Hello all-
I have a 91 RS that no longer seems to have any rings or valve seals left in it's 305 TBI. I just picked up a complete 89 IROC donor car with a 350 TPI in it, and had a few questions about the swap before I dive in. I know for a fact that I need to pull the following out of the donor:
Motor
ECM
Engine Harness
Fuel Pump

My questions are as follows:
1. Running the 89 ECM with a 91 dash, will my gauges still work? Can I just patch my VSS buffer into the 89 ECM?

2. Can I leave the current 700R4 that was on the 305 in the car? OR did something change on those between 89 and 91 that will prevent the TCC from talking to the ECM?

3. VATS... Will it still function properly? Not sure if it is dependant on the year/featureset of the ECM...

4. PROM... can I use the stock 89 PROM that is currently in the 89 ECM? OR will I need to burn a new one?

I've searched the net and several forums for the answers, but have yet to find a clear answer to these questions. Thanks for any input!!! It's very much appreciated! Hope to return the favor someday!

-Brad

 

TTT for ya, I need to know the answers to this too.

-Rippin

 

1. Running the 89 ECM with a 91 dash, will my gauges still work? Can I just patch my VSS buffer into the 89 ECM?

The 89 ECM will plug in fine to your underdash harness. Your guages will function fine. You will need the under hood wiring from the donor car (all wiring from ECM to under the hood and the accessory harness if you don't want to cut and splice yours). Your TBI VSS will function fine with the 89 TPI ECM. 90-92 TBI and 86-89 TPI used the same pulse width for the speedo. Just in case you were curious, 90-92 TPI was different.

2. Can I leave the current 700R4 that was on the 305 in the car? OR did something change on those between 89 and 91 that will prevent the TCC from talking to the ECM?

Your tranny is fine.

3. VATS... Will it still function properly? Not sure if it is dependant on the year/featureset of the ECM...

Yes, 89 ECM PROMs had VATS, and it will work in your VATS equipped car.

4. PROM... can I use the stock 89 PROM that is currently in the 89 ECM? OR will I need to burn a new one?

The stock 89 PROM will work fine.

 

Excellent, Thanks for putting my mind at ease Cdartz! Hoping to start on her this weekend, so your advice came just in time =) Thanks again! Hoping I can give something back to the board after I complete the swap and she starts and runs *crosses fingers*

-Brad

 

No problem.

 

cdartz:
How long did it take you to do the swap? Was it hard? Did you know exactly what you were doing or were there some things that you kinda winged?

-Rippin

 

On my 90 myself and two friends did it working a couple days a week over the course of about 2 months. We worked a lot of late nights getting things done. I did my research first, but of course you always encounter things you don't expect. Luckily for me one of the guys I mentioned is a former mechanic and a wiz at electrical wiring. Things both myself and the other guy couldn't do the mechanic friend made quick work of.

 

I am doing a 305 to 350 tpi swap and I have an 85 TA and the motor is coming out of an 88 Formula

I know that the dash is totaly different will this still work

or do i need a 350 computer & chip out of an 85

 

I assume your 305 is also TPI. Both 305 and 350 TPI systems use the same ECM, just the PROM is different. However, 1985 cars did not use the same ECM as in 1988, or the same MAF. the ECM part number used in 85 was only used for that year. 86 through 89 used the same ECM (still MAF, but a different part number MAF), and 90 through 92 used another ECM (these are the SD cars). You have a couple options. You can keep your 85 ECM and MAF, but you will have to have a custom PROM burned to account for the extra 45 cubic inches of engine displacement. You will also need 22 lb injectors. A better choice is to use the ECM from the 88 Formula. With that ECM you can run a modified PROM from an 89 350 car (you have to have one burned with the VATS turned off since your car doesn't have it)(the benefit of the 89 PROM is that is does not use a cold start injector, but instead modifies the pulse width of the 8 main injectors to compensate. It's a better system), or you can simply use the stock 88 PROM with no modifications. Using the 88 ECM will require you to use a MAF from 86-89, and don't forget to use 22 lb injectors as well. If you do use the later ECM you will either have to use a later wiring harness or modify yours a bit. If you don't want to spend the money for larger injectors you can burn your chip for the 19 lb injectors. As far as the dash being different that doesn't really come into play. It's not like you have to change the underdash wiring.

 

Thanks cdartz

So I really want to keep my 85 ECM How hard is it to burn my own prom (I know nothing about the process) and would I modify my current 85 prom or the 88 prom.

Richard