What's up guys? Well, I have a '90 Firebird 3.1 V6. I'm going to be doing an engine swap from a '90-'92 350 V8 (once I find the donor car)...
For the wiring, do I just deal w/ the part that comes out from the passenger side in the engine bay? Or, do I have to pull out the whole cable, and plug in the V8 Harness all the way back into the ECM on the Passenger Side Kick Panel? Do I have to do any other wiring other than w/ the ECM? Do I have to go under the dash on the Drivers Side for any reason? Will the ALDL work the same w/ the V8 as it did w/ the 6? I know my best bet would be to use the whole harness from the donor car. (Just clean it up, etc.) This would only consist of the Harness that plugs into the Firewall from the Passenger side? I'm not sure if a plug is there, or it just goes in the firewall and all the way to the ecm. I shouldn't need to touch any other wiring, correct?
I posted the wiring question in the Motor Swap forum, but was advised to try "here" for more help on the wiring issues involved w/ my setup. Any help would be appreciated.

Thank you very much!

 

First, before you go any further, you MAY find it easier to just start with a V8 car. Doing a swap from a V6 to a V8 is a lot more involved than just getting the motor mounts and dropping in a V8.

The tranny must also be changed as your V6 tranny will not work. The bellhousing is different and they are not built to take the torque of the V8. Also, you most certainly have a "One Leg Peg" in the rear.

When you start adding up all the things you will need to look at, starting with a V8 car with a worn out 305 starts to make a lot more sence. If you V6 car is in good shape you will find that you can easily sell it for fairly close to the V8 and now your swap (assume 350/383 for a 305) is a lot simpler.

But eventually, you'll also need to look at the tranny and rear if your V8 is potent. The stock trannies and rear ends are not that tough, even on the V8. But you don't have to deal with it immediately, like you would on a V6 swap.

With regards to your original question, for the wiring, I recall looking a an ECM/Harness differences between the V6 & V8. You have a MAJOR advantage, as your car uses the same ECM as the SD V8 cars. In fact, you can reuse the MAP sensor!

As I recall, you can reuse the harness for 98% and the V6 may actually use more pins/wires than the SD V8 TPI cars. You will need to change some of the leads (obviously) but as I recall, the V6 harness is very easy to adapt to the V8.

I had my conversion chart done in Excel. If you have Excel, I will dig up the conversion for you and e-mail it. You SHOULD try and find a copy of the 1991/1992 wiring diagrams for the V6 and TPI cars. Post a message for Vader on the General Tech Board, I am sure he can find one for you.

Just let me know if you have access to Excel, and I will e-mail you the wiring conversion chart.

But DO give serious consideration to JUST buying a V8 car to start with.

 

Thanks for the information Glenn91L98GTA. Well, I've done extensive work to this car as it is. I have a HUGE Sound System, I sound proofed the whole entire thing (floor pans and all)...Fourth Gen Power Seats...ABS Headliner, Overhead Console w/ custom switches, Custom Alarm (rolls windows up, locks doors, etc.)...Neons underneathe...Body is in perfect condition (just restored it about 3 years ago)...That's basically why I want to keep this car. The V6 is rebuilt and bored out, but, I just want the PUNCH that a built up 350 would give you. I was reading that it's not as big of a hassel as it may seem to be to swap it out, but who am I to talk? Well, if I could use my MPFI '90 V6 Harness, then, that would save TONS of work (I'm assuming)...

Glenn...I DO have access to Excel...the conversion chart would be a GREAT help.

If there are any other concerns that I should be aware of, please let me know in advance. I think the other main thing is trying to find a 5.7 Bird or Camaro that's good for a scrap car (but the block isn't cracked, etc.)

Thanks again guys!

 

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https://www.thirdgen.org/techbb2/sho...03#post1498703