I own a 91 GTA with a 305 TPI auto. The car has 109,000 km (67,000 miles) on it and has couple of mods done to it so far, SLP catback exhaust and air foil. The first time ever racing at the track I ran 15.96 at 86 mph. The next time I ran a 15.73 at 87 mph. With a borrowed homemade CAI I ran 15.62 at 88mph. I am hoping to run a 15.1-15.2 with the mods I am planning on doing. My arch nemisis owns a 91 Z28 with a 305 TPI auto. He always managed to stay a couple tenths ahead of me all last summer and always reminded me who had the faster car. This year I want to smoke his a$$. What do you guys think of my planned mods? If anyone has some suggestions for other cheap mods let me know.

Holley APRF
Third Gen Resources 3.5" Cold Air Kit
March Power and Amp Pulleys
Bumping up the timing from 6* to 10*
TB Coolant Bypass
Porting the plenum
Bosch +4 Platimun plugs
Cleaning the plenum, runners, and throttle body
Global West Suspension Steering Box Brace
Cleaning the IAC
Making sure that the Thottle Position Sensor is at .54

I always run premium gas and Mobil 1 Synthetic, and almost all of the fluids are synthetic and have been changed recently. I changed my fuel filter, tranny filter, PCV valve not that long ago too. The wires and distributor cap are GM with about 10,000 miles on them. Should I make any ignition upgrades? Also is it worthwhile to get a different thermostat than the factory one?

 

gears will probaly help u alot and if u really want to but a hurt on him go for the nitrous kit.

 

i thought those 91 305 tpi ran 15.2 with the cheap tbi exhaust and 2.73 gears, i'm pretty sure ed mayer has that car with a vert , and that what they run from factory , i have no clue why you are running slow q-miles

 

Keep in mind that these times are uncorrected. Corrected, his times would be about 15.35 at 91.

Don't know if ignition upgrades would make a lot of difference, but every little thing you do might give you an extra .05, but likely not worth the $$..

I'd say try the free mods and cleaning, etc for May 9th and then go from there.

 

I know my times are slow. The track that I race at isn't prepped and I'm about 1600 ft above sea level. I wish my car could run high 14s- low 15s completely stock like other people with 305 TPIs on the board. I'm hoping to get that with some minor mods...I have 2.73 gears which don't help either. I'll maybe look at getting 3.73 gears later in the summer.

 

andy 91 gta
look for ed mayer he is the moderater here, he will tell you what you should do to your car, he is running 14.1 , all he did was gears 3.23 , stall, headers, chip tuning, 14.1 is an awsome 305 time i wish i can get there,

 

oh by the way my 86 305 tpi peanut cam , would run 15.7 all there is gears.3.42 , so with a decent cam that should shave a good second ,

 

um.... i ran a 15.3@90 mph with a chitty 60' ft time... Your 305 should be running a LOT better then high 15's... i have basic mods that are in the sig... Your mph is showin you should be faster in the 1/4. With a good hook you should be around 15.4-15.3. I do not recommend underdrive pullies if you have a system or any major loads in you car. The underdrive could destroy your alt. I dont have a system, and it killed it and started a very bad chair reaction. The Plat 4's are dumb and wont yeild you jack. Save that money for a new set of gears. Putting nitrous in your car is kind of a big step. Deff. port your plenum and gasket match your runners and plenum. Also, if you can get a hold of a die grinder and a compressed air tank, you can tear away at the base. That is a big choke in the TPI system. Good luck man and i hope you beat that car, even though im a die hard Camaro fan.

 

Bigals87z28

I am planning on getting the Power & Amp Pulleys, March says they don't put as much strain on the alternator. Has anyone had a problem with these pulleys?

I already bought some Plat 4s when they were on sale. If I change the plugs, I won't have to do it again for 100K so I might as well do it.

 

you guys forget GTAs are little on the heavy side

 

What makes them heavier ? i always thought they were the same (body wise) except the fenders and wheels (which the gta wheels are accualy lighter)

 

I don't know every reason why but I think the headlight motors and that rear spoiler is heavier then one off a Z.

