im looking at swaping from TBI to TPI. is there any reason for choosing a mass-air over a map system. the car is a 91, and i hope to add a supercharger after i recover from the TPI conversion. just didnt know if one was more flexible than the other.

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91 RS
91 GMC Syclone

 

The best advice I can give is don't do it. It's such a pain in the butt, it isn't worth it. I started this swap in December and now my car is still sitting at my parents' house. I knew it would be a big job, but I didn't think that it would take me more than a few months. Now I feel like I'm farther away from finishing than I was when I started. And it isn't because I'm inexperienced either. I have had a GM tech and a Lexus Tech who has worked on SBC engines since he was old enough to turn a wrench helping me on this project and it still isn't finished. Yeah, sure, people will tell you that it's easy and that you can do it. I don't know what their secret is, but don't count on this board for help, because everytime I ask a question about how to finish my car, I have gotten very incomplete responses, if I get a response at all (of course, I'm sure this post will get some responses, but where were you guys when I needed you?!). Anyways, enough of the soap box-- get a 350, keep your TBI system, and it's plug and play (with a few modifications, of course, but nothing like TPI). You'll proably be happier, and your car won't catch on fire like mine did. If you still decide to go for it, and you want a complete run-down of the problems I ran into so you can learn from my failures. Let me know. Otherwise, unless you are independently wealthy and have plenty of time and money to pay someone who REALLY knows what he/she is doing, stick with whatcha got. BTW- If you decide to do the swap, go MAF.

 

jroy i'm in the middle of putting a 89 5.7 tpi in to my 91 tbi firebird.can you give me a run down of what problems you ran in to?

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1991 banditt2 #130 of 600
Project 350 TPI Banditt II
http://www.street-dawg-racing.cityslide.com
http://photos.yahoo.com/tonysams72
http:/discussion-board.com/GreaterCincinnatiFBodyAssociation/

 

No sweat, here they are in no particular order. Some of these are still UNSOLVED as we speak and have been since January. Some of these might be things you never thought of. I'll include the approximate prices so that you can see the 'hidden costs' of the TPI swap (Hey, maybe I should write an article!):

1) Fuel pump-- The engineers at General Motors really outdid themselves here. Since in their infinte wisdom, GM decided not to install an access hole which could have been conveniently located in the trunk (*#$%! morons!), many claim that the rear end must be dropped in order to drop the fuel tank. This isn't necessarily true. With some fanagling, a friend of mine and I managed to accomplish removing the tank in a few hours. We did have to cut the cat-back that I recently had installed (boy, was I sick to have to do that!!) After this is complete, you are on your own as far as installing an out of tank pump, as there is no retro-fit kit that I know of. I mounted mine where the fuel filter used to sit by cutting a few inches of the steel line, replacing it with hig-pressure hose (pricey) and some clamps. You will have to cut some steel fuel line long enough to reach the bottom of your tank 'cause the fuel pump is gone (unless you like to fill up your tank every few miles). YOu will also have to rig up a filter between the pump and the fuel rails. I used the stock rubber fuel line in the engine compartment that has the threaded fittings, and found some fittings I could use. Pretty pricey fittings, by the way. Oh yeah, and don't forget to get a new fuel tank seal from the dealer. Price: mostly free, but cost a lot of time $30 for the fittings, $10 for the fuel line, about 7 bucks for the seal:

$50 + cost of installing cat-back ($50+)

2) Wiring harness-- its own set of problems altogether. If you have a salvaged one, no telling what wires/relays/connectors are fried. You should probably trace all of your leads for shorts BEFORE putting it in to save yourself some headaches. and if you happen to cross your TBI and TPI harnesses, guess what? Your car catches on fire like mine did. You could buy a 'painless' harness, but this wouldn't necessarily prevent the two harnesses from crossing somewhere. The ultimate solution is to buy a custom harness from FIS or another company, which will run close to or more than 500 bucks depending on your application.

