OT 6.5 Chevy diesel

6.5 chevy diesel any good?

My Uncle swore by them. He had 4 in his fleet that had over 300K miles on them without opening them up. Hard to argue with that kind of success. He was a fanatic on maintenance.

I have a 98 with a 6.5 and 185K. I bought it from a 1 owner at 140k. Only think I did was replace the fuel pump driver for $300. Some people have no luck with them but mine has been great. They are NOTHING compared to the new diesels but I dont need the power of the new ones. Mine will pull an 8K trailer without a problem. Any bigger trailer, or on a real regular basis and I would want more power.

Can't be all bad... are in the Humvees protecting this country! I have one with 190k on her and no problems. Previous owner did relocate the fuel pump driver which is a must. Not the greatest engine but nowhere near the worst. I'd recommend them to anyone who can do a fair amount of mechanical work anyways.

good in there day. i got 400,000 on mine and its still running.original injectors, heads, and rings. had pump o/h @ 110,000 and not touched since.

I have to chime in on this one. We had a 3500 four door dually the last year of the 6.5 I believe it was 2000, and it was not a success story. The mileage, power, reliability, cold starts etc. well lets just say NEVER again. It was a very nice pickup I will give it that. We now pull the same trailers with cummins diesels and I am in LOVE!! I believe the oldest one we have a 92 will wear out the next pickup I put it in. Ironically it could be a chevy!!

1997 3/4t currently at 235,000 miles, runs excelent, no problems..

You'll get answers all over the place on this question. Some had nothing but problems with 'em and some never had one problem. Myself, I have a '98 dually 1-ton with about 230K on it and it runs as good as ever and pulls better than most 6.5's ever thought of....'course I added an intercooler and upped the boost a bit. Granted, it's in NO way even close to the pulling ability of a Duramax, Cummins, Powerstroke, etc....but for the price difference, I'm gonna keep it 'till it quits.

One little side-note. The average life-span of a 6.5 in the Humvees in Iraq is less then 2000 miles. Our military has been searching for a better replacement engine for years.

From Military Defense Magazine, 2004:

"Army Ponders New Diesel Engine for Humvee
Trucks," notes that maintenance nightmares have been experienced in Iraq because engines
regularly break down and often must be replaced after only 1,000 to 2,000 miles of operation.
Much of the blame for this is placed on the bolted-on armor protection that adds weight to the
vehicles"

I have 92 3/4 ton that has 217,000 on it. I use it almost daily. It is strictly a work truck. I wish it were a little stronger on towing ( we have alot of hills) but it has been extremely reliable. I had to pur a clutch in it and a lift pump or transfer pump I can't remember what it's called. It starts good when it's cold and it's not too bad on fuel.

It is the lightest V8 diesel ever made in the US, and was never intended for severe duty. Detroit Diesel originally was asked to design it as a direct-power replacement for 305 gas engines - with fuel mileage in mind - NOT heavy use. Started out as the 6.2, then got bored to 6.5 with an added turbo, and then added electronic fuel controls. Military 6.5s retain the mechancial fuel systems.

I've gotten over 200K with several, and 520,000 miles on one. But, that's NOT with heavy use.

The Ford 6.9 and 7.3 is built much better, and the Cummins 5.9 better yet.

6.5 has a light block that has cracking problems in the main-bearing webs - and sometimes #8 cylinder. Main bearing cap-bolts were downsized from 12MM to 10MM in later engines to keep blocks from cracking. Also has a cast-iron crankshaft that sometimes snaps in two. Also uses a timing chain instead of gear drive. Also has light cylinderheads that are prone to cracking and most have no hardened seat-inserts. From 1994 and on, 6.5s had awful problems with electronic fuel controls. Many later got updated and somewhat fixed.

Compare to a Ford-IH 6.9 and 7.3. Much heavier block, forged steel crankshaft, gear-drive cam and injection pump, and much heavier heads with hardened inserts. 6.9 and 7.3 was also durability tested and rated for HD use. Pretty good considering IH built if from an existing truck gas-engine format. Made off the MV404 and 446 gas-engine basis.

