likes: 0
From: Lake of the Ozarks, Missouri
Car: 1987 Pontiac GTA Trans Am
Engine: Basic Stroked SBC..383
Transmission: PerformaBuilt 700R4 3000 Stall
Axle/Gears: Moser 9in. 3:70s
Re: 12's
Mine is. Im not done with it yet but I would think Id be in the 11s easy on motor and 10s on the bottle.
Old set up with Nitrous 12.8s at 108-110 MPH.
Bone stock L98 with a 75 shot, Nothing other than the nitrous.
Eld. Shortys with SLP Loud mouth
Stock 700R4..didnt last long..(4 rebuilds in a year)
Moser 9in 3:70s
Micky T DRs on the GTA Wheels.
Suspension..Spohn Panhard bar and Control arms
NOW
350 .040 over
Eagle Stroker kit (ESP 12011).. what is that like 387-388 CID? I dont know
Comp Cams 260/262 .630/630 R106s
Demon 750 Carb
Wiend Team G High Rise
Brodix Race Heads Stainless Valves
Motor Build by Boyds Racing in Norman, OK.
500 hp on 93 octain.
Build for Nitrous.. prob only spray a 150-175 shot.
Tranny now
Performabuilt 700R4 3000 Stall http://performabuiltautomatics.com/G...00r4_4l60e.htm Great people..
Supsenion
Cheap Coil over in the front with Lakewood 90/10s
Spohn Adj Torque Arm
" " Panhard bar
" " Control Arms
and BMR Subframe con.
Pretty much Stock weight of an 87 GTA
One thing Do I need the 50/50s for the rear?
If I can drive and hook what does it look like?
Old set up with Nitrous 12.8s at 108-110 MPH.
Bone stock L98 with a 75 shot, Nothing other than the nitrous.
Eld. Shortys with SLP Loud mouth
Stock 700R4..didnt last long..(4 rebuilds in a year)
Moser 9in 3:70s
Micky T DRs on the GTA Wheels.
Suspension..Spohn Panhard bar and Control arms
NOW
350 .040 over
Eagle Stroker kit (ESP 12011).. what is that like 387-388 CID? I dont know
Comp Cams 260/262 .630/630 R106s
Demon 750 Carb
Wiend Team G High Rise
Brodix Race Heads Stainless Valves
Motor Build by Boyds Racing in Norman, OK.
500 hp on 93 octain.
Build for Nitrous.. prob only spray a 150-175 shot.
Tranny now
Performabuilt 700R4 3000 Stall http://performabuiltautomatics.com/G...00r4_4l60e.htm Great people..
Supsenion
Cheap Coil over in the front with Lakewood 90/10s
Spohn Adj Torque Arm
" " Panhard bar
" " Control Arms
and BMR Subframe con.
Pretty much Stock weight of an 87 GTA
One thing Do I need the 50/50s for the rear?
If I can drive and hook what does it look like?
Thread Starter
Supreme Member




Joined: Dec 2005
Posts: 9,902
Likes: 874
From: 53.0907° N, 113.4695° W
Joined: Sep 2003
Posts: 25,895
Likes: 429
From: Pittsburgh PA
Car: 89 Iroc-z
Engine: 555 BBC Turbo
Transmission: TH400
Axle/Gears: MWC 9” 3.00
Re: 12's
If I can drive and hook what does it look like?
550 atleast. should go bottom 11's at over 123-124 mph in a pretty light 3400-3500 lb raceweight. my car is milder than that and i run 11.50's, about 400whp which is 480-500 on crank Member
Joined: May 2006
Posts: 254
Likes: 0
From: Lake of the Ozarks, Missouri
Car: 1987 Pontiac GTA Trans Am
Engine: Basic Stroked SBC..383
Transmission: PerformaBuilt 700R4 3000 Stall
Axle/Gears: Moser 9in. 3:70s
Re: 12's
They hooked up my buddys motor for his nova on the dyno..pretty close set up but with eldelbrock heads and smaller cam and his made 490 at the flywheel and they said mine should be higher than that. I guess his heads arent really as good as mine idk. Im going down to OK Next weekend or the next to get it and well see how seh does. It would be bad *** to pull a tire or both!!
Senior Member
Joined: Nov 2000
Posts: 601
Likes: 0
From: Queen Creek, AZ
Car: 91 Formula
Engine: 383 HSR
Transmission: 5th 700R4
Axle/Gears: 3.89
Re: 12's
So what do you think about going with 1.7 RR's on my Setup to bump up the lift a little more or should I just step up to a solid roller and keep the 1.6's and I definately agree I need more Stall, I'm going for a 3600 when I switch over to a TH350 probably this winter.
Joined: Sep 2003
Posts: 25,895
Likes: 429
From: Pittsburgh PA
Car: 89 Iroc-z
Engine: 555 BBC Turbo
Transmission: TH400
Axle/Gears: MWC 9” 3.00
Re: 12's
i woudlnt try 1.7's. i was told it starts to mess with valve train geometry and is hard to control at higher rpms with the extra long pushrods
you may get away with a 1.65 ratio but i'd just keep the 1.6's for now
you may get away with a 1.65 ratio but i'd just keep the 1.6's for now
Supreme Member
iTrader: (1)
Joined: Jan 2008
Posts: 1,428
Likes: 0
From: Sacramento Ca
Car: 91 Pontiac Firebird
Engine: Killer SBC, w/ RV cam
Transmission: AutoMatic, w/ shift kit
Axle/Gears: Posi-Traction
Thread Starter
Supreme Member