Cost: several hours of tracing shorts + a new wiring harness $300-$500


3)VATS--- gotta either bypass it (see tech articles for pretty cool how-to-steal thirdgen Camaros write-up), or have a custom chip burned, which, if you plan on doing anyway (good idea) is no big deal. You could also install a push-button start:
Cost: custom chip 300+ dollars; or the price of a resistor (a few pennies) and having to explain to the insurance company how your car was stolen so easily when it had a VATS (assuming you have full coverage). You can always get The Club ($19.95). If it makes you feel better.

4 VSS-- big nightmarish sneaky problem that the evil GM engineers devised to make our lives a living hell!! This sends information about your speed from the rear of your tranny to your speedo, from your speedo to the ECM. Problem: the VSS in 86-89 sent a 2-pulse signal (don't ask me. I have no idea what that means), while the 90+ had a four pulse. Consequently, you have to buy some sort of adapting gizmo that allows your VSS to send the signal to the ECM. Not sure about the cost, probably not more than half a C-note. Don't know how to solve this yet.

5) This is really minor, but still kinda frustrating-- the 87 uses a one-wire oil pressure seending unit, wheras the 91 has a two-wire. Not sure how to solve this yet.

6)Throttle/TV cables. Unless you can find these at a junkyard (Not likely. I waded through a foot of mud in Briggs TX searching for these), you'll have to order them from GM. Your stock cables will be too short $45

7)Misc: you should probably get new intake bolts, gaskets, thermostat, etc. 30 bucks.

8)You'll have to rig up a fan switch 10 bucks.

This is all I can think of right now. If I think of anything else I'll let you know. This is just to show you that you are probably going to spend a couple of hundred bucks more than you planned to, probably more, in order to get your car running RIGHT. If you're like me you're thinking; gee, I spent about 500-600 bucks on this TPI system plus at least $200 more on the 'hidden costs', plus I need a custom chip (most likely) at $350, plus my car may/may not have VATS (priceless), plus all the other nightmares, headaches (read F-U-N)
Gee that's over a thousand bucks (at least!!! probably more if you're buying a new wiring harness) you could've sank into your current system, but wait, then it wouldn't be TPI, would it? . Oh, I forgot, this is only if you want a bone-stock TPI system. Let's not get into what kind of cash it takes to upgrade. Not trying to discourage anyone, I just can't stress enough that this is a major project that can seriously **** up your car if you don't do it right. Take your time, always, ALWAYS have a fire extinguisher around, and above all, try to have fun! That's what it's all about. I hope that this helps some, and will try to get others in on the post. IF any of you have solutions to the above probelms PLEASE for the love of GOD help me! My car as we speak is a several-thousand dollar battleship anchor!

Cheers,

James

 

Oh yeah, another thing I forgot. Banditt, for your application, you'll probably need to relocate your battery to the trunk so that you'll have room for the air cleaner: $50 from Summit (Hey! That makes it only $45 with the discount!)

 

Really it's not all that bad.
Look here: http://24.1.139.249/images/122000/DCP_0108.JPG

Took all of 5 hrs. to complete using the TBI harness.
E-mail me for details. delcruzen@hotmail.com

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Chronologically challenged. But still kicking!
'92 CAMARO RS
305 TBI 5/spd (now TPI)
B4C Alt.
'69 camaro-BB/Lenco,1050 dominators, /Pump Gas/no drugs 8.97-150+/3200lbs.
SoCal Thirdgen F-Bodies



[This message has been edited by Dyno Don (edited April 08, 2001).]

 

Really it's not all that bad.
Look here: http://24.1.139.249/images/122000/

Took all of 5 hrs. to complete using the TBI harness.
E-mail me for details. delcruzen@hotmail.com

------------------
Chronologically challenged. But still kicking!
'92 CAMARO RS
305 TBI 5/spd (now TPI)
B4C Alt.
'69 camaro-BB/Lenco,1050 dominators, /Pump Gas/no drugs 8.97-150+/3200lbs.
SoCal Thirdgen F-Bodies

 

alright well I think I have solved this one, there is a company called stealth conversions that sells VSS's for TPI engine swaps. they have a cable driven 4 pulse unit for my '88 . Anyway, here is a link to thier VSS page hope this helps.

sorry forgot the link

http://www.jagsthatrun.com/Pages/Spe...eedometer.html

[This message has been edited by camaroguy99 (edited April 10, 2001).]