Every road test I have, GTAs are about 50-100lbs heavier. Also, they were gnereeally speaking, loaded up with most or all options.

 

are you saying GTA's are heavier then T/A's or Camaros ? cause the headlamp motors should be the same, and the spoiler is lighter then the poly urathane one on the 1986 t/a

 

I have (had) thoes exact pullies you wana buy, and im telling you, no they are a bad idea. It did destroy my alt which let to a really bad domino effect at englishtown race way... very very bad. I had to replace the alt. I never put the alt pulley back on, but left the crank pulley on, and i still have some charging problems at night at idle. As for the plat 4's. If you dont change your till 100k miles, then that is just dumb. The plat 4's are a waste. The regular plats are just fine, but even thoes are a little overboard on a stock motor. Should of just dropped in some good 'ol AC delco plugs. Almost all thirdgens are about the same weight. Some might be a tad heavier but not that much. Birds did come with a lower rating in HP because of the restrictive air intake compared to the "Y" shapped air intake on camaro's.

 

I am saying GTA's are heavier then Camaros. My 50+ road tests of thirgens say this.

 

Ok, was was just making sure you wernt saying GTA's were all that heavier then T/A's if at all

 

from the tech data.....

Weight of Unoptioned 1987 F-Body Combinations
Model Base Weight
IROC-Z 305 5.0 5-Speed 3250
Formula 305 5.0 5-Speed 3383
IROC-Z 350 5.7 Automatic Overdrive 3341
GTA 350 5.7 Automatic Overdrive 3476

 

DAM fat som'bitches..

 

my friend just weighed his 91 GTA on a road scale.. 350 fully loaded.. was 3385 lbs

gotta check my 92 this year

 

Okay but that's with him outof the car right?
How much gas?

 

Just so you know. The reason that the alternator pulley is smaller is to SPEED UP the alternator so it is putting out better at lower RPM's. By taking off the alternator pulley and not taking of the crank pulley, you are making the charging problem worse, but out of experience with them my car is an alternator eater and it may be because of my underdrive pulleys.(That or my 500watt stereo

Chris

 

Best mod for the buck is headers!Of all the mods to my IROC (see sig) this was the one that you could actually feel.Headers are the first mod I suggest to anyone looking to pick-up a couple of tenths.
BD3

 

on your 86 305 it would have been the cam change, the best bang for the buck, headers 2-3 tenths, a good cam 8-9 tenths
i'm not sure if you are running the 86 305

 

1)AFPR...yes, Makes a difference. Holley AFPR is excellent IMO
2)Cold Air Kit...not familar with the brand, but colder air is better. Ice down the intake in between runs if you can get traction.
3) Pullies...read the new GMHTP magazine for a dyno comparison and charging observation. I am running the crank pullie. I hate driving at night and having to stop at a light...but to me its worth it.
4) Timing advance did not help me any. It may you. Each car is different. Prom tuning is a better alternative.
5)Porting the plenum is a free mod somewhat. Small gain IMO. Every little bit combined eventually adds up to a big bit, though.
6) +4 plugs: do some searches. I would have given you a set of mine if you had asked. I'd try and get my money back. AC Delco
7) Cleaning the throttle body may help some throttle response
8) Brace: ?? Doubt seriously at your power level that it will help. Get some Spohn LCA relocation brackets instead. Low cost...better bite.
9) IAC cleaning...if you want to.
10) Mine is set at .64, works well for me.

The fuel pressure, colder air, and timing changes should produce a nice combination of results. I believe a thermostat will help you. The colder my engine is, the better she runs. There is a certain low temp I reach that I no longer can get traction. I always try and keep it right on the edge. Usually about 150-160 degrees.

Headers + 3.23 posi gears will be big difference makers.

Other low cost measures you may consider:
wires, I have Taylor 8mm. I really like them.
MSD Coil. Probably won't make much of an improvement, but for me it helped the top end.
exhaust cutout
trans go shift kit
If you can get a better breathing induction system (new runners, ported intake, etc.) that will make a nice improvement.

Quite a few 305 cars on this board like yours running excellent times. Check them out.