It is amazing how the two of us who live below 500 feet are both building trucks with engines that will let us get to and enjoy the mountains. While bringing all our junk along at the fastest speed we can possibly go.
Yes, the Navistar 506 block is the one you want. Better metal for the entire block, smaller outside main cap bolts to keep metal in the block, one piece rear main seal and it looks like the Navistar cast 567 heads. They also have better metal and supposedly better coolant flow.
The heads are where it gets tricky, kind of. GEP made two versions of the Optimizer 6500. Detuned NA which didn't have the piston oil squirters and probably has square stamped pre combustion chambers. The turbo version has the diamond stamped pre cups which are a little bit wider to give more fuel to the more air coming through, it will have the piston squirt oilers and even though the heads are exactly the same other wise. The intake bolts will be at a 60° angle to the head. My pictures in post 88 show how I am dealing with putting the 60° heads on a NA 6500 using a CUCV 6.2 intake. If that didn't work I was going to buy a center mount turbo intake and figure out how to plumb the turbo outlet into it.
GEP lecture over. Now for a turbo lecture. We have nice thick air here in our part of Texas. A stock NA 6.2 or 6.5 has gobs of torque right off idle because of its 21.5 or so compression ratio. No, we won't win a drag race, but they get around pretty darn good until about 45-50 mph. Then the square body starts really acting like an air brake and the engine is starving for air too. Don't forget the 6.2 was designed to have the same power and double the mpg of a 305 gas 2 barrel just a few years after 55 mph became the law of the land. They didn't have to go faster than 55.
But, tooling along at 55 mph is great until you hit a hill and or a head wind. The Banks turbo was made for that situation. At speed down the highway and needing more umph. They flatten the hills great. So good in fact that GM actually offered a Banks option for the diesel trucks. I think I saw a thing where it was a $3,400 option you could check at the dealership and they would install it for you.
Dodge came out with the Cummins a few years after Banks made the Sidewinder, Congress started raising the speed limit bit by bit and fuel went back down below $1.00 a gallon by the time GM came out with the 6.5. GM made the 6.5 with a waste gate so boost could be built at idle and used at all engine speeds. But, they didn't lower the compression ratio so you really couldn't hit more than 8-12 psi without something blowing off, breaking or over heating. Ford went computer controlled IP and lower compression when they did the first 7.3 Power Stroke. (Ford had a mechanical IP turbo 7.3 for about 3 months) Besides starting with a larger displacement engine, it could build more boost and not kill itself. Cummins was high boost from the start.
The few crazy people who still like 6.2 or 6.5 engines seem to think the GEP Navistar cast block and heads are the ultimate. However, even they will point out that a 6BT of any vintage will run away from it. As will the Ford and Duramax. My take on that is cost and simplicity. I saw a few threads were people are putting Duramax/Allison combinations into square body trucks. $10K just to get an engine/transmission and tcase with most of the computers and wiring. Then they have to do coolers, intercoolers, body lifts, Ford front axle swaps, cross members and frame gussets. I don't think I have $10K total in the 7 square body trucks, 14 6.2 or 6.5 engines and assorted transmissions and transfer cases.
The point of the turbo lecture? Treat it as a constant low boost or in need medium boost and very sparse full boost option and all will last a long time. Any more and even a 6500 won't last.
Oh, I really don't mind the thread hijack because you will notice I hijacked it from Joe in the first place.
Back to my project. We removed the 90° HMMWV/4x4 6.5 oil filter elbow from the 6500. I went to spin it over today and no oil psi. This happened with my HMMWV pull out 6.2 now in my M715 a few years ago. I learned then and relearned today that the oil filter on the adaptor will not work hanging down like normal. The outside holes are too close to the O-ring seating surface on the block. A regular 4x2 6.5 or any 6.2 oil filter is what needs to be on there.
Once we got it spinning we did a compression check. 380 was the lowest with 400 or so normal on 7 of the cylinders. #3 which had 0 before the head swap would work up to 100-110, but no more. The cylinder walls looked good and clean when we had the head off. I hope it is a stuck ring or something from sitting a few years that will fix itself. I really don't want to pull it all apart again after just buying new head gaskets, valve cover gaskets, head bolts and oil pan gasket. So we are going to put on the injector lines and try to fire it up. Probably some time next week if all goes well. Then we will recheck compression while of course monitoring temperatures for each cylinder with it running.
