86 TBI swap questions...

[beater_k20]

i've got a friend with an '86 truck, originally came with a weak ass 305. he has since put a 350 in it, and is having problems with his carb on angles. when i was looking at doing a TBI swap into an '86, i was told that the '87 engine harness and ECM harness was a direct plug in on the '86 cab with ESC, even had the proper hole in the firewall for the ECM harness to run through. being a factory cruise truck, on both accounts, the sensor that is needed behind the speedo should be there, correct?

has anybody ever sucessfully installed a TBI setup like this in an '86? any problems you ran into?

 

[btolenti]

I have an 86 with the CCC/ESC/EST system, and swapped to TBI. I used a painless harness though. I heard the same thing about an 87 harness plugging directly in, but never tried it. The truck I took the TBI stuff from was an 87, and the harness was a mess. THe bulkhead wiring header was the same, from what it looked like..... The sensor installed on the back of the speedo is the VSS for the cruise control. There is probably a way to tap into it for the TBI stuff too.....I used an aftermarket VSS that screwed onto the tranny.

 

[dyeager535]

Yes, factory cruise that year will have VSS already. If you got a TBI harness, you might want to grab the VSS buffer, as there are a couple different versions. ('87-89 all operate the same, just different connectors on the buffers in some cases) You can always just cut/splice/solder the wiring, but getting the right connectors is a better bet. EFI will add another wire to the buffer, as I don't believe ESC used a speed threshold of any type.

Not sure about the proper hole, but it would make sense. The ESC is mounted in the same spot as the ECM, but I *think* the holder for the ECM itself is different, just need one from an '87-91 C/K/R/V.

My cab was a diesel originally, you can fit all the ECM wires through the heater wire grommet anyways.

 

[btolenti]

the ECM mount in the 86 will work with the 87 ECM.....

 

[dyeager535]

There were some smaller ESC's used that from what I recall, mounted to the body the same way, but the plastic bracket was "cast" to hold that smaller module.