Battleshark3000

I bought my first car this spring, and after driving it for a few months i've decided that since I plan to keep this car for many a year, I want to squeeze a little more power out of her. However I have never swapped a motor, pulled one apart, etc. so since you guys seem to know what you're talking about, I figured i'd ask here. any help would be appreciated.

It's a 88 trans am GTA, with Accel super coil, 8.8 spark plug wires, and distributor cap. plugs are on the way.

KyleF

Do you know what rear gear you have?

You biggest bang for the buck mods that stand the least chance to cause any running issues are:

Long Tube headers with a true Y-Pipe
3" Catback
Modify air box and get cold air to it
Lower rear gear (3.42 or 3.73).

I would suggest you first invest in a scanning set up. Then you can check long term fuel mixture, knock counts, and general health of your car. Mods won't help if it is not running healthy. This will also allow you to:
Bump base timing some if it will take it by verifying knock counts
Get and adjustable fuel pressure regulator and make sure your A/F ratio is in the right spot
Seek help on the boards in getting a custom chip to exploit any other modifications you do.

But really before you start modding, give you car a good once over. Check the timing, clean the IAC and do a reset procedure and dial in your TPS and idle screw. Check your plugs, see what they are telling you. Clean your throttle body, check your oil closely for any contaminants. Get a scan and see where your BLMs are. If you are going to keep it for years, don't let the mod bug get you ahead of ensuring proper operation.

GeneralDisorder

iTrader: (1)

Headers (Dyno-Don are my preference), rear end gears (3.4x, or 3.7x), and a 2500-3000 stall converter. Corvette servo, shift kit, etc. Tuning may be required to get the most benefits from all this, but that can be done via email for these small changes.

These make a huge difference in the feel of the car. Peak power is probably very close to stock - maybe 10-15 HP increase with headers. But you will shift the peak power around to where you can use it easily off the line. Top end will remain virtually the same. Changing that requires more than "bolt on's".

GD

KyleF

You may also consider going to a set of roller tip rockers, on a previous thirdgen I went with a 1.6I/1.5E set.

I would say the biggest Seat of the Pants feel will come from rear gears, depending on what is in the car now. If you were going from a 2.77 to a 3.70 (assuming GTA is a 9bolt 4 wheel disc car) that is roughly a 30% increase in torque multiplication. Even if you have a set of 3.27's, it would still be about a 15% increase. You will feel the difference. Also, check if you have an aluminum driveshaft. This is also another bolt in that will reduce overall weight of the car, reduce parasitic loss, and reduce the moment of inertia resulting in better acceleration and braking by being able to speed up and slow down the driveshaft easier.

There are mixed thoughts on under drive pulleys, but these are also a cheap easy bolt in that has proven to free up a small amount of power. Just have to make sure you don't have any charging or cooling issues.

dmccain

iTrader: (2)

I can tell you that adding my mild S10 torque converter (maybe 2200 stall) , shift kit, and 3.73 gears made my car feel like a total different car all together. Its still slow but much more responsive. Good thing is these changes aren't a waste of time they will transfer right over to my 350 swap. I didn't spend a dime on the 305.

sack23

iTrader: (2)

I agree with Kyle, on the scanning tool to assure everything is running properly. Since you already took care of the ignition part of things a fuel pressure regulator will help. They don't cost a lot and installation if simple. For me roller rockers (1.6) made a noticeable difference specially higher in the Rpm range. As for gear and headers it made the biggest difference to my car and I only went from 3.08 to 2.27.
Sac

Drew

iTrader: (58)

3.73 and potentially 3.42 gears with a 700R4 are going to push a 350 TPI into higher RPM faster. TPI has a torque curve that favors low RPM. So in other words, it's a trade off. In some cases you're going to lose performance because the gearing is going to force the engine to run out of breath faster. Now if you have 2.73 or 2.77 gears, yeah, upgrade to 3.23 or 3.27s, or push the limits with 3.42s. 3.73 gears will potentially run slower 1/4 times.

