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Old 07-10-2006   #1
torqueaddict
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suggested mods - 400 HP from 1989 L98

I'm curious what combinations have worked well for others with this motor to get performance in the high 12s to low 13s from a 3rg gen L98 f-body.

I have a low mileage 89 GTA - 5.7 Auto and I want to get at least 4th gen performance from it. It's stock besides the flowmasters, and it has the dual cat option.

I want to keep the original motor but I'm open to intake, heads, cam, and exhaust mods or even a blower. I already bought subframe braces since I have T-Tops. I also want to put in a 5 or 6 speed.

Most of the articles I've run across are for 4th gen. I bought a bunch of car mags from ebay to learn more about these motors but I don't know that all of the parts are still available from the early 90s when the mags were printed.

thanks for any advice!
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Old 07-10-2006   #2
hydraulicdave
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Re: suggested mods - 400 HP from 1989 L98

torqueaddict,
I have achieved 13.4s in my "88 GTA before I made a drastic changeover this past spring to my top-end.. What I had prior was this/ FlowMaster 80 series 3" cat(stock) back, JET-HOT Hooker shorty headers(15/8),75 shot(dry system)Nitrous(ZEX),Air Foil, SLP Air Box w/ K&N Filter, Walbro fuel pump, and a set of Kuhmos.. Now, this past Spring, I redid the whole top end & changed out my stock Cat-Catco. Have not touched the bottom end. I have a shift kit prior to my major top-end change. Haven't raced it yet, had it dynoed tuned and got 348 at the rear wheels w/ stock cat w/ a 125 shot. Get rid of that stock cat-chage it over--what a difference-you can hear it suck more air-which is one of the key components you need. I hope this helps you Man!!! Any questions you have-feel free to e-mail.....
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Old 07-10-2006   #3
strc09
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GTA Year: 1988
GTA Engine: Custom
Re: suggested mods - 400 HP from 1989 L98

I have an American Thunder Flowmaster 3" system on my car with no cats and a set of Hooker shorties. As for the other mods, I would say definately an SLP intake and runners or upgrade to the Accel or Stealth Ram system. I've heard good stuff about those. Also the addition of a CAI or functional ram air system along with an upgrade throttle body and airfoil could also help. Then again...you could always make your L98 into a 406.
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GTA: Grand Turismo Americano (Grand Touring America)
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Old 07-10-2006   #4
graphicideas1
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Re: suggested mods - 400 HP from 1989 L98

Quote:
Originally Posted by hydraulicdave
torqueaddict,
I have achieved 13.4s in my "88 GTA before I made a drastic changeover this past spring to my top-end.. What I had prior was this/ FlowMaster 80 series 3" cat(stock) back, JET-HOT Hooker shorty headers(15/8),75 shot(dry system)Nitrous(ZEX),Air Foil, SLP Air Box w/ K&N Filter, Walbro fuel pump, and a set of Kuhmos.. Now, this past Spring, I redid the whole top end & changed out my stock Cat-Catco. Have not touched the bottom end. I have a shift kit prior to my major top-end change. Haven't raced it yet, had it dynoed tuned and got 348 at the rear wheels w/ stock cat w/ a 125 shot. Get rid of that stock cat-chage it over--what a difference-you can hear it suck more air-which is one of the key components you need. I hope this helps you Man!!! Any questions you have-feel free to e-mail.....
hydraulicdave - Do you still have the slp airbox - want to sell?
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Old 07-10-2006   #5
Klortho
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Re: suggested mods - 400 HP from 1989 L98

Best mod to get the GTA into the mid 12's....LT1 or LS1

Or a 200 shot on the L98
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Old 07-11-2006   #6
hydraulicdave
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Re: suggested mods - 400 HP from 1989 L98

The SLP airbox is still in my car-still an important componentno, I don't want to sell.
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Old 07-11-2006   #7
hydraulicdave
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Re: suggested mods - 400 HP from 1989 L98

