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Stock L98 upgrade

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Old 03-02-2001, 04:02 PM   #1
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Stock L98 upgrade

I have a stock '89 L98 engine and I want to get about 400hp out of it and still use as a daily driver. I'll get the heads(cast iron) ported, upgrade exhaust, upgrade intake (super, mini ram or accel runners?), custom chip, and was wondering what cam to use. Like to do cheapest way besides nos, power adders, or carb. Any suggestions?
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Old 03-03-2001, 12:57 AM   #2
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If your intake and heads flow well, get the LT4 HOT Cam or the ZZ4 Cam from GMPP. I got my LT4 HOT Cam for $184 with shipping from

1987 Chevy Camaro IROC-Z
L98 TPI 350 (5.7L)
TH 700R-4 Transmission
Borg Warner 7.75" 9 Bolt Rear End

Current Mods: LT4 Hot Cam, Comp Cams 1.52:1 Roller Rocker Arms, Edelbrock TES 1 5/8" Headers, Hooker 3" Aerochamber Cat-Back System, Performance Resource Chip, Accel Ignition Coil, Cap, Rotor, 8.8mm Wires, K&N Filters, JET TPI Air Foil, All Free Mods, Falken ZIEX Z-Rated Tires.

Best ET (w/o LT4 cam): 14.32 @ 97.7mph
(corrected for elevation)

7.5" 10 Bolt with 3.42s soon to come!
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Old 03-03-2001, 01:36 AM   #3
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Location: Kempner,TX,
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Car: 1996 Vette / 1992 GSX1100F Suzuki
Engine: 1996 Corvette Coupe 388 LT1 (+.060)
Transmission: Auto
Axle/Gears: 3.07

That's a tall order, if you're talking rear wheel HP.

Getting 400 HP at the rear wheels from a 350 TPI engine MAY be doable, but, MAN, does it call for a lot of mods. Keeping it as a daily driver makes it just about impossible.

There are guys who are running 383s and 396s still trying to get that magic number at the rear wheels. You're talking close to 1.15 HP per cubic inch. That's an awful lot.

In order to do it you've got to remove all the L 98s flow restrictions and you'll have to rev the engine a lot higher than the stock redline; at least by 1000 RPMs. The easiest ways to increased power are to make the engine bigger or rev it higher.

You'll need a complete intake do-over by going with a MiniRam, TPIS's fuel rails, better fuel pump;

Full length headers will no or high flowing CATs and mufflers;

New camshaft; perhaps the CompCams 224/230 hydraulic roller;

1.6 Roller rockers

Air Flow Research 190 aluminum heads. Ported, stock heads won't flow nearly enough.

Vigilante converter

Higher compression; meaning new pistons with plasma moly rings.


Getting that much from a stock short block, I believe is going to be a tremendous strain on the cast crank and two bolt block, not to mention the stock pistons if you opt to stick with those.

I'd lower my sights a little. Shoot for one HP per cubic inch in a daily driver. That's more realistic.

I've seen ads about 400 HP engines (which ads I take with a grain of salt), but I'll bet that's crank HP not at the rear wheels. To get 400 HP at the rear wheels, you'd need close to 500 HP at the crank.

Maybe someone else can chime in and give us all the magic receipe.

Just my thoughts.


1986 Corvette Coupe, 415 CID, Edelbrock 6073s, ZZ9
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Old 03-03-2001, 02:03 AM   #4
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Car: Red 87 IROC-Z28 T-Top
Engine: 5.7 Tuned Port Injection
Transmission: 700R4 Auto
Axle/Gears: BW 9-Bolt 3.27

Why do u want 400HP?? What times do u want to run??

Looking For:

87 IROC-Z 350 TPI
84 TRANS AM 305 H.O.
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Old 03-03-2001, 10:48 AM   #5
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Location: Cincinnati,Ohio
Posts: 1,453
Car: 1991 BandittII Firebird
Engine: 5.7 Tune Port Injection
Transmission: 700R4
Axle/Gears: 3.27 9 bolt

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