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1973 GMC lt1

Discussion in 'GM Powertrain' started by Jay04, Jan 18, 2013.

  1. Jay04

    Jay04 New Member

    Guys I have a problem that I have not been able to figure out. I had an 84 cutlass that someone had transplanted a lt1 out of a 94 caprice cop car in. They used the same wiring harness out of the caprice with the transplant. Motor ran great in that car. I knocked the transmission out of the car and pulled the motor and tranny and sold the car. I purchased a stand alone wiring kit from painless for that powertrain. I have a 1973 gmc 2wd truck that I decided to put the powertrain in. When I did so I did not use the original transmission, I just used the 400 turbo that was in the truck. I first used the same electric fuel pump that was in the cutlass. The truck starts idles and revs perfect, but when you go to drive seems like it's lacking a lot of power, and after running for approx 20 min engine would cut out and pop at around 4500rpm, the more you drive the truck the worse it gets, like a lack of fuel. It will never die but gets very doggy and hard to accelerate. But if you shut it off and go to restart it, it will fire for a split sec and die like a vapor lock. I thought it was a fuel issue so I hardlined my line to and from the tank all the way to the fuel rails and put on a bigger higher volumer fuel pump from holley. The motor has a constant 42lbs of pressure. The fuel pressure regulator appears to be working properly. I have put a new coil on the motor with no change. So I am out of idea's for now and hoping someone on here can help. I don't know if not running that 4l60e tranny will effect how the computer/engine performance if at all? It is the original computer out of the 94 caprice.
  2. tbplus10

    tbplus10 Epic Member Staff Member 5+ Years 5000 Posts Platinum Contributor

    The 4l60E is computer controlled, how did you compensate for the trans inputs to the computer?
    That could be the issue.
  3. Jay04

    Jay04 New Member

    I have not compensated for the inputs. Would i need to get my computer re-programmed to solve the input problem, or would I be best having the 4L60e rebuilt and put that in the truck?

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