Yogi Bear

Got a guy that wants to eliminate the TBI and the PCM on a '90 GMC S-15 4.3L. I suggested the '85-'86 full size with Quadrajet and HEI distributor ignition. Someone else is saying that the timing was computer controlled in '85. Anybody know for sure?

TrickyTransAm

I just scratched all that crap I wrote.

According to RockAuto's online parts guide... It looks like the 85 full size 4.3L has a Vacuum advance, but a 3 pin coil pick up for the ECM.

I know my 86 305 was computer controlled, distributor and trans.
Also....He's going to need something to control the trans in that 90 S truck, otherwise he'll eat his converter.

Yogi Bear

Yeah, I guess that I wasn't too clear, the way that I worded that. I meant that the 4.3 Q-jet came in the full size in '85 & '86, not in the S series.

Not sure why he wants to eliminate EFI. Says that he "wants to clean up the engine compartment". It's in this thread. It comes up about every 4 weeks or so in that forum.

When you say "control the trans in that 90 S truck, otherwise he'll eat his converter" are you talking about controlling the converter lock-up? He knows about the tv cable linkage. I guess that the '85s & '86s had to have some kind of computer to control the lock-up? Does somebody make a lock-up control kit?

Edit: I was typing this while you were editing your original post. I guess that it would be best to get the ECM out of the '85 or '86?

TrickyTransAm

As for the 90, it probably will have a 700R4 or a early 4L60E trans, which needs a puter to control the lockup. I made the mistake on my 86, not hooking that up, and it ground up converter fins and placed them all through the trans causing it to fail.
TCI makes one for vacuum carb vehicles, and there's a few other sources now that have jumped on the bandwagon as well.
I would imagine, if its the same as my 86, that you could use the PCM from the 85, or matching donor vehicle. That would probably be your safest bet. Just double check the pinouts on the trans. Should be a 4 pin connector on the side of the case.
That way it's plug and play with minimal wiring.

....but I'd still choose the MPI injected 4.3L with bigger throttle bodies (same as the LT1 intake)

Yogi Bear

OK. Thanks!

budhayes3

iTrader: (19)

My 85 Monte SS was computer controlled, and the timing was controlled by the PROM in the ECM and the Ignition Module in the HEI distributor. This was a feedback Quadrajet fed 305.

The ECM was located in the right side kick panel...I had to replace mine when it **** the bed on me while doing 85mph on the highway. The PROM was removable and got swapped over to the new ECM.

Not sure if any of this info helps, but it's all I got for ya

Yogi Bear

Every little bit helps. Thanks!