Tbi swap build thread

[rfmaster]

Originally Posted by BigBlocksRule

Yet another newbie...
I have an '85 dually that I want to sell the engine and tranny out of and install a freshly rebuilt Gen 6 454 along with a 4L80E. I have a '95 that I'm using the cab and other parts for a different project, so I can strip the computer and harness out of it, this truck originally had a 350 and 4L80E. I have access to an '87 truck that I can snag a baffled TBI tank from and plan to install a transfer pump to move fuel from the unused tank into the one with the TBI fuel pump. I also have sourced a set of gauges from a '91 so I can use the electronic speedo.
What am I overlooking?

Welcome to the thread.

Donor drive train: 95 ( 2wd?) 454 + 4L80E (rear end ratio + tire size)
Recipient platform: Dually 85 (2wd?) (rear end ratio + tire size)

The 85 did not have 4L80E as OE - probably 350-700R4, 350 -350C or 350 -THM400 . You must keep the 454 + 4L80E + PCM as a unit to make swap simple. Make sure to take DRAC or VSB module from 95 donor as well. Take a look at VSS it should be where the old speedometer cable used to bolt into trany tail shaft.

I am not familiar with 91 speedometer - being electronic then it will take one of the DRAC outputs (4000 ppm) to drive it. Depending on rear end gear ratio/tire combination DRAC reprogramming maybe required to get speedometer indicate correct speed.

Late 454 TBI systems - 94 & 95 model years used higher fuel pressure over traditional 9-13 PSI used by SBC and earlier BBC TBI. Starting in '94 the 454 TBI fuel systems went from 9-13psi spec to 26-32psi. Use TPI or Vortec spec fuel pump in the 87 baffled tank:
AC Delco#: EP241
GM#: 25116163

Feed fuel line from the gas tank to the TB inlet should be 3/8" - use steel line with SAE 30R9J rated flexible lines. Original fuel line might be marginal due to its age (it was not designed for high fuel pressure operation - carburetor fuel pump operated in lift mode)

//RF