Battleshark3000

I'll have to look into these, I haven't checked my gears yet, so i'll have to do that over the weekend. i really appreciate the input.

burnout88

KyleF

That is the worst bit of advice I have ever heard. At any given RPM you are getting more mechanical advantage to accelerate the car. You will only potentially go slower if you are running out of RPM at the top of then1/4mile, and even then to a point your ET may still be better. I have 3.70s and it has a lot more pull at all RPM and I only dream of trapping at a MPH high enough to run out of RPM.

Abubaca

iTrader: (3)

Assuming all the basic tune ups have been done, I'd look into Dyno Don's headers and the catback of your choosing (I like the Hooker system), and a rear gear and torque converter. I'd leave the engine completely alone. I'm not as familiar with the Pontiac/GTA airbox, so possibly a better cold air intake, but I wouldn't touch the engine beyond tune up parts. My experience has been that exhaust, gears and converter will make a BIG impact right away, and will serve you well for a long time. Once you get into the engine it's a pandora's box of never ending bolts ons chasing minimal gains at each time until you're left with a hodge podge of mismatched parts and finally decide to just build an engine from the ground up. If you are able to predict what you goals years from now are, and are willing to do one mod at a time to get there, then great....many of us are not, and the goal posts are always moving.

...that being said, and type of diagnostic equipment, scanner, wideband, fuel pressure gauges etc. etc. are great tools to get familiar with, and will help you learn and diagnose, on any combo you ever build, on any car.

Street Lethal

iTrader: (16)

I think you completely misunderstood what Drew was saying, as well as misunderstand the difference between ET and Trap. You may have cut eight tenths from your ET by swapping to 3.73's which makes sense because you decreased your 60' while you were at it, but how much mph did you gain from the gear swap? None. You couldn't have if you crossed the line at the same RPM. That is what he meant when he said potentially slower, because a smaller gear (higher numerically) reflects a lower mph at a given RPM compared to a taller gear (lower numerically) at the same RPM, not to mention the same horsepower and RPM band in both instances, which are both low...

- Rob

Drew

iTrader: (58)

With what other supporting modifications? What ratio did you swap from?

"a lot more pull" sounds very scientific. Haven't we already established that you don't understand how gearing works?

Look, I don't have the time and patience to climb into the slop and argue with idiots, so I'll just drop a link and leave it to an accomplished author to explain why you don't want to just stab in a set of 3.73 gears without giving all the possible outcomes consideration. https://thirdgenfbody.wordpress.com/...eptember-1996/

God help the OP if he's just getting his feet wet and people are suggesting he swap from a 2.77 to a 3.70 ratio as a first mod. Some of you should be ashamed of yourselves for not explaining the negative potential of your suggestions.

KyleF

You can think you established what ever you want. The only negative is running out of RPM at high mph. I don't think anyone on this thread is going after land speed records. What matters is ET, not mph in a race, unless you are running an event that the goal is top speed.

What negatives? A 3.70 You will lose a few MPG, you will turn 2500-2600 RPMs at 75mph (up from 1900 with a 2.77), you may run out of RPM at the top of the 1/4 mile if you have enough power. Modifying the 700R4 to shift into OD at the top of the 1/4 won't help much unless you have plenty of power to pull with.

Theoretically a car with 245/50/16s and a modified 700R4 allowing you to shift into OD :
2.77 Top Speed at 4600 RPMS: 180mph
3.70 Top Speed at 4600 RPMS: 135mph

2.77 at 75mph: 1906
3.70 at 75mph: 2546

Force form wind resistance increases exponentially as speed increases. A 2.77 gear with an L98 is not getting to 180mph. Just does not have the HP (Making torque at Higher RPMs) to get there. When you are looking at a pretty much stock L98, it is going to run mid 14s and possibly a low 14's if all conditions at the track are perfect. This is at a trap speed of low 90mph. So, st 95mph, with the 3.70 you are just shy of 4600RPMs, genrally this tends to be the top of the TPI "Swee spot". A 2.77 would be just over 3400 RPM leaving some power you never got to use on the table. Now with the different gearing you will see different performance and won't trap the same speed, but you can see the car with the 3.70 is using more of the engines power before reaching the top of the 1/4 mile and can exceed over 4600 RPM even though power will start to drop off quickly. With a pretty much stock motor you would be better holding out 3rd gear than going into OD.