Joined: Dec 2005
Posts: 9,902
Likes: 874
From: 53.0907° N, 113.4695° W
Re: 12's
Curious as to how much has changed in the 8 years since this thread was active.
Lots of carbed Gen I small blocks doing their thing then.
I bet there are a lot more in the 12 second crowd now. Probably plenty of stock or nearly stock LS swaps out there too.
While I've been in the 12's for a while now, I haven't yet tested my latest combination on top of the old 355. While I doubt 11's are in the works, it's gotta be faster than before. Personal best with the unported heads and 274 cam was a corrected 12.4 @ 108 (+/-). I'm thinking a couple of tenths with ported heads and 288 cam. Maybe a couple of more tenths with a better converter and true dual exhaust. Maybe 11's.
Lots of carbed Gen I small blocks doing their thing then.
I bet there are a lot more in the 12 second crowd now. Probably plenty of stock or nearly stock LS swaps out there too.
While I've been in the 12's for a while now, I haven't yet tested my latest combination on top of the old 355. While I doubt 11's are in the works, it's gotta be faster than before. Personal best with the unported heads and 274 cam was a corrected 12.4 @ 108 (+/-). I'm thinking a couple of tenths with ported heads and 288 cam. Maybe a couple of more tenths with a better converter and true dual exhaust. Maybe 11's.
Last edited by skinny z; Oct 25, 2016 at 03:15 PM.
Senior Member
iTrader: (4)
Joined: Jun 2014
Posts: 667
Likes: 16
From: Brainerd, MN
Car: '84 Trans Am
Engine: 357 SBC
Transmission: 700R4
Axle/Gears: 10 Bolt 3.73, Torsen Diff
Re: 12's
What were you running for a converter and exhaust? I'll be interested to see what you end up with since our builds are so similar, although your cam is a little more aggressive.
Thread Starter
Supreme Member




Joined: Dec 2005
Posts: 9,902
Likes: 874
From: 53.0907° N, 113.4695° W
Re: 12's
When I ran the XR276HR Vortec headed 353, I had a TCI 10" converter and Hedman LT (but really mid-length) headers into a 2 1/2" x 2 to 3" y-pipe. From there to the back via a Flowmaster 3" cat-back (with no cat) to a crappy Flowmaster muffler in the stock location.
The exhaust certainly cripples the cars performance at the track. I can gain a tenth and almost 2 MPH in the 1/8th just by bypassing the muffler with a cut-out placed just in front of it at the turn.
The converter allowed me to foot brake to about 2200 RPM at the most. Flash stall was arguably around 3500 judging by the tach when the car was on the chassis dyno.
Race weight waiting at the tree is 3650 lbs.
12.75 @ 105.93, 8.082 @ 83.39, 1.74 60’ (Density altitude was 2050').
12.449 @ 108.551 MPH corrected.
The exhaust certainly cripples the cars performance at the track. I can gain a tenth and almost 2 MPH in the 1/8th just by bypassing the muffler with a cut-out placed just in front of it at the turn.
The converter allowed me to foot brake to about 2200 RPM at the most. Flash stall was arguably around 3500 judging by the tach when the car was on the chassis dyno.
Race weight waiting at the tree is 3650 lbs.
12.75 @ 105.93, 8.082 @ 83.39, 1.74 60’ (Density altitude was 2050').
12.449 @ 108.551 MPH corrected.
Last edited by skinny z; Oct 25, 2016 at 02:02 PM.
Senior Member
iTrader: (4)
Joined: Jun 2014
Posts: 667
Likes: 16
From: Brainerd, MN
Car: '84 Trans Am
Engine: 357 SBC
Transmission: 700R4
Axle/Gears: 10 Bolt 3.73, Torsen Diff
Re: 12's
Are you planning on staying with the 3" cat-back, or do you plan on moving up in diameter?
Thread Starter
Supreme Member




