Advice on performance mods
Thread Starter
Team Owner
Joined: Sep 2002
Posts: 22,209
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From: OBAMA IS HITLER
Advice on performance mods
I am new to owning a corvette and am a dummie regarding engine/exhaust modifications. I have a 1990 6 speed, 3.33 rear end gear.
Everything is stock. I would love to know a couple mods that might improve the low end and hopefully somewhat in the high end (if possible)....ones that are both the cheapest, easiest and/or have the most impact for the $$. What improvements can be made for approx. $1K and under? Performance 101 for the beginner! :D
Everything is stock. I would love to know a couple mods that might improve the low end and hopefully somewhat in the high end (if possible)....ones that are both the cheapest, easiest and/or have the most impact for the $$. What improvements can be made for approx. $1K and under? Performance 101 for the beginner! :D
Team Owner
Joined: Nov 1999
Posts: 26,679
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From: This vette goes to 11 Milford MA
St. Jude Donor '03-'05
Re: Advice on performance mods (bradvette)
You have what will be referred to here as an "L98".
First off, tune it with quality parts.
Seconds-FREE MODS.
Cut the air lid, add a good filter, remove the MAF screens, remove the frisbee, bypass the throttle body hoses, add a lower thermostat.
Next, exhaust. A good set of headers and a decent exhaust REALLY wakes up the L98. After that, its time for intake manifold ugrades, as the TPI noses BAD after 4500 RPM's. Do a search, all of these mods here are covered.
First off, tune it with quality parts.
Seconds-FREE MODS.
Cut the air lid, add a good filter, remove the MAF screens, remove the frisbee, bypass the throttle body hoses, add a lower thermostat.
Next, exhaust. A good set of headers and a decent exhaust REALLY wakes up the L98. After that, its time for intake manifold ugrades, as the TPI noses BAD after 4500 RPM's. Do a search, all of these mods here are covered.
Thread Starter
Team Owner
Joined: Sep 2002
Posts: 22,209
Likes: 12
From: OBAMA IS HITLER
Re: Advice on performance mods (Fastguy)
Oh yews, I forgot to ask.....what kind of HP gains can by typically expected with each of the modifications that were listed above? Reason I ask is that I'm not looking to race anything, just trying to get a bang ofr the buck in terms of everyday pick-up-and-go driving. Where is a good source of info to perform the modifications? (I'm not all that savvy when it comes to mechanics) How about typical cost/time associated with each? Thanks for your consideration, this is a great Forum and place to be!
Team Owner
Joined: Sep 2001
Posts: 62,137
Likes: 1,727
From: Athens AL
C7 of the Year - Unmodified Finalist 2021
C4 of Year Finalist (performance mods) 2019
Re: Advice on performance mods (Fastguy)
On the L98, the K&N w/ open lid is worth ~5hp (filter is $50, time for me was an hour or so)
Frisbee is about 10hp (my car didnt come with it)
TB bypass and MAF screen removal are together worth around 5hp (i havent done the MAF screen thing, but the bypass is just removing the two coolant hoses from the TB and mating them together with a piece of pipe and 2 clamps)
But Longtube headers are worth 15hp, and catback is usually worth 10hp. Headers cost from $500-800, exhaust $500-900 (depends on brand)
Frisbee is about 10hp (my car didnt come with it)
TB bypass and MAF screen removal are together worth around 5hp (i havent done the MAF screen thing, but the bypass is just removing the two coolant hoses from the TB and mating them together with a piece of pipe and 2 clamps)
But Longtube headers are worth 15hp, and catback is usually worth 10hp. Headers cost from $500-800, exhaust $500-900 (depends on brand)
Burning Brakes
Joined: Jan 2001
Posts: 1,169
Likes: 0
From: Manhattan
Re: Advice on performance mods (bradvette)
Welcome :seeya
first off, you don't have a MAF, so you can't remove the screens. our cars are Speed Density, they use a pressure sensor in the intake manifold. My first mods were a good tune up, i was trying to track down an intermittant low power problem, including cap, rotor, coil, ignition module, spark plugs, wires and a K&N.
The next step was removing the AIR pump with the AIR Eliminator Kit (~$180) and installing long tube headers, true dual exhaust w/ no cats, removing the frisbee and bypassing the coolant from the throtle body. This gave me 40hp and 30 tq at the wheels.
my suggestion on the exhaust: if i were to do it over, i'd get the hooker supercomps over the headmans (about twice the price, you *have* to coat the headmans) and get a local exhaust place to bend the pipes. Also, the later C4's (92-96) came with true duals. you can buy all the hangers from Jeff Kopp (18carfan). I have a list of all the parts for the hanges, let me know if your interested and i'll mail 'em over.
first off, you don't have a MAF, so you can't remove the screens. our cars are Speed Density, they use a pressure sensor in the intake manifold. My first mods were a good tune up, i was trying to track down an intermittant low power problem, including cap, rotor, coil, ignition module, spark plugs, wires and a K&N.
The next step was removing the AIR pump with the AIR Eliminator Kit (~$180) and installing long tube headers, true dual exhaust w/ no cats, removing the frisbee and bypassing the coolant from the throtle body. This gave me 40hp and 30 tq at the wheels.
my suggestion on the exhaust: if i were to do it over, i'd get the hooker supercomps over the headmans (about twice the price, you *have* to coat the headmans) and get a local exhaust place to bend the pipes. Also, the later C4's (92-96) came with true duals. you can buy all the hangers from Jeff Kopp (18carfan). I have a list of all the parts for the hanges, let me know if your interested and i'll mail 'em over.
