tossing the cats and dumpin the pipes, would that be a bad idea?
89 vette performance ?
Thread Starter
Instructor
Joined: Jun 2008
Posts: 156
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From: St. Louis
89 vette performance ?
hey guys im new to the forum and was just wondering what would be good mods to start with. the car is completely stock to my knowledge has the L98 tpi. i just bought the car 2 days ago with 214xxx for 3500..thanks alot
Le Mans Master
Joined: Jun 2006
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From: One day you're a Comet...the next day you're dust... Arkansas
Team Owner
Joined: Dec 2000
Posts: 90,675
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From: SE NY
Cruise-In II Veteran
...what would be good mods to start with. the car is completely stock to my knowledge ...
-toss the frisbee disc from the front of the WP pulley
-cut air filter lid with or without K&N
-160deg T-stat & fan switch
-toss the spare & jack
The L98 exhaust system is a place where some real HP gains can be had, though not by any streatch cheaply. The most efficient (IMO) exhaust has:
-FL coated headers
-mandrel bent 2 1/2" to 3" dia tubing
-X-pipe in front of dual hi-flow cats
-hi-flow mufflers
BTW, welcome to the Forum and congrats on your new '89 Vette...
Last edited by 65Z01; Jun 27, 2008 at 10:34 PM.
Racer
Joined: Jun 2006
Posts: 477
Likes: 1
From: Jefferson Georgia
I installed a complete exhaust for my 88 from corvette central, magniflow, no cats, man what a difference. 187000 miles and with all the free mods, a rebuilt tranny with 2500 stall and a few tricks/mods of my own I have no problem hangin with a c6. C6 owners just don't understand that these C4s stick like glue and are easy/inexpensive to hot rod. Yeah, I know the tpi chokes out about 4500 but that low end torque is a rush.
Former Vendor
Joined: Nov 2006
Posts: 2,482
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From: Carmichael ca
Some good advice so far. Definitely check the compression before doing anything. If that's OK, check all your basic tune up stuff like cap, rotor, plug wires, plugs, air and fuel filter. Replace anything that looks old. I would also check timing and fuel pressure.
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Race Director
Joined: Nov 2003
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From: Overland Park Kansas
2020 Corvette of the Year Finalist (appearance mods)
C4 of Year Winner (appearance mods) 2019
Look at the universal Magnaflow cats. High flowing....
Do install an X pipe.
Melting Slicks
Joined: Jan 2008
Posts: 2,065
Likes: 1
From: Jasper Texas
Alot of people around here support balance tubes and high flow cats. I went cheap, long tubes to true dual 3" back to the rear, then 2 1/2" to the mufflers (flowmaster 40s).
Heres a sound clip for you, the engine isn't exactly stock, but it'll give you some idea of what a true dual setup may sound like.
http://s273.photobucket.com/albums/j...t=100_0621.flv
Heres a sound clip for you, the engine isn't exactly stock, but it'll give you some idea of what a true dual setup may sound like.
http://s273.photobucket.com/albums/j...t=100_0621.flv
Melting Slicks
Joined: Jan 2008
Posts: 2,065
Likes: 1
From: Jasper Texas
I installed a complete exhaust for my 88 from corvette central, magniflow, no cats, man what a difference. 187000 miles and with all the free mods, a rebuilt tranny with 2500 stall and a few tricks/mods of my own I have no problem hangin with a c6. C6 owners just don't understand that these C4s stick like glue and are easy/inexpensive to hot rod. Yeah, I know the tpi chokes out about 4500 but that low end torque is a rush.
Race Director
Joined: Nov 2003
Posts: 12,221
Likes: 446
From: Overland Park Kansas
2020 Corvette of the Year Finalist (appearance mods)
C4 of Year Winner (appearance mods) 2019
$33,000 when it was new. So you bought it at 1/10th the price! 
Or did you mean HP? or torque? OR HEAD FLOW? or skid pad G force? Or recommended tire pressure?
245HP, 350TQ.
Or did you mean HP? or torque? OR HEAD FLOW? or skid pad G force? Or recommended tire pressure?
245HP, 350TQ.
Le Mans Master
Joined: Jun 2006
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From: One day you're a Comet...the next day you're dust... Arkansas
Drifting
Joined: Sep 2002
Posts: 1,642
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From: Suwanee,Ga
Drive it a while, and if it has not been wrecked, is reasonably straight, you have a good starting point.
C4 is a great platform and there is a world of stuff out there to make enough power to create something that just barely makes a bad airplane.
Remember With Great Power comes a Small bank account.
Though I think LT1 might be a mistake. It's not just a motor swap.
TJM
Team Owner
Joined: Feb 2006
Posts: 24,460
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From: sw Ohio
With that kind of mileage I see two options, drive it around like a DD. Or if you want performance i'd yank the engine out and rebuild it now because its not going to last too long hot rodding it if its never been rebuilt. Maybe i'm just using the mileage as an excuse but thats what i'd do.
Pro
Joined: Jan 2008
Posts: 584
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From: Near Lockport NY Black 1986 Coupe
With that kind of mileage I see two options, drive it around like a DD. Or if you want performance i'd yank the engine out and rebuild it now because its not going to last too long hot rodding it if its never been rebuilt. Maybe i'm just using the mileage as an excuse but thats what i'd do.
Rebuild it or start fresh with a crate, as some problems with these high mileage motors may cost you more to fix it than it would for a brand new motor. You usually get the best bang for the buck if you have others build a motor and buy it off of them, compared to buying it all yourself - unless you do the labor.
Once you figure out how the motor will be fixed, or checked anyway, work on the exhaust. L98s can't flow junk for cfm through those restrictive pipes. Get rid of the pre-cats, and get a high-flow cat or gut it and keep a pipe in the middle so it flows straight through. Or you can get LT headers and run duals straight back with an X-pipe. Throw on a set of muffler eliminators for rumble, or performance mufflers for tone. Either way to build up the exhaust will give you around 40-50 flbs. of torque and ~20-30rwhp to play with.
After that, you have to dig deep into your pockets for work on the intake, heads, and cam. Oh, and congrats on the new ride.
