ZBrink

This is an 89' coupe with a 3.07 rearend and automatic transmission. It has 57k on the odometer. It is bone stock with factory intake and exhaust. I do not want to switch out the heads and cam so please do not suggest this. I also don't want to sacrifice gas mileage because my girlfriend drives this one. She also doesn't like it loud. Other than that I am very open to suggestions. I know I'm not going to pump an extra 150ph!! out without major mods but the car needs to do a little better in areas like throttle response, weaving through traffic, and passing. I see all these little things like airfoils, aftermarket spark plug wires, new/modified MAFs, ported intake runners, chips, intakes ets. What are some good mods and brands that actually work? Thanks!
Zack

borderchris

Sounds like a great car. First off, don't blow your change on an airfoil. Take the $50+ and buy a K+N filter instead. For the L-98, Magnaflow makes a gorgeous cat-back, all stainless steel system that is perfect (great performance, but not too dukes-of-hazzard on the sound) for the car.

Beyond that, I would first look at a really quality tune-up. This is where people are LOSING power, and not even knowing it. Quality plugs, PCV valve, cap, rotor, 8MM wires and ignition module are huge. Make sure your throttle position sensor is set properly, and that your fuel filter is clean. If you're looking to spend a little dough, get some shorter gears. Don't bother with a chip- they don't do much on these cars. As far as real money goes, there are a couple of great supercharger kits out there, as well as much improved TPI intake and rail set-ups (Accel is good). Good luck!

Chris

scorp508

Longtube headers are one of the best things you can do for an L98.

stevec4

Put simply, the L98 suffers from relatively poor airflow in and out of the engine and so the best mods are those that address these issues. However by making any changes you risk creating more noise.

The mods in order of cost and complexity are discussed throughout the forum and personally I am working through the following list on my 88

1. K&N Air Filter with cut lid
2. Airfoil (jury is out as to whether it works but it makes me feel better LOL)
3. Exhaust system - mine is cat back ANSA with rear mufflers removed - nice sounds.
4. Bosch Platinum+4 plugs and new MSD wires (lots of arguments about whether they work or not on the Forum - I think they do, lots think they don't)
5. Descreen the MAF (no other car I have had has ever had sceens to I'm gambling that it don't hurt)
6. Remove the damper disk from the front of the engine.

After that you get into trick manifolds, large tube runners, ported plenum, bigger throttle housing and long tube headers - that needs to be done as a package and is kinda expensive and a fair bit of downtime with the vehicle. Plus if you are doing that then you might was well do the heads and cam.

Just me thoughts and my plan of campaign - 1-5 have already been done. 6 is for the weekend.

vader86

If you want any power gains without heads/cam, it'll require exhaust from the headers back and larger runners/ported plenum.

Most of the stuff in the magazines is junk, so dont believe their power gains. Especially the airfoil.

ZBrink

What are some good LT headers for this car? I would like to keep the main cats but the pups can go.

vader86

TPiS or Hooker 2149 headers would be the way to go.

scorp508

The "big 3" are.... Hooker, TPiS, and Lingenfelter.

I run the Hooker 2149 on my own car. They are 1.75" primaries, 3" collectors, and have all emissions hookups.

65Z01

If you do FL headers and a hi-flow main cat maybe Power Effects would be a good cat-back. It is adjustable for quiet or open as you like.

Consider also a low temp T-stat & fan switch.

If you do full exhaust, air filter, intake, T-stat mods and toss the frisbee you should be looking at a little over 300hp.

TIMSPEED

You have an 89, so you're already starting out good..
1.) GM 2025rpm stall Converter (Commonly reffered to as the "S10" Converter
This won't give you any additional power, but it will put better use to the power you DO have, therefore making it faster. (Read: More efficient)
2.) Have your Pre-Cats/Mufflers replaced with straight piping. When you do this, be sure to replace your main cat with a high flow unit (Carsound/Magnaflow is my personal choice)
3.) Bump the timing up to 8deg
4.) Install a K&N Air Filter, along with cutting the AirLid open.
5.) Make sure your car has a fresh tune up/fluids. Although it's not necessary to go with aftermarket HEI parts, I feel, if you're going to replace your stock stuff, might as well get better than stock, which is why I recommend getting the Hypertech Power Coil Kit.
With those five things, I can gurantee it'll feel like a whole different car

88BlackZ-51

LT'S, I did Hooker 2149's. They sound and perform good, and to mention look way better then the 1 5/8 little guys.

formul89

I would recommend the "airfoil" if you can find someone selling one cheap. Every little bit does help!

I would also recommend doing a thorough cleaning of the throttle body to remove gunk, reset the IAC and TPS. Alsom remove the plenum and grind down the walls on the intake holes. There is plenty of info on this here.