With gearing, like other mods on the car, it is best to have an overall plan of what you will do with the car. I could see a 3.70 requiring another shift in the 1/4 mile. Depending on what ET/MPH you are able to get based of engine mods it could possibly be a tick slower than a 3.42 if you you are running out of breath too early on a given track. Again conditions at the track have a lot of effect on what times you are turning in on a given day. Also, consider if you are going to change your wheel/tire combo, a change in diameter will effect the overall gear ratio.

All of this is in discussion of a car you are taking to the track and launching from 0 and running a 1/4 mile. I really don't do this frequently with my cars. I tend to be more influenced on how my cars perform between 35-95 mph, passing situations, and performance form a roll as this is how my cars get driven 95% of the time - weekend fun cruises, shows, and cars & coffee events. I can't even remember the last time I got to line up and race from a dig or a roll on the street. I guess having a family, mortgage, insurance rates on multiple cars, and needing a license to drive to work everyday keeps you from looking for races on the street. For this purpose, the 3.70 is exceptionally great. If I was planning on going to the 1/4 mile on a weekly basis I would probably lean more to the 3.42's for traction for hard launches, making sure you had some RPM left as you did other mods, etc. A L98 can rev to 5500 RPMs:

At the top of 3rd:
2.77: 152mph 5518RPMs
3.42: 123mph 5513RPMs
3.70: 114mph 5528RPMs

To put this in perspective of the engine power it takes to trap these mph (and traction/aero dynamics, etc),
A trap speed of 150mph is the realm of 9 second cars (McLaren P1 9.8@148.0mph /Koenigsegg Agera R 9.01@151.9)
A Trap Speed of 123 is in the realm of a low 11 sec car (Mercedes CLK GTR 11.12@123.1 / Callaway C16 Corvette 11.11@123.1)
A Trap Speed of 114 is in the realm of low 12 second car (2010 Mustang GT500 11.95 @114.5 / Lotus Exige S 12.03 @113.08)

A stockish L98 will never put down enough power to trap in the 120s. However, I would never suggest going lower than a 3.73 on a 700R4 due the the low 1st gear.

Drew

iTrader: (58)

Dude. What part of "I don't have the time and patience" is hard to understand? I dropped the mic three days ago. I'm not going to read a wall of text, when you clearly don't know what you're talking about.

My point has been made, if you still think it's the worst advice you've ever read, maybe you should be writing for GMHTP.

Street Lethal

iTrader: (16)

I really try to avoid these discussions, but Kyle, you are contradicting yourself over and over again, you really need to stop because it does not look good on your end, not to mention Drew is trying to help you but you're getting too defensive. Putting aside the fact that the OP does not intend on staying "stock", you actually had it in you to say these words;

That is absolutely ridiculous, because all ET tells you is how good you can cut a light. Trap Speed (mph) tells you your horsepower. Not to mention, your figures are dead wrong. 135-mph is nine second land, not 150-mph. Here is where the contradiction on your part lies, you're stating that mph doesn't matter, only ET, yet you use a McLaren P1 to justify yourself buy saying that a McLaren P1 ran a 9.8 @ 148, when it is the mph that is telling real racers that it is capable of a lot quicker than just a 9.8 second pass, and that it was babied off of the line, whereas you're using it to justify your argument when it wasn't even a real pass on the McLaren's part. Telling yourself that 150-mph is "nine second land" because you're basing it on supercar road and track is hilarious, which is why maybe writing for GMHTP was mentioned...

Factual proof goes a long way, so make a full pass with 2.77's, lets see the slip, install 3.73's, don't touch the engine, and make another pass. Let's see the new slip. You'll find your sixty foot dropped a tad, and your ET dropped a tad, as for every tenth in your sixty foot, about two to three tenths are effected in your 1/4 mile ET. MPH stays the same because horsepower did not change, in fact it might even drop because your blowing through your RPM band essentially killing your rate of acceleration...

