I'm helping a friend do a TPI swap to his 1991 RS. It currently has the stock 305 throttle body motor. He has a complete tuned-port setup from an 89 IROC (which is MASS air). If he uses the (non-speed air ECM and ECU), will his 1991 (factory) guages work? Or, will he have to use a speed density TPI setup and a 1991-1992 Z-28 ECM? Any other problems to look out for? Any help would be GREATLY appreciated!!

Thanks again guys!!

Mike

 

This is a tough one to answer, unless someone with a '91 Helms and someone with an '89 Helms care to spend time posting the pinouts of C100 and C207, the two harness to chassis connectors.

C100 is on the driver side firewall just below the relay bracket, C207 is under the pass side dash near the ECM.

When I swapped '88 TPI into my '82 chassis, the oil pressure gauge required relocation...it was in C207 on the '82 and C100 on the '88 harness. Lots of other pin moves I had to do to get the engine and chassis harnesses to match up and no way to know if your '89 and '91 harnesses are similar.

It's cheaper to have an existing harness repinned by Howell EFI or most other TPI vendors, as opposed to buying two Helms guides and doing it yourself.

 

an 89 MAf into a 91 SD it's not a plug and play kind of thing.it's best to have a 90-92 harness and ecm.
but it can be done

 

But, I dont think the 91-92 ECM has provisions for things like the (cold start injector) etc.. Would a 91-92 ECM and harness would with the 87 IROC Tuned-port stuff?

 

is it 89 or 87?
either way it will work.if you use an 87 intake with a 90-92 SD ECM and harness you will need to plug up the cold start ports at the runner and the back of the driver side of the fuel rail.
you can have the 87 or 89(which ever you have)converted to a SD harness like i did.get ahold Leonerd Sparks at
www.chevythunder.com
what i had sent him was an 89 MAF harness,ECM and PROM.and he sent me back the converted harness,SD ECM and SD PROM for less than $200.also he was very helpfull with helping me trouble shoot the problems i was having.

 

If you use a sd harness all gauges will work fine except speedometer and odometer. You will have to bypass the vss buffer that tbi cars are equiped with. A guy posted how to do this bypass a few weeks ago and my speedo finally works now.

Good luck with the swap. If it is your first time like mine plan on taking your time. I am finally finished after about 3 months. (took a while to work out all the glitches)

 

91banditt2 - Why would I have to plug up the cold start injector? Couldn't itself be a plug if the injector isn't connected to the wiring harness?



Mike

 

yes the cold start inject would act as a plug but i wouldn't want it there if it didn't need to be there.

 

I know for this older TPI setup that I need pre 87 heads (non center bolt). The question I have is: If I have a 1991 roller / 1 peice rear main short block, would pre 87 heads work with a Hydraulic roller cam 'ed (new style block)???

 

Yes


but make sure that if you're not running self aligning roller rockers that you DO have a set of guide plates, and visa versa.

 

I just swaped one in to my car all i had add/change a few wires to the c100 connector (engine side)

added a ground wire to C7 of c100
(usage vats gages etc)

added a ground wire to F8 of c100
(usage sir)

connected pin f on the alternator to G8 of c100
(car wouldnt charge without it)

add vss wires to E4 and D4 of c100

removed orande wire (under hood light) from interior harness side (c207 connector pin m) located under dash next to computer. The 89 wiring harness has a ground going to that location and kept causing my accesory fuse to blow as far as i could tell the 89 wiring harness has no under hood light