hi

i have a 1985 iroc-z with a 305 tpi. the motor uses oil and leaks oil. i would like to replace it with a 350 from a 1991 caprice. i know the tpi intake is different for the two years. can i use the 85 tpi unit and wiring or do i need to use 87-up tpi unit and wiring.

 

You'd want to use the later setup, but you'll need a new computer. If you could find one from a '90 or later TPI car, along with the computer from it, you could utilize the Speed Density system instead of the MAF system.

 

Allow me to elaborate. The vehicle will physically work with the new motor, except that the 4 center manifold bolt holes will need to be elongated and shims used under the bolt heads. However, an aftermarket (or used 87+) base can be substituted. The bigger issue is computer tuning. The 85 computer is pretty stupid, and also does not have as many people reprogramming it as the 86-89 computer has. When I put my 350 into my 85, this meant that I couldn't find any useful help when it came time to burn my own chips, and the car ran absolutely terrible with the stock tune. Rather than try to re-invent the wheel, I swapped to an 86-89 computer and harness, and with it was able to get help from others on the PROM board. I still didn't get enough help for me to feel comfortable making major changes to the chip, but I was at least able to handle the basics, like setting the injector constant, which made a huge difference. My 1/4 mile times went from a 16.1 to a 13.99 with only minor changes other than the ECM swap.

 

are you gonna sell the 85 TPI wiring harness?

 

No. If I sell anything, it'll be the full TPI setup, since I've replaced everything except for the plenum.

 

oh well, can't blame ya.

the search continues...


*EDIT*

wait a minute, I didnt notice this before I posted, but I was quoting Tim Q.
But thanks for replying... if I can't find a harness I might do what you did and upgrade to a newer year.

 

I'm sorry did the caprices come with tpi I thought they were either throtle body or lt1. not sure but I have never seen one with a tpi.

 

TPI was available only in the f-body and in the Corvette. All of the caprices were carburated, then TBI injected.

 

Alright thats what I thought, and I re read the posts I thought he was taking a tpi from the caprice but he is just taking the long block I guess. My other question is as long as he would keep somthing close to the 350 tpi cam wouldnt he be ok with the 85 injection just need new injectors and/or an ajustable fuel presure regulator.

 

I'm not entirely sure. If the 350 is mild enough, he may do ok. A friend of mine swapped a relatively strong 350 into his 85 Trans Am, and ran very rich trying to use bigger injectors on the stock tune. He went back to the stock 19lb injectors and used a fuel pressure regulator to get it close. His car ran much better than mine, which had 24lb SVO injectors with the stock tune. While not optimum, I suspect that if he intends to retain the 85 computer with the stock tune, retaining the stock injectors will be his best bet. He can make some adjustments with the fuel pressure regulator.