Quote:
Originally Posted by Klortho
Best mod to get the GTA into the mid 12's....LT1 or LS1

Or a 200 shot on the L98
Unless you build the bottom end-I've been told that 125 is a safe limit on a stock L98. There is always someone that pushes the envelope. I look to be the 12s whenever I race it next month w/ the top-end upgrades I did recently.
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Old 07-11-2006   #8
hydraulicdave
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Re: suggested mods - 400 HP from 1989 L98

Quote:
Originally Posted by torqueaddict
I'm curious what combinations have worked well for others with this motor to get performance in the high 12s to low 13s from a 3rg gen L98 f-body.

I have a low mileage 89 GTA - 5.7 Auto and I want to get at least 4th gen performance from it. It's stock besides the flowmasters, and it has the dual cat option.

I want to keep the original motor but I'm open to intake, heads, cam, and exhaust mods or even a blower. I already bought subframe braces since I have T-Tops. I also want to put in a 5 or 6 speed.

Most of the articles I've run across are for 4th gen. I bought a bunch of car mags from ebay to learn more about these motors but I don't know that all of the parts are still available from the early 90s when the mags were printed.

thanks for any advice!
Don't get duped into believing you'll achieve over 425H/P w/ some of your air system upgrades. They R&D these systems out of the car w/ Long tubes, no a/c and the whole 9 yards. I was led to believe that whenever I purchased my system. I bought a zz9 cam, GM Fast Heads, 1.5/1.6 rockers, 58mm BBk Throttle body, thinner head gasket for better compression, SLP air induction w/ K&N filter, and a Mini-Ram 111-the best dyno time I received was mid 250 at the rear wheels and 348 w/ a 125 shot, Hooker shorties and a FloMaster Series 80 3" exhaust. The times i received I was told by my Tuner man, these times are close to your LT1 stock #s. Now, w/ a more aggressive cam and long tubes and no cats should boost your numbers, if you can handle the noise. Good Luck on your Quest! I'll post my new numbers whenever I get them-I'm also running Royal Purple throughout my 88.
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Old 07-11-2006   #9
strc09
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Re: suggested mods - 400 HP from 1989 L98

What kind of long tubes do you reccommend for our cars? Also, how will that effect the exhaust system?
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GTA: Grand Turismo Americano (Grand Touring America)
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Old 07-11-2006   #10
Klortho
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Re: suggested mods - 400 HP from 1989 L98

I was being sarcastic about the 200 shot, however I do have a buddy who ran a 175 shot on a stock LT1.

It's going to be really really hard to get 400 rwhp with a L98. I'm hoping for mid 13's with a stock LT1 (low 8's in the 1/8th) and I know this is possible since I've seen a timeslip from a stock LT1 in a 3rd gen camaro ran like 13.8 spinning through first and second on street tires, with drag radials we both think low 13's maybe high 12's.
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Old 07-11-2006   #11
Fred91GTA
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Re: suggested mods - 400 HP from 1989 L98

Well, I seriously doubt you can get 400rwhp from an L98, but over 400 flywheel horsepower is definitely attainable. I've done it. Here's my engine setup:

SLP T-RAM intake manifold
SLP Tri-Y headers,
SLP Cold Air kit
SLP catback exhaust
Comp Cams XE276HR-12 cam
AFR 195 Heads milled to 58cc
10.5:1 compression
Accel 26# injectors
Walbro 255 fuel pump
MSD everything on ignition
Custom tuned chip for the mods

The engine still has the stock shortblock with 52k miles on it. I put down about 360rwhp on my last dyno session. Coupled with the Vigilante Stall and TransGo Shift kit, the engine is an animal from idle to redline.

BUT, the tranny's dying... go figure.

