1227747 to 16197427 Conversion PCM Swap with Wiring Pinout Directions!

[Fast355]

I would have to agree with the people who state this conversion won't make your vehicle run better if you had the original ECM tuned right to start with, but the datalogging is so much better! There is one quirk my van had with the 7747 that has went away now, that I could never get tuned out on the 7747. On cold start at an ambient temp of around 40-50*F I would have to push the accelerator a little bit or it would just flood out with the 7747. If temperatures were colder or warmer than that range it would fire right up with just a turn of the key. Since the change to the 97427 that issue has went away. This could just be an issue with my setup, this engine is far from a stock 350 with more cam than most would consider EFI friendly, and I am sure it could have been tuned out on the 7747 but I couldn't figure it out and the conversion to the 97427 eliminated the need to figure it out. In any case there is definitely something superior about the cold start up routines in the 97427 and it is great having that problem gone after 4 years of dealing with that on daily driving.

GM loves to switch around the wire colors. I recently swapped my L31 black box to a 0411 in my 97 Express using a guide for a 97 C1500. Found several discrepencies with that swap as well.

The 427 swap was very new when I wrote that guide on TGO, very few had done it and the info was scattered across numerous posts and sites. I swapped my 83 G20 first using a 92 G20 harness, followed by th 87 GMC Jimmy 2.8 and a RS Camaro.

Having done 3 different swap, all on well tuned setups, I have to say the newer 7427 has noticeably better driveability than an earler TBI ECM. They ran smoother, were more responsive, responded to changing conditions better and just all around performed better. The real improvement was E-transmissions however.

I will also add I have a 95 G-series calibration I found with the a/c high pressure switch active and I believe the 95 trucks used them too.