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Old 12-22-2001   #1
89GTA
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Skull & Crossbones converting my 5.7L TPI to carb

hi, for the past year my trans am GTA hasnt been running good at all. the engine is healthy but there is something wrong with the tpi. ive replaced almost everything on my engine/intake and nothing helps. im gona give up on it and convert it to a carb set up. my question is, what exactly do i need to do this conversion? obviously a new intake and carb, but what about the transmission, speedometer, distributor, cruise controll, etc....? will removeing the ecm affect anything i should know about? i can live without air conditioning, cruise controll and egr related stuff, but right now i just want the damn thing to run. i dont want to run a series of checks on the tpi, ive been there and done that. i just want a clean start with a new carb set up. so what do you guys recomend for my 89 5.7L GTA? if anyone here has done this conversion before, i would really appreciate your input.
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Old 12-23-2001   #2
nblanchard
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I don't think a carb will please you like you think it will. Did you replace the computer in your car with a BRAND NEW one? I would never change to carb, yukky.... In fact, if I get this 1972 Camaro I am looking at... I will probably change that over to a TPI or MIniRam.
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Old 12-24-2001   #3
karfreek
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Thumbs down

You will lose lots of Torque & low end snap by going to a carb setup. I would search more on what is making your TPI so sick...

Jay
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Last edited by karfreek; 12-24-2001 at 11:30 AM.
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Old 12-24-2001   #4
87 GTA 1
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I also strongly agree.The carburater will make you lose throttle response,low end torque and overall fuel economy.And that would be a ***** not having A/C.Knowing these cars if you go unpugging stuff for that setup,it's more than likely to run shitier than it does now.It all reads and works together.
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Old 12-24-2001   #5
ottawagta
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Have you checked your injectors?

I've mentioned this in an old post....I tend to flog the issue, but it drove me nuts.

My GTA ran like crap for 2 summers, so bad I couldn't drive it.
I finally found the problem, my injectors were dying. It's a common problem with the GM Multec style injectors. If the resistance of an injector is less than 13 ohms when hot, it's no good. I had injectors at 3 and 5 ohms!! When the resistance is out of spec, the injector pulls too much amperage and throws the entire bank of injectors out of whack( surging idle, low integrator values due to running rich, backfiring, performance less than a 3.1 L V6!).

GM wants a small fortune for injectors up here, so the answer I found was to buy Ford (actually made by Bosch) Racing Injectors (24 #/hr for my 350 TPI). The injectors are all flow balanced and only cost about $220 US for the set.

The extra 2#/hr flow rate will give an extra kick in the pants (like cranking up the fuel pressure on the stock injectors.

Only problem is that she's parked for the winter, and it'll kill me to put them in now and wait till spring...so I am waiting (impatiently) for spring to toss them in and let'er rip.

Hope this helps.

Merry Christmas and happy New Year everyone!
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Old 12-24-2001   #6
f-crazy
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one word

WHY??
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Old 12-24-2001   #7
karfreek
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You might want to look on ebay. If you think it is physically in the Plennum/Runners/manifold there are tons of them on there going complete for $300-500 in good shape.

I wish you would give us a more detailed explanation on what symptoms your car is experienceing, & what work has been performed on it. Sometimes the most troubleing problems are the easiest to fix. I would hate to see you tear off the awesome TPI setup because of a $50 fix that was not diagnosed. Please let us help you before you go this drastic route.

Jay
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Old 12-25-2001   #8
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Unhappy TPI=$$$$$$

guys, ive changed and checked everything exept the computer. BUT if i do buy a new computer, it would cost me about as much as as a new carb set up. TPI plain and simple just costs WAY too much money to maintain. im not rich, i work for $10/hr canadian and i need something more reliable than TPI. for about a year now ive been on this board and the thirdgen.org one asking questions trying to fix it, but nothing has helped. sure ill lose some torque, but ill gain 100% more reliability. i want something i can work on in my garage with my tools. ive poured over 4000 dollars into this engine so far and ive come up with very little results. TPI has got to be the worst intake in terms of reliabilty that i have ever seen. its not very friendly to the home mechanic
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Old 12-25-2001   #9
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Dood.... i told you a thousand times to change the computer, from the first time I saw you post this problem.. but you decided not too. The computer I got FROM THE DEALER costs 250bux BRAND NEW!!!! and that is canadian!!! I don't see why this is a huge expense when you spent 4000 useless dollars on other garbage. Carburetor is NOT 100% more reliable... good luck on those cold mornings and passing any upcoming emissions laws.
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Best Track Time is 14.396 @ 95.71MPH

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325.8ft-lbs @ 3250rpm (at the wheels)
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Old 12-26-2001   #10
87 GTA 1
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Nblanchard I agree with you mane.I know dude's with half that in the engine that are running prreettyy well.In a carb car the cam is the brain of the engine.With TPI it still is to an extent but the computer is the master mind of the car.I wish home boy would listen to you.But if he wants to lose all the goody's so be it,what can we do.I can really stress the smog factor here in Cali.If you dont got the hook up at the smog shop then your screwed.Thats when rich boy is going to win with his basicly stock t/a with a PROCHARGER runnin down the highway.I think the carb idea is just a bad Idea altogether.Vvvrrrrr vvvvvrrrr oh damn the choke is f ed up on my carb and and the float is stuck can I get a ride to work bro.HAHAHAHAHA
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Old 12-26-2001   #11
ottawagta
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A cheap solution to the computer is that the computers for 3.1L V6's (89-93) in Berettas, Cav's and Sunbirds are the same, and you usually can get'em cheap in the u-pull at a wrecker....all you need to do is switch the prom chip.