Horsepower (mph) wins races.

- Rob

GeneralDisorder

iTrader: (1)

3.4x or (maybe 3.7x) will be more "fun" on the street than 2.77 with a relatively stock L98.

I don't doubt that it would be worse on the strip. So it depends a lot on what the OP is doing with it. I couldn't hardly stand to drive my LB9 with the 2.77's on the street. I went to the 3.70 because it's the only aftermarket gear set you can get for the 9 bolt. No regrets on the street. Lots more smiles per gallon.

I will re-evaluate my gearing needs when I swap to a pro-charged 400. Probably won't be using the 9 bolt at all though.

Depends on what he's doing with it, and really even an L98 with bolt-ons and sticky tires could destroy that 10 bolt if it hooks up right.

GD

KyleF

Actually I pulled it of a list of many many cars, just selected it as a known. All the cars grouped close by both ET and MPH.

The NHRA or any class doesn't race for MPH, they race for ET. Combined ET and Reaction time to be precise.

Power, ET, and MPH are related. The point I was making and wrote out is a near stock L98 doesn't have the power to get to that MPH to worry about it unless you are going to a big build. Not sure what contradiction you see in that. Oh well.

For a mild L98 the 3.70/3.73 gear is fine and excellent for the street.

Battleshark3000

As to what I'm doing with my car, it's my daily till winter. So i'm not concerned with my times. yet.

Drew

iTrader: (58)

But you're completely missing the fact that the L98 has a torque curve that favors lower RPM, and that pairing a 3.73 rear gear with a 700R4 is going to force the engine to turn more RPM at lower speeds. You don't seem to understand that you're trying to run the engine outside of it's power band. All you're going to do is hit the Tuned Port wall at 4500rpm that much faster.

Not really. As already mentioned, the L98 already makes plenty of torque at low RPM. It's already enough to spin the tires easily. On the street with street tires, it's just going to be that much more difficult to hook up and put the power to the ground. When you consider that it's also going to be less fuel efficient, it's less than ideal for the street.

Seriously though, break away from all the distractions, and go back and read the four page article I linked earlier in this thread. Read it until it makes sense. Pay extra attention to the part where he explains that 3.73 gears behind a 700R4 is equivalent to 4.56 gears behind a Turbo 350. Also the part where he talks about how putting 4.10 gears in a virtually stock L98 88 T/A "was an undriveable mess".

88IROCvertZ

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Street Lethal

iTrader: (16)

GD, think of it this way, if high RPM were more important than an engine's RPM power band, then why not just install a 4000 plus stall speed converter into a TPI vehicle equipped with 2.77 gears out back? There is a reason why guys target under 2500 stall speed converters when running Tuned Port Injection, and that is so they don't blow through its' power band. What good is having peak torque and horsepower below 4500-RPM, while running gearing that allows you to blow right past it. Horsepower is needed to turn a prop at a given load and RPM, and if the horsepower is not there at higher RPM's, the engine will bog back down to where the power already is because it simply cannot overcome the load, so your rate of acceleration suffers.

Again, you have to understand how it works. It takes X amount of horsepower to turn a prop at a given load and RPM, so once that value is met and exceeded, the taller gear (lower numerically) wins, end of story. Let that resonate a little bit. Two vehicles making 800 plus horsepower, one running 3.73's and the other 2.73's, and I can assure you that the 2.73's will annihilate the 3.73 equipped car. Again, I will say it for you another way so you understand. At stock horsepower levels, a 3.73 swapped into a vehicle from 2.77's might get a vehicle closer to a 1.50 sixty foot for a quicker ET, but its' mph will not change and it will not be faster. Now, add more horsepower to the 2.77 equipped vehicle to meet that same 1.50 sixty foot, because all it takes is increased horsepower for ANY ratio to meet a targeted sixty foot, and watch that 2.77 annihilate it...

