Hello,

I have a few quick questions about an engine swap/transfer, specifically relating to the wiring/harness. I'm transferring the engine from a 1987 5.7L TPI GTA (digital dash) into a 1988 (analog dash) that originally had a 305 TBI, and am trying to figure out which engine harness I should use. I have the harness from the 1987, but after reading on here and elsewhere I learned that the 1987 has two harnesses (engine & ECM), while the 1988 only has large one...and now I'm not sure if the 1987 harness will plug into the 1988 body or if the two are interchangeable at all. Does anyone know if the two 1987 harnesses will work with the 1988 body (specifically going from a digital dash to a non-digital), and/or what changes must be made? Or should I look for a 1988 harness?

Any information would be greatly appreciated. Thanks.

Brendan "NinjaNife" West

P.S.
I tried looking up the engine wiring diagrams in my service manual, but there doesn't seem to be an L98 in the book...does one of the other engine models match the L98 in respect to wiring?

 

Use the harness for the body of the car.

 

Okay, I'll see if the harness that was in the body wasn't completely hacked to bits haha. One question though: the body had a 305 L03 in it (the VIN decoder says E = 305 ci V8 LO3 (1988-1992)); should I look for a 1988 L98 harness specifically for my engine, or will the 305 harness work (perhaps with some modification)? I don't know much at all about the difference in wiring sorry

Thanks for the help.

Brendan "NinjaNife" West

 

That may change things a bit. thought they were 2 5.7 cars.

 

Ah..so you don't know what the difference is?

Brendan "NinjaNife" West

 

I know the differences but not in the detail you need. You need 2 service manuals

 

I think I might have a PDF of the 1988 manual, but I'm not sure which engine model is which. The manuals only have information for "LB9/B2L", "LB8", and "LG4" engines (in the Engine Wiring section), and I have an L98 with a body that used to have an L03 (according to the VIN lookup that is). Do you know which of those diagrams relates to each of my engines? Or do you have any idea where I can find more information about the differences?

Brendan "NinjaNife" West

 

You didn't state the '88 was TBI, so the natural assumption was both the '87 and '88 were TPI. I made the same assumption reading what you posted.

You're going to have issues regardless of what you do. The '87 accessories were different than '88 accessories, which switched the AC and alternator side-to-side, and connectors changed. You'll certainly want to use the '87 engine harness, although the TBI harness can be repinned to TPI (I know one guy who did that - one...). TBI used a VSS buffer that TPI didn't use, you should be able to search to figure out what to do about that.

Probably the most knowledgeable harness guy on the Board is Pocket. Perhaps he'll chime in.

 

Yeah I forgot to mention that in the original post; it has been edited to correct it. I always forget that distinction since I never actually saw the original engine, and only "know" what was in it by the VIN...I'm just hoping that nobody swapped the engine type since then lol.

Do you happen to know if the harness connectors (passenger interior and driver in the engine bay) are different? Or are the accessories within the engine bay just shifted around?

Thanks for the help.

Brendan "NinjaNife" West

 

I put my 1987 TPI Motor into a 1988 TBI body. I purchased a 1988 TPI Harness on ebay, since the accessories differ in location.. AC, Alt etc. Also, nice plus.. say goodbye to v-belts!!

I made sure I had both an 1987 and 1988 Helm manual handy as well. Ebay can help.

I ran an inline fuel pump. Just make sure your front cross car harness provides nice power to Fans, ECM, and MAF.

I just took mine out of storage (3 years), and I picked up electrical gremlins. I only noticed chew marks on a spark boot, but I suspect there may be more damage, since engine surges when wipers run. . Time to upgrade mains wires I guess, and give it a thorough checkup.

There is a connector by the radiator (orange 10 ga wire) for cross car. One was damaged on used harness. I butt spliced it. The connector was causing major ECM/driveability issues after swap. So I can't stress enough to make sure, ECM gets good power, as well as MAF, MAF burnoff relay.