95 to 2000 GM 6.5 liter Diesel

[David Jonson]

I am looking for anyone who is currently running the 6.5 liter GM Detroit Diesel and what they think of it for Overlanding. I am thinking of going this route because you can get the diesel in a half ton. I know they have a bad reputation but would like to hear some honest feedback on them.

 

[Dilldog]

Quite honestly they are decent engines. The 6.2, 6.5 and 8.1 GM diesels are actually Detroit Diesel engines. A lot of people confuse them with the 5.7L Oldsmobile diesel which was a piece of junk. The biggest thing about the little V8 Detroits is that they are guttless, and they tend not to like being hot rodded much. Also be aware that some of these guys look like they have a turbo, but they are not forced induction. Some of these are naturally aspirated but with a high altitude kit, its a 2psi turbo just to help the engine out at high altitude that GM called an "altitude compensator".
I think they get a bad rap because people compare them to the 7.3 Navistar and B series Cummins. Both of those engines are commercial so they are designed to make lots of power and run for a long time. The little V8 Detroits were designed as automotive engines, so they are built lighter and honestly cheaper.

 

[Road]

I had a '98 Chevy long wheelbase Express with the 6.5 that I drove the piss out of all over the United States for both work and pleasure. I drove it for around eight years and regularly put 40-50,000 miles a year on it. It had well over 500,000 miles on it when I retired it, which was more about the body and little things going wrong, though not with the engine. If I'd had something decent to move that engine to, I would have kept it.

I think the only thing I ever had to do with that engine other than regular maintenance was replace the crank position sensor. It was a bit cold blooded when temps dipped below 15-20ºF and liked to have its block heater plugged in. But I drove it through winters in North Dakota regularly, where it gets to -26ºF for days at a time.

Keep good batteries with a high CCA in it, and make sure the glow plugs are all working right, and I'd drive it anywhere, anytime.

I liked the GM van platform so much I went straight from the '98 6.5 to an '08 GMC Savana with a 6.6 Duramax, which, with the more modern electronics, starts easier and quicker in extreme cold. Last year before DEF, so I'm going to keep it long as it runs. It's at 410,000 right now.

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[David Jonson]

Thanks for the replies, | am not looking to "hot rod" it so that isn't a problem for me. I am looking for decent fuel economy and something with no emissions. The overall goal is to fix the bugs it may have and take it North to Prudoe Bay then south to Patagonia.
Thanks again for the tips

 

[Dilldog]

If set up properly the 6.2 and 6.5 can get some good fuel millage. I would just say once you get one just do a full fuel system overhaul and I would be tempted to pull the valve covers and inspect the cam lifters push rods, etc, then pull the pan and check how the rods and mains look. Just be aware that they are a pre chamber engine so extreme cold effects them much more than a direct injection engine. Also I would get good at changing glow plugs. If I were to use one as an overland set up, I would set up 2 or 3 extra batteries hooked up to a block heater and oil pan heater, that way no matter where you are or how cold it gets you can still get it started. Just dont use starting fluid. Its hard to use properly and impossible on your own, and can seriously damage the engine. I have always used WD40 to help the old pre chamber engines start. The propellant in WD is propane. Propane is a catalyst for diesel combustion and not per say a fuel by itself in a diesel engine, so it just helps the fuel being injected combust thus it is much easier on the engine. Starting fluid can load up in a cylinder and because it is a "dry fuel" can cause cylinder wall scuffing but most importantly it combusts with such force it can break rings turning an engine into an "addict" if it is not sprayed through the air cleaner while the engine is being crancked.

 

[Dakota Houligans]

Decently reliable. But lacks power. Although since your looking at 1/2 tons I'm guessing its more about mileage and longevity than power.

 

[David Jonson]

Decently reliable. But lacks power. Although since your looking at 1/2 tons I'm guessing its more about mileage and longevity than power.

That’s exactly what I’m looking for, longevity and mileage. It’ll be carrying a four wheel camper or similar and at most pulling our Off Grid Pando. Every diesel around me is programmed or built up which I don’t want. Another reason for the 6.5, people have left them alone

 

[David Jonson]

If set up properly the 6.2 and 6.5 can get some good fuel millage. I would just say once you get one just do a full fuel system overhaul and I would be tempted to pull the valve covers and inspect the cam lifters push rods, etc, then pull the pan and check how the rods and mains look. Just be aware that they are a pre chamber engine so extreme cold effects them much more than a direct injection engine. Also I would get good at changing glow plugs. If I were to use one as an overland set up, I would set up 2 or 3 extra batteries hooked up to a block heater and oil pan heater, that way no matter where you are or how cold it gets you can still get it started. Just dont use starting fluid. Its hard to use properly and impossible on your own, and can seriously damage the engine. I have always used WD40 to help the old pre chamber engines start. The propellant in WD is propane. Propane is a catalyst for diesel combustion and not per say a fuel by itself in a diesel engine, so it just helps the fuel being injected combust thus it is much easier on the engine. Starting fluid can load up in a cylinder and because it is a "dry fuel" can cause cylinder wall scuffing but most importantly it combusts with such force it can break rings turning an engine into an "addict" if it is not sprayed through the air cleaner while the engine is being crancked.

I was thinking of adding a webasto heater to it for the cold. When I find one it’ll for sure be getting outfitted with new everything, thanks for the tips on glow plugs. That’s great advice

 

[Dilldog]

I was thinking of adding a webasto heater to it for the cold. When I find one it’ll for sure be getting outfitted with new everything, thanks for the tips on glow plugs. That’s great advice

Those are sweet, if you need any help with them let me know. I have worked on those guys quite a bit, and I went through factory Esbar training which is what the Webastos are a copy of. Depending on how cold it gets you may want to rig up a fuel heater too, and I highly recommend getting an oil pan heater rigged as well as warm oil will really help those guys start in the cold.
One big thing to keep those diesel heaters running well is to let them run for at least 30 min. once a month. If you get a bunch of smoke that doesnt clear up run it on kerosene to clean it.