I won't even mention all the specs on the Cummins 5.9. It's a true long-stroke truck engine and worlds different than the aforementioned.

GM 6.2s and 6.5s weigh 650 - 700 lbs.
Ford IH 6.9 and 7.3s weigh 900 - 950 lbs.
Cummins 5.9 weighs 1,036 lbs.

Thanks everyone, you helped me decide. Thanks again!!

No company has EVER built a V configured diesel that was anywhere near as good as an inline. They all had problems. Not CAT,not Cummins,not IHC/Navistar,not Detroit Diesel.

If you want a diesel in a commerically built pick-up then there is only one choice. a Dodge with a Cummins.

Uh, think you got it backwards... if you want a commercially built diesel then you buy a Dodge with the Cummins. The Dodge's are not commercially built trucks.

Military hasn't been looking for new engines at all, maybe complaining about them but if anyone would be looking it would be AM General. Would cost too much to re-tool and stuff a different engine into the current Humvee. It cost too much to fit the Duramax into the Humvee and both are GM engines. Would be cheaper to build a whole new vehicle based on a different engine than re-tool. And I think there is still a contract between AM General and the military to supply the Humvee's. Would have to check on the length left.

Yes, they certainly were looking. I've got a stack of paperwork here about it. You don't discover something isn't cost effecitive, until you look into it. They decided that using an alternative engine would not be cost-effective. They also researched the possibily of getting a more reliable fuel injection system and that too, was not cost effective.

Cummins makes a repower kit to replace GM 6.2s and 6.5s. Comes with an adapter plate and a 3.9 liter turbo-diesel. Works fine and has been used in many trucks in the US. Not cost effective though for the mililary.

What was done instead of an engine replacement program, was to come up with a much heavier built 6.5 that is now used in Humvees. Also marine use. It's the 6500 Optimizer. Navistar has done some of the block castings and the engine is put together by General Engine Products. Block is heavier with added nickel content. Heads are much heavier. Some cranks can be custom-ordered in forged steel.

The 1K-2K mileage life average takes into account the vehicles that are destroyed. However, the military now runs on "One Fuel" which is JP8. Anyone who knows much about diesel systems will tell you to never run straight #1 diesel especially long term due to the lack of lubricating ability for the pump. JP8 is pretty close to Kerosene. Now figure all the extra weight added by the extra armor, running on JP8 which easily has only 2/3 the btu content of #2 diesel, that makes for engines pretty much running flat out in temps well above 100 with the A/C on.
From what my brother has told me after being on 3 tours in Iraq, when they fuel with JP8 they typically have a top speed of 40mph. If they fuel with #2 diesel, they top out about 65mph.

Then what are they then ? They sure aren't one of a kind customs !!!!

When the Hurcules plant was operational in Canton, Oh, The gov't was seeking a bolt-in replacement. And that was 15-20 years ago.

These engines were garbage from the get-go. In response to the one fellow, no one has ever built a good FOUR STROKE V8. The two stroke detroits were a very simple, easy starting, reliable engine. The overhaul cost per cylinder is ridiculously low, and could be overhauled by a monkey in a monsoon.

About -

"JP8 which easily has only 2/3 the btu content of #2 diesel"

That's incorrect. JP8 has about 6% less BTU energy per gallon as compared to #2 diesel.

JP8 has 123,069 BTUs per gallon.
#1 diesel has 125,207
#2 diesel has 131,207

In regard to statistics about engine failures - I can't say exactly how the numbers are calculated. I've bought over a dozen military 6.5s that were sold as unrepairable. Came over here by the 1000s in large shipping containers. Every one I took apart had serious problems - but some could be fixed.

Thin fuel and high heat don't work well in any distributor pump. It's the distributor section of the pump that has problems, not the high pressure pumping portion of the pump. The military had many problems with A1 tank fuel, and less with JP8. But, not enough less. There's no work around that anyone's found other then converting to an inline pump. That's not feasible on the 6.5. Stanadyne came out with an "Arctic Fuel" upgrade kit that was supposed to make the pump more tolerant of thin fuel - and it didn't work.