Changing the V-6 gas to a Diesel

[fxnelson]

Any feedback on a 1985 6.2 Detroit?
Looking for something that I can afford?
Wife says that it is time to sell my 62 K 1502.

[POWERSTROKE]

My Father-in-law had two 6.2L's. One in a GMC loaded conversion van, about an '82 I think. Then he traded a 4wd Ford Ranger he used on his rural Post Office mail delivery route for a mid-'80's GMC K-1500. The Ranger had the 3.0L gas V-6, and the 6.2L diesel got substantially better mpg, that's one thing they did well. They had problems running over 100,000 miles, various problems. I'd buy two, one to run and a spare. My neighbor had a 6.5L GM diesel in his farm truck, think it was 3/4 ton 4wd, He had a spare rebuilt engine sitting on a skid in his shop in a big plastic bag ready to install. I think it was his original engine. SON drove the truck a time or two, He said my 7.3L PSD ran circles around it, but like the 6.2L, it got better mpg. The 6.5L did make more HP than the 6.2L, think the 6.5L was a bit more reliable too.
I still think a 4BT Cummins would be a good swap into a '60's GMC, maybe a 6BT even. Just a rear axle swap or gear swap gets you great highway gears for cruising with great mpg. SON got 20-21 mpg with his 2014 RAM 250 CTD 4wd mega-cab with auto trans. It ran about 1400 rpm at 70 mph. If he slowed down a bit it got even better mpg. The early 6 & 12 valve Cummins are kinda expensive to buy just an engine. Lots of people want them.

[ilvracn]

my race car team had a couple suburbans we used to pull the trailer with. first one was a 1979 350 gas, no a/c. we upgraded to an 85 with a 6.2 with ac. the gas truck was better for pulling. the 6.2 just didn't have any power. tried to run a/c, cooled for a while, but the floorboards would get so hot it about burnt your feet. also took a lot of power45 mph uphill. ran better after races, with the cool air. the 6.5 diesels are hard to set pump timing, have to use gm scanner, diesel shops in my area don't want to work on them. they tell you to go to gm dealer.
not sure you can find anyone old enough at dealership that knows anything about a 1990's diesel engine. i am a gm guy but i would stay away from a gm diesel, unless you get the 6.6 isuzu duramax.

[George Bongert]

By all means, stay away from the GM 6.2 and 6.5 Diesels!! They were both known to be problematic, underpowered, and unreliable. Go with the GMC TOROFLOW Diesel (if you can find one) or the later 6.6 Duramax Diesel. As to the 6.2 and 6.5 GM Diesels, I had the opportunity to drive a truck equipped with the 6.2 engine, and it was the proverbial gutless wonder. If you're set on going Diesel, there are better options available.

[BobBray]

It all depends what you are going to do with the truck. The 6.2L was originally designed to be a high economy engine with roughly the same power as an early 80's low compression 350 gas. Which it did, more or less. They were fairly reliable if not overloaded, started easy in cold weather if the glow plugs worked right, and did give excellent fuel economy. Like many GM engines, they got better as years went on. Continuous improvements were made, in particular better block and head castings to resist cracking. The 6.5L came out in 1992 with more improvements, including a factory turbocharger option with helped a lot with performance but didn't hurt the fuel economy. Unfortunately, in 1994 GM when to an electronically controlled injection pump that was not reliable with the new low-sulphur diesel fuels that were coming out. It took a few years but eventually even that problem was solved. The later 6.5L's had a better block (cast by Navistar) and those engines were quite good. Keep in mind the U.S. military has been using 6.2's and 6.5's for decades in CUCV's and Hummers. The 6.2/6.5's are a pretty good candidate for swapping if you don't need too much power. They have some significant advantages. First, the engine mounts are the same parts and are in exactly the same location as a 454. These engines have the common 'Chevy' bell housing bolt pattern, which makes it possible to use a very wide variety of both manual and automatic transmissions, including the Turbo 400 and 4L80E automatics. The engines weigh about the same as a big block Chevy, so usually front suspension modifications are not necessary. These engines are almost 'bolt-in' in many GM light trucks. Another big advantage compared to other diesels is that the 6.2/6.5's will turn to 3000 r.p.m.'s, so re-gearing isn't necessary. Many people swapping in Cummins 4BT's run into trouble when they find those engines will not turn faster than 1,900 r.p.m.'s and make a tremendous amount of noise and vibration when they get close to redline. Not much power either. Parts for the 6.2/6.5 are readily available and not expensive, and last time I checked new engines were still being manufactured. Banks still makes a turbo kit for the old 6.2L, because they still sell a few every year. These engines are popular with survivalists because of their reliability, use in military vehicles, lack of electronics, and compatibility with different fuels. They are not all bad. Oh, and one bit of advice from someone who has a running Toroflow: Don't consider one! There are almost NO parts available anymore.

[ilvracn]

if you go with a 4l80e trans, you will need a trans computor for the 6.5 diesel to make it work. i agree the military 6.2 engines were relativly trouble free. those engines are painted red, and can be found in some early 80's pick ups. a friend of mine had one with a red engine, it ran much better than the black painted ones.