- Rob

Edit: By the way, here is a good example. This Integra Type R raced a Callaway Twin Turbo Corvette w/TPI, the Integra was spinning close to, if not over 8000-RPM, and the Callaway was spinning under 6000-RPM. Callaway's came with very tall gearing (lower numerically) specifically for the TPI's powerband, as per Callaway himself. This is not the famous Sledgehammer C4 Corvette, it is a basic and entry level TT Callaway C4's that made UNDER 400 horsepower up top, but OVER 500 pound feet of torque down low (hint hint) while the Integra Type R made way more horsepower up top, and essentially nothing down low. Who gapped who... and how badly?

GeneralDisorder

iTrader: (1)

I get all that, but with 200 HP, and good sticky tires you aren't going to even turn them over with a 2.77. I tried.... maybe the L98 would have but my LB9 wouldn't.

I'm not talking about even going to the track, or measuring anything like 60 ft or ET, etc. I'm talking about bringing the back end around, doing some burn-outs, etc. With a stock power, 700R4 and 2.77 gearing..... I can tell you it's not a fun configuration on the street. "Fun" doesn't always mean fast. In fact if you obey the speed limit it's not really possible to see the advantages with stock power. With more power I don't doubt the higher gears would be fine.

i understand your reasoning, and I'm not an experienced drag racer, but I do have a question - why did GM put the 3.2x and 3.4x gears in like the B4C cars, etc?

GD

Drew

iTrader: (58)

The reason GM used 2.77 gears was largely based on corporate average fuel economy. 3.23/3.27 or 3.42/3.45 is a reasonable upgrade to gain a bit of performance because it's not a radical change in gearing. It doesn't force the engine outside of it's power band.

Abubaca

iTrader: (3)

I went from a 2.77 to a 3.27 on an headers/exhaust only L98, and the difference was pretty impressive. I'm now running a 383 TPI, and a TKO, and the powerband, while much more powerful, is shaped pretty similar. I've done the calculators countless times and a 3.42 would be ideal. I'm actually still running that old 3.27. For now.

Orr89RocZ

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1986Z28OWNER

iTrader: (1)

Do you have the slightest clue what you're talking about??? Reaction time plays ZERO effect on ET. NONE whatsoever.

Street Lethal

iTrader: (16)

But that is only a fraction of the information needed. What RPM did you cross the 1/8th and 1/4 mile line in all three instances, and if your targeted RPM was lower when you ran the 2.77, then why didn't you increase boost pressure/horsepower to get RPM back up there with the taller gear? You're going to mph faster with a taller gear at the same RPM, but running a lower RPM during a comparison while not compensating with horsepower to even it out completely defeats the purpose.

- Rob

RS Chris

No kidding. When did this place turn into Yellowbullet? Guy just asked for some advice and now all the children are in here name calling. Spend more time in your post trying to disprove each other instead of focusing on the main goal of this place, to help each other. And you don't do that by acting like dicks.

Orr89RocZ

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Street Lethal

iTrader: (16)

Justin, that is where we differ. Racers choose power and RPM based on their engine's characteristics. If you're going to rely on what GM did with these cars thirty years ago, whether rear ratio, or tranny ratio, then build around that, for a stoplight to stoplight daily driver, then that is a different story. It won't be to its' full potential, you will just make it as quick as it can be based on what it already has. Just like a bin, don't touch an L98's SA even though it drops after 4500-RPM, just work around it rather than go in and change it to fit the engine's characteristics. We study data logs for drag racing for a reason, not just to tune air/fuel and spark, but to see where peak and average are embellished, and compensating based on that. Again, if you disagree you disagree, there is no way for me to say it any other way...

- Rob

Orr89RocZ

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Abubaca

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This thread is SO FAR BEYOND the original intent of the question.

To Battleshark, the OP....There is a lot of good advice about where to start and what to do in this thread, all of which have nothing to do with rear gear ratio. Look into all these ideas and do some research...come back and ask a few more questions. Most of you ideas will work, some won't, and before you know it you'll have your own experiences to comment on when the next guy asks these questions!