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Burning Brakes
Joined: Jan 2001
Posts: 1,169
Likes: 0
From: Manhattan
Re: Advice on performance mods (BIG JIM 54)
it's a metal disk, about 10 inches diameter, bolted to the crank pully, supposedly put there to dampen any vibrations that might occur when the a/c cycles on and off. it's not on all L98's and everyone who's posted about removing theirs has reported no adverse effects.
Melting Slicks
Joined: Aug 2000
Posts: 2,009
Likes: 1
From: Springfield MO
Re: Advice on performance mods (Raistlin)
I too have a 90 and my mods and results are in my signature. I would first cut the air lid (above the air filter) and bypass the coolant lines that flow through the throttle body (heating the air charge...we all know cooler air is better) These won't cost anything but time. Next I would break open your wallet and order either a set of TPIS coated headers (700 bones) or the TPIS catback 600 (bones)....all from tpis.com. I understand your budget and either of the two will present you with a power gain and leave you satisfied with the results. While your under the car installing either the headers or the catback I would next punch out the main catyletic convertor (another free mod that will give you seat of the pants performance and give your car a different tone). You could also order a crank pulley and new serpatine belt for 100 through ASP (good for a tenth or so) These will certainly open your L98, good luck and if you have any more ?'s the forum is a great place to ask!
Burning Brakes
Joined: Apr 2002
Posts: 755
Likes: 0
From: Patterson CA
Re: Advice on performance mods (bradvette)
:cheers: Welcome to the Forum and your new addiction! :cheers:
One of the most important things to remember about owning a Vet is: DON'T FORGET TO WAVE!!! :seeya
One of the most important things to remember about owning a Vet is: DON'T FORGET TO WAVE!!! :seeya
Team Owner
Joined: Dec 2000
Posts: 90,675
Likes: 304
From: SE NY
Cruise-In II Veteran
Re: Advice on performance mods (bradvette)
Congrats on your new '90 Vette and welcome to the Forum.
The guys have listed most of the simple mods and exhaust mods.
In addition I would suggest a HyperTech coil/cap/rotor, TPIS wires and AC Delco cut-back (details on my site) plugs for about 10hp gain.
You may be able to advance base timing for better throttle response and maybe some additional HP but realy need a scan tool to check for knock counts, which would detract from performance.
Adding an Adjustable Fuel Pressure Regulator (AFPR) will allow you to tune fuel flow to increased air flow. This will work with your Speed Density (SD) setup till you make mods (like a cam change) that effect manifold vacuum.
If you do a 2 1/2" front Y-pipe, hi-flow cat and muffler elims along with the mentioned mods you can likely come in close to your current budget goals.
I'm sending you e-mail with results of some other mods to a '90 Vette 6-speed. This is to tantelize you for the next phase of the never ending quest for "more power". :D
The guys have listed most of the simple mods and exhaust mods.
In addition I would suggest a HyperTech coil/cap/rotor, TPIS wires and AC Delco cut-back (details on my site) plugs for about 10hp gain.
You may be able to advance base timing for better throttle response and maybe some additional HP but realy need a scan tool to check for knock counts, which would detract from performance.
Adding an Adjustable Fuel Pressure Regulator (AFPR) will allow you to tune fuel flow to increased air flow. This will work with your Speed Density (SD) setup till you make mods (like a cam change) that effect manifold vacuum.
If you do a 2 1/2" front Y-pipe, hi-flow cat and muffler elims along with the mentioned mods you can likely come in close to your current budget goals.
I'm sending you e-mail with results of some other mods to a '90 Vette 6-speed. This is to tantelize you for the next phase of the never ending quest for "more power". :D
Thread Starter
Team Owner
Joined: Sep 2002
Posts: 22,209
Likes: 12
From: OBAMA IS HITLER
Re: Advice on performance mods (65Z01)
Wow, thanks everybody for all the great responses. Looks like one thing at a time. I'm a real novice at anything performance, plus my vette is the 1rst real car I ever owned. By the way, "punching out" a catalytic converter - wouldn't that cause issues when the next inspection comes around? I thought they were mandatory. Please excuse me for my ignorance, like I said I'm totally new to all this and need all the help I can get! :jester
Instructor
Joined: Aug 2002
Posts: 141
Likes: 12
From: Saint joseph MI
Re: Advice on performance mods (65Z01)
Bradvette,
Please send me the email with '90, 6 spd mods, as I have a bone stock 90, 6spd, vert that I"m about to base line up at Indy.
Jeff
jhughes@hsonline.net
Please send me the email with '90, 6 spd mods, as I have a bone stock 90, 6spd, vert that I"m about to base line up at Indy.
Jeff
jhughes@hsonline.net
Burning Brakes
Joined: Jan 2001
Posts: 1,169
Likes: 0
From: Manhattan
Re: Advice on performance mods (bradvette)
Wow, thanks everybody for all the great responses. Looks like one thing at a time. I'm a real novice at anything performance, plus my vette is the 1rst real car I ever owned. By the way, "punching out" a catalytic converter - wouldn't that cause issues when the next inspection comes around? I thought they were mandatory. Please excuse me for my ignorance, like I said I'm totally new to all this and need all the help I can get! :jester
Racer
Joined: Aug 2002
Posts: 432
Likes: 0
From: Lancaster CA
Re: Advice on performance mods (spineshank)
DON"T hollow out your cat! this will only cause turbulence, and hurt your exhaust flow. if you dont want cats then have a test pipe installed. then you have your straight through flw and you can put your cats back on for smog time. :seeya :chevy :seeya