final wiring plan

[JD1964]

94 Z28 LT1 / 4L60 swap into 79 Malibu Wagon

Free time is limited but the project is moving forward nonetheless.

In final wiring layout I'll have the PCM and the relay / fuse block on the fender well, battery side to keep wiring as short as possible. I'm using a junction box in that area too which I plan to conceal the soldered splices for a clean look. On the factory F body wiring setup they had one of the PCM grounds going to the underside of the block and others going to the head near the coil. I plan to install a ground terminal block close to the battery, connected to the battery ground post and also a decent size ground conductor running to the engine block / head. The engine will also be grounded to both the frame and the firewall with typical braided straps.

On the grounds for the PCM, (theres 3 or 4 cant remenber), I'd like to keep them as short as possible so can I combine them on the ground terminal block that I install near the battery? Or, should I keep them routed like they were in the factory F body setup?

Thanks

[steveo]

i would follow the factory ground locations if possible.

they experiment a lot with current and resistance and signaling interference at gm and you might not want to have to redo those experiments. the factory harness design's ground points can actually give you quite a clean harness when you get rid of the extra junk and route appropriately.

always think: gm has a motive to save money, so when extra stuff is engineered in that costs more, it might be for a good reason. extra ground points that seem nonsensical were definitely for some kind of purpose. it would be way easier to do a gigantic splice to a ground block (especially since the f-body had a perfectly good ground block right next to the battery)

that said on my trans am i just rerouted them all to a big ground stud that had a single big chunk of welding cable to the block and had zero problems, ran it like that for a year, so if you want to continue with your plan, i'd say nothing will catch fire.

just make sure you dont run the filtered sensor grounds to the block or chassis by accident. i've seen a few people do that by accident because in some diagrams they're labelled as ground, but not intended to be grounded to the engine.

[JD1964]

Thanks for the info. You mention filtered sensor grounds. This link I post has all the PCM pinouts. Which ones in this list are the filtered sensor grounds that you mention? Is it #470?

https://www.lt1swap.com/lt1_pcm_pinout.htm

[steveo]

they are called sensor ground in there

[JD1964]

I just wasted a few hours chasing a no start condition after an intake gasket change out. I solved it an now I feel very relieved. It just so happens that GM designed the IAC and ICM harness plugs the same. I had them reversed. I really was depending on the design idea that each plug is different enough that it prevents incorrect connections. But the engineers at GM missed that one and it threw me for a loop. Anyway, I'm an idiot and I kinda think they are too….

[JD1964]

Come to think of it, I relocated the coil and control module. Had it been in the original location this mistake would have been impossible. I hope I didn’t mess anything up in the electronics. It started right up but I didn’t run it long since it was time to knock off for the evening. I’ll find out soon enough.