Hey, Ive got an LG4 to replace my 2.8l, and its totally complete down to all accessories, even the starter, etc. Anyway, the wiring harnesses are sitting in a box in my garage, and i have no clue what plugs into what. What books/manuals do you guys recommend that I get that will easily tell me what plugs to what? Thanks a lot...


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Mike D. 87 Firebird 2.8L 5speed with V8 swap in the works.

What year is the LG4? I have a Haynes that has respectable wiring harness diagrams up to '84. For the later years (mine was '86), I went to the library and made microfiche copies.

I started with two complete cars, and the only thing I really needed was to figure out how to connect the dash wiring harness to the rear harness (I switched the complete dash harness as well because of all the things that changed between the two years). But, I still learned other things from those two sources.

You still could have problems because tracing a wire color down can be a lot of fun. I don't know of any resource that would be better, though.

You are aware that the V6 tach won't work properly with the LG4? I hope you have the LG4 ECM as well.

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82 Berlinetta, orig V-6 car, now w/86 LG4/TH700R. 2.73 unlimited slip. Cat-back from '91 GTA, Accel HEI SuperCoil. AMSOIL syn lubes bumper-to-bumper. Daily driver, work-in-progress (LB9 w/ZZ3 cam, TBD heads, exhaust, paint, etc.).
57 Bel Air, my 1st car. 0.030 over 396, Weiand Action+, Edelbrock 1901 Q-Jet, Jacobs Omnipack, 1-3/4" headers, TH400 w/TCI Sat Night Special conv & shift kit, 3.08 10-bolt, AMSOIL syn lubes bumper-to-bumper. Best 15.1 @ 5800' Bandimere. Daily driver while Camaro was being put together.

Yup, I have the ECM. Ive got every bit of the required accessories, wiring harnesses, etc. As far as the tach goes, I planned on getting an aftermarket tach with shift light. So you think I should go with a Haynes or Chiltons?

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Mike D. 87 Firebird 2.8L 5speed with V8 swap in the works.

As far as service manuals go, by far the best is a GM factory service manual. They are reprinted by Helms, Inc. You can usually find them on ebay pretty easily. They are year-specific and have excellent wiring diagrams. They are more expensive, tho. A new one can be $80, but i got mine for #20 each on ebay. The extra expense is well worth it for the much more detailed, accurate, and complete information they provide.

If you must go chiltons/haynes, haynes is better in my experience. I have seen some procedured in chiltons that are just plain incorrect or even dangerous.

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82 T/A 305/TH350; soon to be 350/T-5

Excellent advice cfabe. I have just finished putting in a 1988 L-98 setup in my 1985 sport coupe and had to reroute about a dozen wires from the engine harness of the 88 to the 85 setup. I would never have attempted it without both of the GM shop manuals. No aftermarket books will do the job, period. Some of the electrical drawings are part of the large shop manual and some are additional supplements. Make sure you get all that you need. Spend the money or you will be sorry.

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'85 Sport Coupe V6 T5(bought new)Putting in 88 350 TPI/AOD and a bunch of 88 IROC and aftermarket performance parts now.
86 IROC 305 TPI AOD
(selling after Sport Coupe rebuild is done)