My apologies if this has been asked and answered, my search skills are not what they should be.

I'm putting TPI on a 77 Corvette and I have the factory harness and the rest of the parts from a 91 GTA. Are there any instructions on how to modify this harness?

Thanks in advance,

Contrail

 

i think there is some sort of book you can buy from summit/ebay for tpi swaps..hope it helps

 

the easiest way is to use a painless harness.

 

Factory harness will work fine if u have one in good shape.

U need to get complete engine and dash wiring diagrams for your vette and the 91 bird. (I'm assuming u want to make the dash work as well)

Its not too bad to too. Go thru everything first and photocopy the diagrams and make notes and pencil wiring drawings for stuff you have to add. Work it all out before you even put it in the car.

Than work from there.

Going to have to defeat the VATS in the chip however :-)

later
Jeremy

 

Go ask a guy restoring a classic if he has the original wiring in his harness. Probably not.

Dont get me wrong you could do what 3.8 is talking about and it might work. That is how I started out turning my 3.1 car into a tpi car.

This took a whole lot of work and headaches reading diagrams and tracing wires. I got good at it but to this day I would rather deal with on wire than to customize a harness that is getting old.

Now back to my original point. the harness you are putting on that vette that I am sure you love is 15 yrs old. it has gotten hot a cold so many times something is bound to have gotten brittle.

For just over 300 dollars your car can have a brand new harness that just runs your engine. the instructions are easy to follow and much eaiser that splicing a old tpi harness with a 77 vettes harness.

3.8 I am not trying to put you down but I am not sure that you have tried both options as I have. The painless harness is stand alone all you have to do is ground it give it power and connect to things such as the brake switch.

If you want to go this route and have questions pm me as this is getting to long.

 

Thanks for all the replies. The harness I have is in remakable shape for its age. Very flexible and not hardened at all. I still have all the looms, also. I have a Prominator so defeating the VATS is not an issue. Most of the folks around here have said the same thing about getting a Painless harness. I'm gonna put it all together in April so I still have time to make a final decision. I have everything traced and accounted for as far as sensors and leads to the guages, I just need to know how to incorporate a fuse block, and where to get my power. Also, I need to get a setup for the Check Engine light. That's all I have left to do, so any advice in that area?

 

I've done it both ways.

On TPI, turbo 6, LT1 and LS1 cars :-)

If the harness is in good shape, wire it like a TPI car and be done, easy if you got the diagrams.

Stock engine harness doesnt have hardly anymore wires than a painless.

I wont ever screw around with a torn up/brittle harness.

Thats not worth it once u start having to rewire large sections or buying multiple weatherpac connectors(junkyardsa a good source as long as you can find good ones)

How much stuff u need to put into the fuse block?

In the fuse block your going to need constant 12v and switched ignition.

I would suggest running a fuse box from an exisiting(if can handle additional power) fusible link or running a new one for protection purposes.

I would prolly run new power leads and fusible links for the injection side of things.

Chk engine lite can be made by simply following the factory wiring for the chk eng lite and adding it on anywhere u wish. Guess your easiest would be to incorporate it to the ALDL connector since you'll be adding it in anyhow. Could put it into the dash as well if u have any dummy lite openings available, just takes a little more work

I might be wrong on one or two things, its been like 2 yrs since I've had to seriously play with a TPI harness.

later
Jeremy

later
Jeremy

 

I've got a 4 slot fuse block, two for the injectors, one for the computer and one power input. 10amp fuses for the injectors and ECM, and 20 amp for the power lead. As it happens, I do have an empty socket for the Ck Engine light. I think I'm gonna go with the harness I have for now and if I start having issues I'll just bite the bullet and get a Painless setup. I have replaced the stock alternator (63 amp) with a 100 amp unit, and I'll run a direct line from the Batt pos. to the the power input on the fuse block. Alternately, I could run off the B+ wire on my existing distributor. The grounds are already in the harness and will bolt on the rear of the heads just like the GTA it came out of. ALDL is already wired in and I reused a connector to snap it into the engine harness. So, am I on the right track? I've got all my guages figured out except the tach, but I'll either figure that one out, too, or come back and ask.

Contrail

 

Sounds like you have a good handle on things.

Just make sure anything that comes off the battery or hot from the starter is fused or has a fusible link. A $5 piece might save a car from melting down :-)

Always play it safe and solder and heat shrink everything as you get the circuits figured out.

I've wired a fair amount of accessories and harnesses in thirdgens. first place I go when adding, modifying, etc is to look it up and see how it came from the factory, that way when I go trouble shooting I can follow the manual(with some wiring color excpetions obviously)

later
Jeremy