I believe there is a listing of swappable ECM's on www.thirdgen.org

Also, for swappable parts, check out the product catalogue at www.smpcorp.com, and you'll see that the aftermarket ECM's are the same for the Chev V6 and V8 for some years. It's also a good reference for other swappable parts for other cars.
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Old 12-30-2001   #12
f-crazy
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god i love cold starts lmao

hey what about digital fuel injection how much is a setup like that?
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Old 01-02-2002   #13
89GTA
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Thumbs down tpi

although i am liveing in an area that has smog laws, that my change soon. im not that concerned with my car being "environmentaly friendly". as it stands right now i dont have the cash for either a computer or a carb (due to christmas, new years, etc.....) but the thing is, what if its not the computer? then i just blew 250 dollars for nothing, AHHH the joys of TPI........ just like the time i blew 200 on a new MAF sensor for nothing. sure, in its time im sure tpi was a wicked system. but its 11 years old now and its failing. most of you guys bought your GTA's either new, or used with a couple grand left over to burn. i blew ALL of my money on this car (yeah im stupid ok, dont bother rubbing it in cuz everyone else has already beat you to it) now im stuck with a lemon, and im broke. a quick guarenteed fix is to switch to carb. at this rate i could continue blowing every cent i save for the rest of my life on useless crap for my tpi wich probly wont even be the right "cure". why do you guys like tpi so much? yeah sure, big torque, good milage and less smog. but from what i hear it starts wussing out at 4500rpm, where as carbs keep goin faster and faster.
also.... i have an off topic question, gta's are unibodys right? so basicaly they dont have the support of a frame, does that mean they will start to twist and warp over time? especialy if you add more hp to their engines? ive heard about subframe connectors, are they a "must have" for people seeking more hp?

P.S.
do you guys have some kind of an unholy hatred for carbs or somethin?

Last edited by 89GTA; 01-02-2002 at 10:06 PM.
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Old 01-03-2002   #14
nblanchard
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First of all.. you answered your own question about "why do we like TPI so much" Its the mileage, while getting torque at the same time... and with a few mods, can easily puch 300 horse, and still get good mileage. I am not saying you're dumb... but there is obviously something wrong.. and I can guarantee its sooo easy, you'll hit yourself. Taking your car right to the dealership for a drivetest diagnostics is the best thing you can do.. yes itis a chunk of cash.. but at least you pin point the problem ASAP, instead of spending 2 grand replacing crap.

Maybe its an internal problem, and the carb may not solve the problem.

As for them not performing past 4500RPM... mine did thatbefore I got the computer changed... now it redlines way too easy, and has good power right to redline. I can just imagine what I pick up with the porting I did.

Subframe connectors are probably needed when you hit 300+ horsepower at the rear wheels... although adding subframe connectors at any point will definately help your ET's

As for changing over to a Carburetor, it should be simple... get a oil presure sensor to replace the sending unit, make sure it can be used with your guage. You can use a HEI coil in cap design distributor instead, out of an earlier camaro.. these should be easy to wire up. You will need different heads, maybe.. I am not sure if there is intakes available for the TPI heads. I would change the heads anyway.. try to score some camelback heads or vortech heads. As for the rest... it shouldn;t be a problem.. I believe the computer wiring is separate from the electrical system and guages (except for maybe the temp sensor).

I would be able to do it.. but it means a lot of trouble shooting and thought through the process.

It may be good to find a carbureted third gen pice of junk that you can pick up for cheap, use that for a donar car. Grab the carb, intake and heads (maybe) off it, get them cleaned, carb rebuilt and your done... this way you have everything you may need.. like wiring and stuff.

Oh... let me know when you are done.. I am interested in getting the TPI system off of you
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Best Track Time is 14.396 @ 95.71MPH

225.5hp @ 4250rpm (at the wheels)
325.8ft-lbs @ 3250rpm (at the wheels)
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Old 01-03-2002   #15
karfreek
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One thing you have to remember too, these cars are starting to become collectable. If your GTA is in good shape & you plan to sell it in a few years it will not be worth much with that carb setup. I would stick it out, I think solveing the TPI issue would be more benificial in the long run. LET US HELP YOU!


Jay
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Old 01-05-2002   #16
karfreek
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There is an ECM from a 1988 GTA on Ebay for $20. Working Condition

Jay
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Old 01-09-2002   #17
89GTA
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TPI

well, mabey you guys are right. as soon as i build up some more cash ill take it in for a diagnostic. i wouldnt mind keeping the car original. but ive already taken it into my local dealership once a while back and they told me it was the maf..... it wasnt though. i guess ill take it into a different one next time. thanx for all the advice. i know its probly something obvious, but there are sooo many possibilitys.......
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Old 01-09-2002   #18
87 GTA 1
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89 GTA,man you crack me up saying that gta's wuss out at 4500 rpm and carb motors keep goin.Your talkin' a cam change man.It has nothing to do with a carb.The cam is what controls the R's.And a chip with your desired shift point rpm for an automatic is all it takes.But if your going to go carb setup and say the hell with smog,dont waste any time with a chickenshit small block.If I were going to do it, it would get an alluminum headed 427.Any big block for that matter.
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Old 01-09-2002   #19
89GTA
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4500 rpm

hey, thats just what i heard ok.
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Old 01-09-2002   #20
87 GTA 1
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NO dont get me wrong it's true.but the cam decides your power band.
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