1997 Express 2500 5.0 swap to 5.7 and 411 ECU. In June 2024, I started this project to update my Express to pull my 22 ft travel trailer. I purchased a used 5.7 vortex 880 block # GM replacement crate motor, replaced all the gaskets, seals and parts required by the seller?s 3 year warranty. I replaced the stock cam with a Melling. Duration at .050- 195 int/210 exh, Advertised duration- 273 int/288 exh, Lobe sep.- 112, valve lift- 434 int/462 exh.
My 5.0 exhaust manifolds would not bolt up due to .100 thousand?s difference in hole patterns (so much for SBC interchangeability). Took it to a local auto shop with a copy from the GM service manual showing the 5.7 exhaust system. $400 later, I ended up with a total FUBAR exhaust system (more on that later).
The first time towing the trailer (before the ECM swap), this motor had less power than the 290,000 mile 5,0 motor did. I contacted the seller to return it and was told I had to pay the return shipping and a 25% restocking fee (those costs + all the new parts + another $400 to redo the exhaust system back to fit any other SBC motor = keeping it).
I purchased a 2002 Express 411 ECU and pin list to do the swap. Downloaded the HP Tuners software, took some of the classes from High Performance Academy, Evans Performance Academy, watched HP Tuners YouTube videos & other YouTube videos , and read posts from this forum.
After completing the swap, the motor started right up, idled well and had more power to it. The first scan showed problems with the o2 sensors. B1S1 showed the volts at .037 and B2S1 showed volts at .9 so I installed new DENSO ones with the same results. I purchased and installed an AEM 30-03000 wideband gage and purchased the Prolink for the MPVI3
A week before Thanksgiving, I contacted a local dino shop for help tuning as I was leaving to tow the trailer from Georgia to Arizona to see my sister. He did not have an opening but linked in remotely. He had me unplug the MAF and did a VE tune to get me going. So away I went. The power was pretty good but there was what I would call a stumbling (it was not a miss fire or a knock) when in forth gear at 65 mph. It would go away when I gave it gas and it downshifted. My AFR was between 13,5 to 14,7
The only problem was my MPG was 7.5 (no black smoke or carbon buildup seen in the exhaust pipes).
Whenever I was not on a flat stretch or a downhill hill grade, I kept giving it more gas to keep it downshifted which brought my MPG around 7
After I got to Arizona, I tested my o2 sensors, bought a new o2 sensor (DENSO) with the same results, even when I switched them back and forth. I traced the wires back to the ECM. Verified the correct plugins to the ECM
When I start the engine cold, the volts for both sensors would start at .47 and then B1S1 would drop to .037 and B2S1 would go up to .93
I am wondering if the problem might be the location of the sensor bungs in the FUBAR exhaust. The bung is located about 3 inches away from where the exhaust pipe attaches to the exhaust manifold. Somewhere I read that it should be far enough away from the exhaust port to let the turbulence settle down.
Attached is some of my files. I am planning on heading back to Georgia next week. Any suggestions or help to raise my MPG would be appreciated.
Reply With Quote