i am wanting to get my stock L98 1988 GTA up to around 300 horsepower, but im not sure what i should do to get it there. There are many options but i dont have alot of money to spend.

I dont want to go very deep in the engine, i currently have all the TPI stuff off all the way down to the lower intake because i'm putting on SLP runners. but what else should i do? should i go ahead and replace the injectors while i already have everything apart? what about a fuel pressure regulator?

other mods i have in mind include 3.73's, some type of chip, and headers.

any other suggestions? if there is a more money efficient way to achieve my goal of 300 horsepower i would love to hear it.

thanks
kyle

 

first thing is first you will need a tune up, replace plugs wires dist cap and rotor. Then you can Port the plenum, headers, low restriction exhaust, low restriction cat (when needed) 1.6 rockers, high flow air filter, fp regulator and a custom prom. That should do it! Gears are not going to add any horsepower.. Or you could skip everything mentioned above and get a nitrous kit.

 

Aside from nitrous, start with a good set of headers and free flowing exhaust if you didnt already. Then toss a cam in and retune.

 

the tune-up has been done. i am working on the plenum/ runners right now. should i mess with taking off the intake and porting it?

headers will hopefully come but i need to get some of the crap in the engine bay out of the way first. im not real sure on how to go about doing that though. like the little box with all the hoses running into it and is located right above that passenger side valve cover. i already have a catback.

 

Are you talking 300 wheel horsepower or 300 engine horsepower? I think at the engine all the bolt ons will get you there. But wheel hp you will need a cam or nitrous at least.

 

yeah i didnt figure it would get me quite 300 at the wheels but i really just want to give the car some extra power without spending lots of money or getting way into the engine.

 

stock 87 L98 with vortec heads, and scoggin dickey vortec TPI base.... stock everything else and you got 305hp... i memorized the article.

add... runners, TB, gm hot cam, 1.6rr. port plenum and u got 354hp, 432tq. good 3" exhuast wit headers and expect more hp/tq along with a custom burn chip.... thats the cheapest i would do and u would be satisfied

 

holly stealth ram dont bother proting teh stock tpi set up.. the stealth ram works soo much better and isnt "too" expensive aside from that port ur heads throw a cam n chip like everyone else has said and you might get 300-320 horse and get 4.10 gears (unless its a daily driver then 3.73) so u can move that power to teh wheels better... also a higher stall converter for better low end

 

i dont know guys, you're getting into some expensive stuff. im looking at spending a grand at max. and i want to get a good base, so i have to do headers, which will be about $300 , so i got maybe 700 more to work with. i already have the SLP runners and porting the rest of the intake wont cost much. but i have no experience with cam installations so that would have to be done for me and i would assume that would be quite expensive. what would a cam installation run price wise? and getting heads ported...whats that cost?

 

if you got SLP runners, then use them. take off the manifold and port it...siamese it too about an inch or 1.5". port the plenum out, match the runners to the plenum and base.

You will need some header/ypipe setup or custom exhaust. shortie headers and good 3inch exhaust will give you the biggest bang for the buck.

Then get a chip made, it be best to do it yourself... all you want to do with a custom chip is to run a more aggressive timing curve. bring in max timing sooner at like 3000 rpms. then possibly taper it off after 4800 1 degree. I'd run 34-35 degrees and see how it responds. Also give it 2-3 degrees advance all around. You wont need to mess with fuel curves, just use a fuel pressure regulator...turn it up to about 46psi. that will let that motor breathe well to 5000rpms.

If you can find someone to do that for cheap or dont wanna get into it yourself just yet, then just run advance on the distributor. set your base timing to 8-10 degrees and be set. my car liked 8. When i got the chip burning stuff, i was able to fine tune the timing curve for all rpms and get abit more torque and hp out of it

It will make as much power as a HSR intake i'm willing to bet. I made 254 whp with HSR and 1.6 rockers (which i dont think added that much power over stock 1.5's). thats around 310 crank hp. ran low 13's all day in decent weather.. On a good day it went 12.9's

My buddies L98 made around 250whp as well with SLP runners and TPIS base, ported plenum, custom chip. ran mid 13's in the summer on street tires and stock converter...very quick setup. His car would probly have matched my HSR setup if he had same converter/slicks.


A cam install would be roughly 300-400 bucks plus parts for the cam which will be timing chain, valve springs, possible shims/retainers/offset locks to handle lift of the cam depending on what cam you get, and possible rocker arms.