Joined: Dec 2005
Posts: 9,902
Likes: 874
From: 53.0907° N, 113.4695° W
Re: 12's
I'm thinking I'll redo the exhaust in it's entirety. New headers although I'll probably stick with 1 5/8". From there I'll go with Holley's Black Heart duals. That'll bump up my intermediate pipe sizes from a single 3" to 2 x 2 1/2" but more importantly, I'll have a pair of mufflers to work with rather than the single I have now. Following the generally applied rule of 2.2 CFM/ HP, that means instead of a single muffler with an 800+ CFM capacity, I can use a pair of mufflers with 400 CFM each. Much easier to design and definitely much quieter than a single 800 CFM muffler. That should make the biggest improvement.
If I get really frustrated and haven't managed that wholesale change by the end of the next racing season, I may go a temporary route and hang a couple of mufflers off the headers. Get the length right and with properly spec'd mufflers, it'll be as good as an open exhaust (or very close to). Ground clearance will suffer though.
If I get really frustrated and haven't managed that wholesale change by the end of the next racing season, I may go a temporary route and hang a couple of mufflers off the headers. Get the length right and with properly spec'd mufflers, it'll be as good as an open exhaust (or very close to). Ground clearance will suffer though.
Senior Member
iTrader: (4)
Joined: Jun 2014
Posts: 667
Likes: 16
From: Brainerd, MN
Car: '84 Trans Am
Engine: 357 SBC
Transmission: 700R4
Axle/Gears: 10 Bolt 3.73, Torsen Diff
Re: 12's
It's sort of a balancing act with these cars when you plan to street drive them at all. I wouldn't mind the black heart setup, but it's tough to justify the cost to myself. In the end I'll probably end up with a 3" exhaust. I'd like to just fab up my own 3.5" single, but I don't want to blindly buy a bunch of bends and hope I can make it work. Unfortunately, neither of my cars came with a full exhaust, so I don't have anything to compare and/or measure.
Thread Starter
Supreme Member




Joined: Dec 2005
Posts: 9,902
Likes: 874
From: 53.0907° N, 113.4695° W
Re: 12's
There are/were aftermarket 3-1/2" and 4" over the axle packages available for these cars although I can't say if they're still produced or not. Unless you get imaginative, you still have to deal with a single muffler though. That's the biggest bottleneck.
The Black Heart system aside, I've thought that about the best arrangement for these cars as street cars is to buy a reasonable 3" single over the axle exhaust, single muffler and all and have cut-outs placed at the correct distance from the collectors. That's the hot ticket for a dual purpose car. At least when the ground clearance and chassis fitment are a problem as they are on third gens. Particularly lowered ones.
The Black Heart system aside, I've thought that about the best arrangement for these cars as street cars is to buy a reasonable 3" single over the axle exhaust, single muffler and all and have cut-outs placed at the correct distance from the collectors. That's the hot ticket for a dual purpose car. At least when the ground clearance and chassis fitment are a problem as they are on third gens. Particularly lowered ones.
Supreme Member
Joined: Jun 2006
Posts: 1,422
Likes: 1
From: alliance, ohio
Car: 1984 chevy camaro
Engine: 355
Transmission: turbo 350 2800 stall
Axle/Gears: 3:73 detroit locker posi
Senior Member

Joined: Feb 2008
Posts: 706
Likes: 0
From: Central PA
Car: 1990 IROC
Engine: Rebuilt L98 with H/C/I/Carb
Transmission: TH350 with ATI Treemaster
Axle/Gears: 7.5 with 4.10's
Re: 12's
Single 3" into a dynomax muffler on my car with a "worked over" mufflex y-pipe. At our power level (I was running high 11's...gunning for low 11's now), the single 3" isn't hurting too much.
Thread Starter
Supreme Member




Joined: Dec 2005
Posts: 9,902
Likes: 874
From: 53.0907° N, 113.4695° W
Senior Member

Joined: Feb 2008
Posts: 706
Likes: 0
From: Central PA
Car: 1990 IROC
Engine: Rebuilt L98 with H/C/I/Carb
Transmission: TH350 with ATI Treemaster
Axle/Gears: 7.5 with 4.10's
Re: 12's
Ultra-Flo I believe. It has a single inlet and outlet. It has been on there since 2000 or so.
Thread Starter
Supreme Member




Joined: Dec 2005
Posts: 9,902
Likes: 874
From: 53.0907° N, 113.4695° W
Re: 12's
The reason I ask is because I'm also running a single 3" muffler although in this case it's the last in line Flowmaster. It's possibly 300 CFM and that absolutely kills performance. I had thought about one of the race mufflers from the likes of Borla but those things are loud.
The best move I think in my case is to go either with something like Holley's new duals or keep the single 3" but add cutouts near the collectors.
The best move I think in my case is to go either with something like Holley's new duals or keep the single 3" but add cutouts near the collectors.
Senior Member

Joined: Feb 2008
Posts: 706
Likes: 0
From: Central PA
Car: 1990 IROC
Engine: Rebuilt L98 with H/C/I/Carb
Transmission: TH350 with ATI Treemaster
Axle/Gears: 7.5 with 4.10's
Re: 12's
I'm guessing mine must flow pretty well. I once unhooked right behind the Y Pipe at the strip and it made no difference in my ET. It isn't loud at all with the muffler in place.
I agree with you though...your system may be hindering your performance a good bit.
I agree with you though...your system may be hindering your performance a good bit.