As for rear gear ratio, I think a 2.77/2.73 is really the only bad ratio out there...though many of us have still used them and had lots of fun! ....anything deeper, from 3.08 to 3.73, will work, and will deliver different balances of economy, acceleration, highway cruising comfort, performance, quarter mile times etc. etc. There are countless factors which ultimately contribute to the "best" ratio, and it kinda sounds like you're not ready to make that choice just yet. I went from a 2.77 to a 3.27 for about $250 bucks, and I swapped the entire rear in a few hours. That's how I made my choice. Building a 600 horsepower nitrous motor? You'll probably wanna do a little more in depth research. I think you get where I'm going.

Orr89RocZ

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zya5point0

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Justin, I agree, my head hurts too, lol! Poor guy just asked what he thought would be a simple question. Problem is there is no simple answer. And obviously we've all had different experiences with different approaches. I love 3.73's in a daily driven tpi car, but... Only if most of my driving is local with just an occasional road trip. And I also wouldn't go that low unless i absolutely knew i was gonna upgrade the the tpi for more top end. All I know is my experience. As I've mentioned often, I already had super ram runners on my stock base back in the day on my 86 lb9, and going from an on open 2.77 to 3.73 posi cut a solid 6 tenths off my quarter mile. Car was crazy fun around town! But i do agree starting out by going thru the engine with a fresh tuneup and making sure everything is 100% is a must!

daferris

iTrader: (8)

I'll cut to the chase here .. I have a '88 IROC 5.7 with a 700r4 ( soon to have a T56) I have never drag raced it but I do drive it on the street and run track day events on a 2.1 mile 11 turn road course ( Gingerman Raceway ) when the car was stock I tried 3:73's lots of fun on the street easy to lite up the tires ect... But on the track after about 15-17 minutes it would overheat because motor running near red line a fair amount of the time each lap. I removed the fog lights that helped some. Changed to 3:42's for the next track day no overheating. Still could light up the tires just not in 3rd gear anymore. Still had tons of fun cruising around on the street. overall I was just happier with the 3:42's
for what it's worth that's my 2 cents. In the end it's your car and your money. The best advice I can give is make a relistic plan. What do you want to do with your car? Cruise town? Drag race? Track it? Or a compromise of some or all of that? How much money do you want to spend? Above all the more radical the mods to the car and the drive train the potential that you will have to wrench on the car more to keep it running at it's peak. That also costs money and time. So spend your time first thinking and planning that will then 1) save you money in the long run 2) make this hobby more enjoyable for you because the pieces of the puzzle will fit together for you...

ray jr

iTrader: (2)

lol , i was thinking the same thing ..

AaronIROCZ

iTrader: (5)

Ok guys, I have cleaned this up some, you need to keep this on topic, cut the arguing and keep it civil. Anymore swearing or name calling I am handing out infractions. Keep it clean, and carry on.

sack23

iTrader: (2)

BattleShark
I will try to make it to the Track tomorrow here in south Florida if weather permits. I will post my time slip as reference. I only have bolts on's so it might give you some current data and Ideas.

sack23

iTrader: (2)

Below some times from yesterday at the track, you can use as reference. Weather was around 85 degrees and humid. Which by the way I am no expert, been there around 3 or 4 times only.

1st 15.015 @ 96.21
2nd 14.725 @ 96.46
3rd 14.625 @ 96.40
4th 14.580 @ 97.14
5th 14.418 @ 97.45

First 3 runs, I was shifting at 5500 rpm. I was dead in top of third crossing the line (5700rpm)
Last two runs shifted at 5000 rpm and was able to bravely shift into fourth. I was also very surprise to run relatively the same speed with such a variation in ET's time.

Bolt on's that I felt a difference when installed.
Edelbrock Headers
Gears 3.27
RR's 1.6
Under drive pulley's

Other Bolt On's
FPR @ 48PSI
Air Foil
MsD ignition.

Hope this gives you some ideas.

Best
Sac

cmk-2

iTrader: (1)

I now this is an old thread I started but it still holds is a good source of information on the 5.7 TPI. Truth vs marketing hype.

https://www.thirdgen.org/forums/afte...s-any-one.html

Orr89RocZ

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sack23

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Thanks Orr. Now I need to work on my 60 ft times.