Mild bowl work on the heads will probly run near 200-300 bucks. more serious work will be 400-500 bucks

 

all the mods in my sig minus (ZZ4 cam and Brodix heads and 24lb injectors) had me at 251.6 RWHP which is about 300HP++ at the flywheel. That was with blown head gasket between cylinders 3 and 5. Sure it done much better if the head gasket wasn't blown..lol... Ran bottom 13s all day(Gtech 12.90s) . Then was in the 2/07 issue of GMHTP turning those time in 100+ temps at bolton shootout on 8/1/06. Cars alot faster now after the head/cam change

 

well i think ill do about what orr89rocz said, go ahead and port out my plenum/ runners/base and match as well. then probably do the hedman 68470 ( http://store.summitracing.com/egnsea...429+115+400143 ) and one of those Y pipes on that page, not sure what the difference is. then ill probably put in some 3.73's and a good tune and be done with it. plus ill do all the free mods, and a few small things like k+n filter and such

that should keep me under my budget and give me the extra pep im looking for. what do you guys think?

 

thats a great place to start. you'll see a nice gain in performance with those mods. Then if you want more, you'll know where to get it. After those intake mods, the heads/cam become restriction.

Do some free mods, gut the stock airbox for sure. I also liked the throttle body coolant bypass mod. It does help keep the TB/plenum cooler after driving around which does help cool the incoming air charge

Also have you considered upgrading the torque converter? 2800 stall speed would be a nice compliment to that combo and be REALLY fun on the street when you mash the throttle down. It was a big difference driving a stalled car over the stock stuff

 

personally, i have never driven a car with a stall. what do they run price wise and hows the installation process. could i do it myself or would i have it hired done? any particular one i should look into?

 

if u want bang for ur buck... dont bother with the stock heads... rebuilding them and having sumone port them is gona cost as much as a better aftermarket set.

and HSR is a better intake, but u have mods to make. such as make ur own fuel lines, cant run the stock chip (tuning), its taller than the TPI so it doesnt fit under most hoods, u also have to get the HSR fuel rails.... they are 250$ with the adjustable regulator. which u will need for tuning etc.

if u have SLP runners, i would port them, port match the plenum, port the plenum behind the TB etc, the port the hell outa the stock base. so thats...
0$ 1000$ left
shorty headers/ypipe (headman or edelbrockor summit)90$
http://store.summitracing.com/partde...5&autoview=sku

ypipe 100$
http://store.summitracing.com/partde...5&autoview=sku
cat delete ( 3"pipe) 0$

aftercat 3" pic any tone u like. 300-400$

id say u got about 500$ left.
70$ for an adjustable fuel regultor.
i would put the 400$ towards heads, aftermarket. dont mess with the stockers. u could get a pair of irons for about 600$ or 800$ for aluminum now... u dont need to touch the cam unless u do the heads. u put a great cam with cr@ppy heads and u got cr@p. heads will give u more power. thats up to u... but while the heads are off its a great time to do the cam since most of the hard stuff is outa the way.

these are things i would do if $$ was an issue. might wanna save up for about 1500-1700$ and do it all at once, exhaust,heads,cam, etc. u'll def have over 300hp with all that.

the other thing is the HSR isnt really that cheap lol. i thought it was too but the intake is 310$ the fuel rails are 250$, automatic tune is 150$, the holley adjustable regulator is this stamped peice of CR@P!! so a billet kirban unit is perfect thats 100$. then u have braided stainless fuel lines etc and fittings... thats prob 30-50$
ur already up to... bout 850$

 

HSR complete with fuel rails is around 550 these days. I got mine for 510
fuel lines cost about 80 bucks or so. And you really dont need a tune for it, but you can greatly benefit from one, as you can with TPI intakes as well.


A converter will run anywhere from 250-1000 bucks or so... depends on the brand name, some are higher quality and more efficient. I got a midrange converter...Edge Racing and LOVE IT. good quality and efficiency at a good price. 550 shipped to my door. Installation i didnt do, i had it installed while my trans was being rebuilt. I dont think it cost much to install one. Could do yourself, just need to take the trans out.

Generally you will want a stall speed of 2600-3000 for a bolt on TPI L98 car for best performance and good street driveablity. Keep diameter of the converter down, smaller is more efficient. My Edge is a 9.5" converter. some like TCI/B&M that are cheaper use stock like 12inch size, which isnt as efficient. you also want to retain Lockup feature so it will drive like stock when at cruising speeds.

 

CHEAP: port your heads, plenum, and intake manifold. all u need is a grinder and bits. get an adjustable fuel pressure regulator and set it to bout 50 psi. $60. higher flow air filters from K&N $50, tear out all that crap blocking the airfilters like that stupid airdam thingy, SLP makes a bigger box which allows more flow but search the web for that, probably $100, bigger throttle body for about $200-$400, headers $300, labor for headers and exhaust can vary. that puts u at about $800 bucks and about a weeks worth of work and can give u qiute a bit more hp!

 

what does it take to get the intake manifold off, right now ive got everything off down to the fuel rails. will i have to take out the distributor? any tips on doing this would be great.

