I just got a 5.7 TPI from a 91 Z28. The engine and tranny are in excellent condition with 80,000 miles (car was totaled). I got the motor, tranny, radiator, all accessories, computer, and rear end.

For two days I've read the previous threads and couldn't find what I'm looking for. First of all, there are two objects that I need to know what they are.. see pics.. The white part is located around the rear axle and from what he told me it has to do with the vent portion of the gas tank. There black item I just found sitting on top of the motor.

Also, I understand the speedometers are different (one is mechanical one is electric). What is the procedure I need to do to get the speedometer working? Is it as simple as just installing the piece (gear) from another tranny?

Has anyone of us ever gone thru the trouble of taking a pic of every connector we have to connect and giving a description of what it is..? The guy that removed my engine disconnected everything, but he didn't label anything. I just need to know "how many are there?" Basically a "one is for this and it's located here, one is for that and IT's located there" etc..

Lastly, the guy told me the rear end is different from mine. The calibers appear to be made out of aluminum and the disc appear to be a little larger than mine. I was under the understanding 87 and 91 rear ends were the same. What are the different differentials that this rear end could be..?

Any help would greatly be appreciated tremendously ....

Stone

 

The white thing looks like the vent valve for the fuel tank. It looks like the hose nipple is broken off.

The black part is the "A.I.R. diverter valve", that routes the air flow from the "smog pump" to either the exhaust manifolds or the catalytic converter.

The electrical connectors are almost fool-proof, meaning you have to work pretty hard to connect them to the wrong thing.

The rear disk brakes changed between '87 & '91, with the later ones generally being considered superior. Also, '87 had 26-spline axles, while '91 had much stronger 28-spline axles.

You can swap the rear parts from one transmission to the other to get the mechanical speedometer working. However, the ECM needs that vehicle speed sensor (VSS) signal that came from the transmission in '91, but came from the back of the speedometer in '87. You'll have to rewire that to get the '87 signal to the '91 ECM.

 

I have both computers, the one in my 87 is still connected. Do you think it would work with my 91 motor and tranny?

Stone

 

Yes, but...

'87 TPI was mass air flow (MAF). '91 was speed density (SD, or MAP).

'87 had the 9th injector, '91 did not.

'91 TH700 is a little better overall design.

What you might consider:

Put the '91 engine in, but use the '87 TPI hardware (including plenum, harness, sensors, ECM, MAF, etc.). If your '87 is a 350, that's all you need to do. If the '87 is a 305, you need to use the 350 injectors, and get a knock sensor and module for a 350 (the '91 used a different knock sensor). And, it would probably benefit from a 350 PROM.

Put the '91 TH700 in, but swap over the output shaft gear and speedo driven gear for the cable drive. If you use the '87 TPI system, you won't have to do any other modifications/rewiring.

 

wow.. I have the old 5.7 (87) but it has a blown head gasket and hasn't been used in 9 years. I found my 91 5.7 in a car someone got totaled so I bought the motor and tranny and he threw in a bunch of other stuff from the 91 Z28, radiator, rear end etc. My 87 IROC body is in NO RUST or previous accidents condition, so I'm trying to save it from the crusher.. I just picked up a 96 Z28 set of seats, front and back dark grey vinyl in real good condition. Can't wait to get it running. Just trying to build something fun to drive and realiable. This is my 5th IROC... and my last.

 

The '91 longblock with all of the '87 hardware and sensors, and the '91 tranny with the speedo stuff swapped over, should be the ticket, then.

Have at it!

 

hey there!! Hope all has been well with you. Came across a 91 Z28 this weekend, 5.0 auto. Decided to install my 91 5.7 TPI in it (like the updated interior and that crazy rear wing has grown on me). See any issues I might be facing now..? Motor and tranny came out of a 91 Z28 going back into a 91 Z28 only difference is old motor is a 5.0 mine is a 5.7

Stone