Fast355

Just wanted to let you know, my 1997 Express L31 is up and running on a tuned by me 0411 PCM. Still needs some work on the fuel and timing as its a little lean through the mid-range and still has the stock 2002 Express Van timing maps. I think it runs very well for a stock L31 in need of a tune-up in a 6,000 lbs brick.

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GMCtrk

iTrader: (27)

damn, that thing moves very well for a stock 350!

Fast355

The tune knocked over 2 seconds off my 0-60 and over 6 off my 0-80! That is running stock high rpm WOT timing and 87 octane gas. I took off all the torque management, abuse mode, PE fuel delay, altered the WOT fuel enrichement, altered WOT shift points for 5,200 rpm from 4,600, and disabled WOT TCC lockup. Its like driving a different vehicle. I only wish I had gotten more agressive with the timing. I have essentially the same engine in my 1983 with a TPI on top, and it likes substantially more timing than the factory tables on this beast.

I am combing the local wrecking yards, looking for the large intake ducting from a 2001-2002 Express for this beast. I already have a set of Doug Thorley Tri-Y headers for a truck that will fit this chassis. I have the rear catalyst O2 sensors turned off in the tune and will be giving this thing a much less restrictive exhaust/catalyst/muffler setup soon. On my work bench is also a TB with the EGR Diffuser removed.

mds2004

How hard was it to swap the PCM?

Fast355

I am not going to say it was "easy" but it was very straight forward. Many have already swapped and the information is all over the web on various forums. I was able to get my hands on both wiring diagrams and go through everything. I only had to add a few wires to the PCM. You need to have the PCM programmed for a 2002 L31 Express and have the VATS turned off. Mine was a 2wd with a 4L60E. A few of the guys I have seen swap seem to wire up the switch on the side of the transmission to the PCM, but I just run mine with the internal pressure switch. The input is redundant and only used for the Case Relearn. You can perform the case relearn by grounding two inputs on the PCM while performing it. No need to wire up the extra, un-used inputs.