 

take the rails out with injectors still intact. you gotta pull up on the bottom of the injectors to pop them out of the base manifold. take off the 4 bolts holding the rails down. move the rail assembly to the side somewhere.

unbolt the distributor hold down and remove it but make sure you know which way the pointer is pointing so you can re-insert it too keep timing close on the next start up.

remove all the intake bolts and its ready to be removed. the gasket/silicon/rtv on the block will hold the manifold down, so pry it off if necessary with a flat screw driver.

 

sounds easy enough

 

well with a grand ur not lookin too good.. headers exhaust and ur feul system are the first thing a good performance tech would say.. no point in inter engine stuff if it cant breath.. so get exhaust and headers done 500 bucks.. do all the free mods duh lol.. get a throttle body space (80 bucks jegs??) as u asked about a stall.. err 2800 is a bit much for a daily driver but then again ive seen guys daily drive charged 383's.. b&m's holeshot 2200 stall is about 180 on jegs and is an amazing street converter ull see huge low end and mid range power but up around 4k rpm it starts to perform liek a stock... seriously aside form a shift kit a higher stall is the best thing someoen can do for an automatic car.. and dropping a tranny in our cars is maybe a 2 hour job install included for a decent mechanic...

 

well im not sure if its in the budget for right now

headers and y pipe installed (by me) = 300
3.73's and professional installation = around 300
custom tune= i have no idea, i need to find someone local to help with this, or something
plus little things like gaskets and k+n filters and things will add up , i dont know, we will see

 

shop around and look for some deals.

a converter is nice, but not necessarily needed. you could hold off on the gears but it would be a nice gain and feel great on the street. Gears are always a good mod. not a bad match too for SLP siamesed TPI setups and stock converter. My buddy ran that combo just fine and went mid 13's on street tires... thats a stout running TPI bolt on car. You'll have fun with it.

And with those bolt ons you wont really need a custom tune, you can get by with tweaking the distributor and fuel pressure with a adjustable regulator. My guess is the car will run fine on stock tune and with some timing advance, you'll pick up 10-15hp on a stock motor.

Do you have a catback of some sort? A complete exhaust system is needed for best performance.

 

Don't use the y-pipe linked above, it only has a 2.5 inch outlet.

1. Do headers/catback first, making sure it's 3 inch from the Y collector back (including the cat converter if you're gonna run one).

2. Get rid of the factory firebird air filter cannister. You could fab something up yourself or buy an aftermarket cai.

3. Port match the base/runners/plenum. Port the plenum behind the throttle body opening.

4. Buy chip burning/scanning equipment.

I don't think I'd waste money on gears for a stockish L98 car, especially if you've got 3.23's now, they really don't need it. I don't think I'd **** with a converter either.

 

+1 on skipping the gears. My 91' has 3.73's and it noses over bad at the 1000' mark because it's out of the power band. It would go faster with the stock 3.23's. Not to mention taching 2800-3000 in OD on the highway sucks.

I'll agree with porting the plenum & base, using your SLP runners, & getting a set of headers. Those mods should fit into your budget perfect and not affect drivability.

If you have any money left over, invest in some suspension mods. What good is all the extra power and no way to put it to the ground?

 

Well said 86, I've always thought that the optimum gears for a L98 were 3.08's........ These things make Geo Metro like power after 4500rpm, so why not keep em at an rpm range that they at least make SOME power?????

 

i loved my 3.27's for my TPI. the 3.42 gears werent too bad either for TPI. For big tube setup or siamesed, 3.42-3.73's are best.

 

this is all wat i stated above, max gears for a TPI are 3.42. 3.23/3.27 are great, and 3.08 will not work any better, they will just give u alil better highway. dont mess wit gears. do your intake and exhaust then take it from there

 

yeah thats what im doing, i am almost done porting the intake, its all gasket matched, all i need to do is go through with a roundish tip and clean up some of the rough/edge spots, then its going back on. i already have felpro intake manifold gaskets and i plan to use RTV black for the "china walls"

 

If ur gonna listen to ANYBODY, Listen to Orr89RocZ. He has THE FASTEST Bolt-on car on here. Listen to him and spend ur money wisely....Just let him spend your money for you. Good Luck.

 

yeah i am listening to him (no offense to anyone else), he knows what he's talking about and he has stuck with this thread and been very helpful,which i appreciate very much. i hate it when people just give you a short, unclear answer and never come back to a thread to explain or help more. so thank you Orr89RocZ

 

My car makes around 300-310 fly.

 

I'm sure i'm not the fastest but i've done pretty well with what i have I think there is a GTA with less mods running faster than me. If i had another year to play with it i'm sure i could easily get this car into the mid 12's with not too much more work But my bolt on days are over

89IrocZ350TPI has another great running bolt on car. Just as much power as my motor made. Pretty much full bolt ons either TPI or HSR will make 300 crank hp.

TPI-Formula350 has a great superram bolt on car too. Same power as my car