All these little things add up to some cheap HP. It is not really adding any HP, just freeing up some HP.

I have done all these mods except the plenum porting and it runs strong.

vette-rookie

It sounds like what your asking for is a set of lower gears. The car probably has enough power for passing ect, just needs a little more gear to let you do it faster. that wont change the looks or sound and MPG isnt that different.

vette&f-bod lover

a few years ago,these are the mods I used on my 90 to get it into the low 13's without touching the motor.

AC rapid fire plugs
Livewire sparkplug wires
Davis coil,cap,&rotor
K&N air filter/modified air lid
AC 160 thermostat
TPIS stage 2 chip
adjustable fuel pressure regulator(49 PSI)
Large tube runners
ported plenum
airfoil
1 3/4 headers
random cat
Flowmaster catback
Richmond 3.54 gears
2600 torque converter(I think continental)
transgo shift kit
BFG 275 dragradials

mods I felt the most were in order
1.gears(I had 2.59's)
2.torque converter/shift kit
3.headers/catback
4.chip/air intake

you already have the 3.07's,so I wouldnt be in a rush to (or even)change them.after you have everything tuned,I would start with a higher stall torque converter/shift kit combo,then headers/catback,then chip & air intake.dont forget a good set of DR's so you can get SOME of that L98 torque to the ground

cmashark

what are you talking about? i am drawing a blank and the only thing that comes to mind is the harmonic balancer and hopefully you are not refering to this. clue me in.

chris

cv67

There are 4 bolts on the front of the water pumpr pulley. You will see the large disc, known around here as a "frisbee". It helps, only takes a few minutes to remove. You wouldn't believe how heavy they really are.

If you want the exhaust to flow well and remain quiet, throw a set of LT1 Mufflers and tips on. Some guys here practically give them away. Check the C4 parts for sale section.
1.6 rockers/springs kick the power up a notch, too.

vettefun

Hey Zbrink....

I'm pretty much in your same boat with a stock C4. I've been doing "A LOT" of research on mods myself and everybody is pretty much dead on. First place to start is with the breathing issue. You got to get the air in and the air out, intake & exhaust. Get a good tune-up first so you have a good base point and do those free mods mentioned. You got some "decent" gears for now, just work a little more on the flow, she'll wake up!!!!!!

65Z01 has good tips on his site for these L98's, most are free or almost free and he really knows his stuff (Thanks Jim!)

http://www.geocities.com/jgkov/index.html

Mad-Mic

with a hand full of mods i turned a 13.18@105.88 mph with a 1.815 60' with stock 1600 stall, stock tranny, stock 2.59 gears, stock motor from TB to Oil Pan.

only mods at the time were:
K&N open air box, MAF descreened, TB Bypassed, 160* T-Stat, Accel Super Coil, 12* degree advance timing, AC Delco Rapid Fire plugs gapped at .047 Indexed, TPiS Long Tube Headers, !Air, !Cat, !EGR with rear Dumps off the rear Y pipe. Hayden Tranny cooler. Stock 1600 rpm stall, 2.59 rear gear on 285/40/17" Goodyear F1 D3's set at 18.5 psi.

never got a clean run on the next mods i did.
BFG DR's, Air Elim Pulley, Crank Pulley, and Cut Back AC Delco Rapid Fires. I also added Chambered Muffler Eliminators with LT1 Tips. I still have an AFPR to put in and relocate the MAT sensor. i think that is good for solid 12's in good air.

formul89

105mph trap speed with a stock top end TPI? Hmmm....I had larger manifold, AS&M LTR's, and other basic mods and hit 100mph tops in my '89 Formula 350 .

Sounds interesting...

sami85L98

My friend why not u go for this complete thing plus exhaust setup and u r done:

Tpis 300-203 Includes all this for $3750:

Big mouth base, LT runners, ported plenum (ur's), 52mm TB (ur's),
Fuel pump, Custom wire harness, all relays, new ECU with Level iv chip,
New Bosch injectors , new TPS, Knock Sensor,
O2 with bung, IAC, TPIS AFPR, Air foil, Distributor and cap.

Than followed by Hooker headers or Tpis coated $520/750,
Hooker y pipe 165, Random hi flo cat, ur choice of Mufflers or cat back
all perform same except noise how about flow master 50 series not really loud its a mild aggressive sweet sound.

After this u r over 100 hp and feel the power at all RPM level.

Tpis r experienced people and know thier stuff and thier level Iv prom
is sure a delight i got thier level V prom after adding cam/head too
i see the power power power ........... power.

If still money is left go for 2400 stall converter and transgo shift kit.
oh forgot the K & N cut filter lid.


Good luck sami.