just bought a 90 rs with a blown 350tbi truck motor in it.I've done a 3.4 swap into a 90 firebird and a 3.1 into an 86 bird.This is a little different. I can get a 2.8 motor and tranny with harness ecm and all the acceserys.CHEAP compared to the v8's.This is not a restore project or hot rod.It's for a daily driver.Corect me if i'm wrong,If I get the motor compleat with ecm and harness,than this should work right?The vats shouldn't come into play should they?Would I have to change the exsaust from front to rear?

 

Basically read the V6 to V8 swap guides in reverse. lol

So whatever parts are swapped out for that swap, you'll have to swap in.

 

That's kinda what i did.. pulled a 327/th350 and put in a 3.5/700r4.



You'll probably run into small issues here and there but it's 100% possible.


Most of the exhaust can stay, You'll have speedo issues since the 90 and newer use the magnetic VSS. One way around that would be to use the 90's VSS and a 1227730 ECM with a memcal from a 90-92 3.1 Fbody to run the 2.8.. or you could leave the v8 ECM in there to run the speedo and use the V6 ecm to run the engine. A little creative wiring and that should work fine.

 

good stuff,thanks,anyone else got any pointers?

 

u dont need the correct ecm to run the speedo, when we turboed pilsburys care we removed the entire stock ecm and harness and installed a megasquirt.

alls he needed was a buffer box for the vss. i.e u wire the vss buffer box to the vss sensor in the trans and then another set of wires upto the speedo

i think it cost him 15 bucks to get the vss buffer box

 

completely forgot about those, what about the VSS feed to the ECM?

 

https://www.thirdgen.org/forums/v6/5...-3-4-t3-7.html

the diagram for wiring is on this page

 

Get an engine harness for an 86-89 Bird, preferably pre-88. As long as the donor doesn't have the idiot light cluster, you'll have the electronic VSS.

You will need to repin a couple of connectors in the harness, the big one on the driver's side by the brake booster, and there is a small one at the end of the harness on the passenger's side that connects to the dash harness, 2 wires of which need to go into the 15-pin connector next to it.

 

If you were closer (upstate NY) I would give you a great deal on a 88'305 with 80k on it. Complete from the pan to the tpi including the full pulley setup in the front. I bought it to put in my 57 chev car and its just been sitting in my garage for a year and a half. If I don't sell it soon, I'll make it a winter project and restore it 100% and sell it next year. good luck.

 

the vss buffer box will also have an output for the ecm if needed ,2.8 ecm has a vss input but it isnt required

 

Cool, i know the later SD bins ($A1 mask for sure) need the VSS input, they get pissy without it.. which has been my battle lately.

I'm running a 90-92 Caprice "D8B" police interceptor VSS with both the cable and magnetic outputs. My driven gear got munched so i'm waiting on a new one before i can get back to tuning.

 

the 2.8 cars have a vss on the back of the speedo and the ecm gets it input form there ,but i think its only for cruise control as the 2.8 ecm does not have a govener(atleast in the f-body) and there is no real need for speed input on the maf system

 

Um, 2.8 Camaros had the mechanical VSS... Birds with the gauge cluster (as in no idiot lights for oil pressure and volts) had the electronic speedo, no matter engine displacement (post 86). All he needs is a Bird harness with the electronic VSS and the buffer box going with it. Then the choice of ECM is up to him...

2.8 may not have a governor, but the ECM uses the speed input for highway fuel and spark trims.

 

Trust me, i know that optical VSS inside and out. The optical signal runs from the VSS buffer and splits to the cruse, and to the ECM. VSS input like Maverick H1L said is still very important for switching into and out of the idle BLM cell, TCC lockup, highway advance, EGR function, shift light, electric fan perimeters and a few other things.


the 2.8 F bodies may be similar to the 2.8 J bodies in that they didn't put in a speed limiter because the trans physically wouldn't let the car go much faster than the stock tires, suspension and brakes were rated for.

 

There's alot of info in here,it will take my slow brain some time to sort through.The dash isn't much in this old RS.I'd almost buy one of the recked cars I've been looking at and swap out the dash interior wireing engine tranny ecm and all.The carpet is junk and theres no headliner.I need the practice on taking the dash out,cause my iroc needs one put in it and I dont want to practice on that.Would that get rid of the vats?

 

Using a 2.8 harness gets rid of the VATS interference with the fuel injection (VATS also shuts off fuel injection so thieves can't start car even by hotwiring). However, it does NOT get rid of the VATS starter disable circuit. This is, provided that the 2.8 harness isn't from an 89...

You can get rid of the VATS by swapping the dash harnesses, however, you would need to get a speedo cable drive and cable and cluster, and also the speedo driven gear for the cable drive (if the existing gear on the VSS will not swap). And then you get the speedo cable headaches.

Oh, and nobody mentioned it, but you will also need to get either a new instrument cluster OR just a V6 tach, or the tach won't read properly.

 

my 89 had the starter disable circuit, but since i used a Jbody engine harness i just grounded the trigger lead on the relay that's behind the drivers side trim panel. Fires up every time...