New Update
Sorry for the delay in updating, I don't get much time to be on the computer except when life slows down during the winter!
So, after selling my C20 tow rig, the Tahoe was called in to do more towing duties. The stock 1/2 ton 6.5L hardware left a lot to be desired, with a restricted EGR intake manifold, questionable air filter box, and smallish exhaust. The stock radiator and cooling system wasn't up to the task of towing, either. I had managed to get my hands on a 1997 C3500 parts truck, which granted me access to the non-EGR intake manifold, better air filter assembly, and dual thermostat housing. I also pieced together a better flowing exhaust system.
First up on the exhaust upgrades - 3" turbo downpipe that was not smashed and dented like the factory pipe:
Also included was a mandrel-bent crossover pipe for the turbo that did not have all the wrinkles that the factory pipe did:
Both of those pipes were made by Flowmaster, purchased from Summit Racing. I then fabbed up a 3.5" exhaust system (no cat... former owner had already 'misplaced' it) with a Donaldson muffler that I purchased used online. (No pics of the rest of the exhaust system).
I swapped on the HD intake manifold. Here is the upper manifold; original EGR manifold on the right, and free-flowing HD intake on the left:
Free-flowing HD lower intake installed:
Upgraded 1997 air filter box (original box used a flat panel, new one is a round filter):
To keep an eye on everything, I installed an EGT and boost gauge I purchased from Kennedy Diesel:
I then ditched the problematic vacuum-controlled turbo wastegate and installed a Turbo Master mechanical wastegate:
http://www.heathdiesel.com/turbo-master-gm96.html
I was then able to remove the factory belt-driven vacuum pump, since I no longer needed vacuum for anything else. I had to get a shorter serpentine belt, and simply unbolted the vacuum pump.
The installation of the Turbo Master caused a new issue: the factory ECM did not like the fact that it could no longer control the boost, and started setting the CEL and going into "limp mode" anytime I tried to tow. A little research found that I needed to modify the ECM to fool it into thinking everything was okay. I had Kennedy Diesel build me a custom chip:
https://www.kennedydiesel.com/detail.cfm?ID=37
It helped, but still set a CEL and limp mode once in a while. I sent it back to Kennedy, who programmed it some more, and that finally fixed my issues. Now I could tow at full throttle without throwing a CEL or going into limp mode. I set the Turbo Master to 15 psi max, and the Kennedy chip also increased fuel and timing to give me a small bump in power. EGT's max out around 1150 when towing long grades.
This provided the reliable power I needed, but now I had a problem with cooling. The 6.5L is known to run hot, and mine was no exception. The factory 1995 cooling setup included a large radiator, but only one thermostat. In 1997, GM upgraded to a higher output water pump, and a dual thermostat housing to provide more water flow when the 'stats are open. (Sorry, no pictures of this upgrade.) I still haven't installed the high flow water pump, but the dual 'stats helped a good bit. But honestly, the best cooling upgrade was absolutely free: The stock fan clutch does not kick the engine fan on soon enough. You can purchase aftermarket fan clutches, but I simply bent the round, metal thermal spring slightly which forces the fan to engage at a lower temperature. It's absolutely perfect! Now the fan kicks on much sooner, keeping the engine from getting too hot.
One other item I upgraded was the fuel filter. The stock filter is pretty small and dinky, so I replaced that with a Racor system; I installed two liquid-filled pressure gauges that I plumbed before and after the filter. This lets me know if the filter is getting clogged:
I now had a very reliable and healthy 6.5L turbo diesel to tow my camper and Jeep around with.
Casey