I'm planning a similar setup for my black GTA. Yes... I have two T-RAMs...
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Old 07-11-2006   #12
Fred91GTA
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Re: suggested mods - 400 HP from 1989 L98

Oh yeah, almost forgot. Don't forget the subframe conenctors and the suspension mods. With the motor making that much power, the torque is going to rip your car apart.
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Old 07-15-2006   #13
Black88gta
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Re: suggested mods - 400 HP from 1989 L98

Could you post a pic of the t-ram, I don't think i've ever seen one.
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Old 07-15-2006   #14
Fred91GTA
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Re: suggested mods - 400 HP from 1989 L98

Quote:
Originally Posted by Black88gta
Could you post a pic of the t-ram, I don't think i've ever seen one.

Here's a link to my cardomain page:

http://www.cardomain.com/id/spectre91gta

The pics of the T-RAM are on pages 5 and 6.
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Old 07-16-2006   #15
MunsonGTA
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Re: suggested mods - 400 HP from 1989 L98

Quote:
Originally Posted by Klortho
I was being sarcastic about the 200 shot, however I do have a buddy who ran a 175 shot on a stock LT1.

It's going to be really really hard to get 400 rwhp with a L98. I'm hoping for mid 13's with a stock LT1 (low 8's in the 1/8th) and I know this is possible since I've seen a timeslip from a stock LT1 in a 3rd gen camaro ran like 13.8 spinning through first and second on street tires, with drag radials we both think low 13's maybe high 12's.
he never said he wanted 400 rwhp. he said he wanted high 12's to low 13's, which is easy for an L98 motor. All it takes is some traction and a little power. Pretty much if you get 300 rwhp to the ground, or atleast somewhat to the ground, you'll hit low 13's. And you can build a faster L98 motor with the cash it would take to swap in an lt1 or ls1.
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11.16 at 123 mph.
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Old 07-16-2006   #16
Klortho
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Re: suggested mods - 400 HP from 1989 L98

It's in his title of the thread

400 HP from 1989 L98

And I guarantee I have less in my LT1 swap than people has in L98's getting the car to run low 13's. And the LT1 probably has close to 260 or so to the wheels.
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Old 07-16-2006   #17
FearThisGTA
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Re: suggested mods - 400 HP from 1989 L98

400 is not a problem form an L98, it just depends on your set up and induction.
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Time of Death on motor, 4:07pm on 05/29/2010.
Hp:211.2@4200rpms/Tq.328.5@2700rpms
Best et: 13.959@97.05mph
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Old 07-16-2006   #18
Fred91GTA
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Re: suggested mods - 400 HP from 1989 L98

Want the easiest way to get 400 HP from a stock L98? Get all the bolt ons possible. Port your plenum and get large runners.

THEN, run a rear mount turbo setup at 9psi. It's the easiest setup I've ever worked with. We just finished a rear mount turbo setup for my cousin's 92 Z28. Did all the piping ourselves. Total cost? $800 bucks. This included a rebuilt T-4 Turbo.

And it hauls some major ***
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Old 07-17-2006   #19
MunsonGTA
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Re: suggested mods - 400 HP from 1989 L98

Quote:
Originally Posted by Klortho
It's in his title of the thread

400 HP from 1989 L98

And I guarantee I have less in my LT1 swap than people has in L98's getting the car to run low 13's. And the LT1 probably has close to 260 or so to the wheels.
the title says 400 hp, not 400 rwhp. how much did the lt1 swap cost you?
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11.16 at 123 mph.
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Old 07-17-2006   #20
torqueaddict
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Re: suggested mods - 400 HP from 1989 L98

Thanks for all the responses. I did mean engine hp, not rwhp. I've been considering forced induction as a starting point and seeing where I'm at then. It just seems the easiest way to get a lot of hp without taking apart the motor. I'm curious about that turbo kit someone mentioned. I can only find superchargers for my car (ATI, Paxton) I know the supercharger may cost 3000+ but I can spend that on good headers, intake, cam, and head work.

I tried to get the subframe braces on my car this weekend, but apparently they don't fit with the dual cat option (without at least removing them for the installation- and maybe customizing the exhaust) I picked them up at Carlisle- I think the company was UCI or something like that.
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