 

First of all, I bought an AC Delco fuel pump from GM for $115. It came with the gas tank seal and everything. All I did was swap the new fuel pump in where the old one used to be. For the fuel filter, I just got a stock replacement. The TBI fuel lines are 5/16 which is plenty.
Second, everyone makes changing the fuel pump harder than it actually is. I peeled the carpet up and cut a hole im my trunk. I ordered some zsus fasteners from Summit, $15, and used some stainless steel I had laying around, plus some rubber weatherstripping foam from Western Auto to make an access panel. Now I have access to my gas tank in minutes, plus with the carpet covering it, no one knows it's there.
Third, the wiring harness was no problem at all. I ripped it out, sent it to Howell, $350 and two weeks later I had a TPI converted harness with all the factory hookups. No fire here.
Fourth, My vatts problem was solved with a custom prom.
Fifth, I'm using the 88 vss in with my '90 computer. I'm going to look into this four pulse unit. My car runs fine now though, maybe I can pick up a little with the new one.
Sixth, I'm using my '88 oil pressure sending unit, no problems here. Plus, I have a whole complement of Autometer guages, so I'm not worried.
Seventh, my new throttle and TV cables cost $30 from Mente Chevrolet.
Eighth, intake bolts, gaskets, and thermostat is a given. You should change no matter what type of induction swap you are doing.
Ninth, I'd rather have my fan on a switch anyway than have the computer control it. But, with my Howell converted harness, that was no problem.
Yes, it can be pricey. Especially if you build a new motor like I did. But, it's worth it. I LOVE my TPI and I'd take it over throttle body any day.
By the way, Don't go with MAF. If you're starting from scratch go SD because it gives you more tuning options in the PROM.
JRoy91RS I'm here if you need help. My email is in my sig.

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'88 IROC TPI 355, '69 truck 4-bolt, fully balanced, 9.75:1 compression, fully ported '70 truck heads(for now), Harland Sharp 1.6 Roller Rockers, Comp Cams CS 252AH-12, ported '86 TPI converted to speed density, Crane AFPR, Flowmaster 3in. exhaust, Edelbrock TES headers, all emissions equipment is still intact, plan on burning my own chips, many more mods and parts on the way as time and money permits =(
Best E.T. with TBI 305: 16.11 @ 82mph
Haven't been to track with new motor
If you have any questions on converting from TBI to TPI email me at jdkchevy70@yahoo.com
In memory of Dale Earnhardt, I'll miss cheering for that black #3 on raceday!!!

 

Hey! I'm confused, there website makes no sense. I have an 88 camaro that was TBI, and I converted to SD TPI. What do I order to make the VSS the correct 4 pulse.
BTW, can I just order a '90 vss from GM. Will it fit in my 88?


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'88 IROC TPI 355, '69 truck 4-bolt, fully balanced, 9.75:1 compression, fully ported '70 truck heads(for now), Harland Sharp 1.6 Roller Rockers, Comp Cams CS 252AH-12, ported '86 TPI converted to speed density, Crane AFPR, Flowmaster 3in. exhaust, Edelbrock TES headers, all emissions equipment is still intact, plan on burning my own chips, many more mods and parts on the way as time and money permits =(
Best E.T. with TBI 305: 16.11 @ 82mph
Haven't been to track with new motor
If you have any questions on converting from TBI to TPI email me at jdkchevy70@yahoo.com
In memory of Dale Earnhardt, I'll miss cheering for that black #3 on raceday!!!

 

you can't just order the 90 VSS. Our speedo (1988's) are cable driven. I think I heard that it's the only late thirdgen that is that way. So since a 90 VSS would be electronic it won't fit our speedo. I think it's the #4VSS on thier list. It took me a while to figure it out though. They do need a better site.

IrocZ88,

BTW, I'm doing the exact same swap. ('88 TBI to 91 SD TPI) Any pointers you would be willing to post would be great. thanks.

Jim

[This message has been edited by camaroguy99 (edited April 12, 2001).]