GM 6.5 diesel trucks?

In reply to Curtis73 (Forum Supporter) :

I'd rock one in a heartbeat if they hadn't all rusted away up here.

Curtis, you turned your 6.5 TD to 4500? The injector pump governor was set at 3400 rpms on mine. 

I'm a bit surprised by the 6.5 love here.  There was an entire industry built around block girdles and such to keep them from breaking in half...

Deboss Garage did a good video on the 6.5: 6.5 Detroit

Curtis73 (Forum Supporter) said:

Civilian, yes (as in Hummer).  Military, (as in AM General) not that I have heard of.  I know that AM General is still making new 6.5s to put in the Army and Marines HMMWV.  From the wiki page:  

 but the 6.5 (6500 Optimizer) is still produced by AM General for the HMMWV.  

• 1994 - present AM General HMMWV

Kind of makes sense, since the Duramax is an Isuzu engine, and the military is funny about having to rely on other countries' industry for its vehicles.

81cpcamaro said:

Curtis, you turned your 6.5 TD to 4500? The injector pump governor was set at 3400 rpms on mine. 

Well, I didn't, but it's an easy mod.

Some guys claim 5500-6000 is possible on a stock assembly, but diesel + 6000 rpms = not much time for fuel to burn + diminishing returns.

Common tune/governor for good burning time and stock reliability is around 4750.

81cpcamaro said:

Deboss Garage did a good video on the 6.5: 6.5 Detroit

He mentions a really good thing in that video... that you can pretty commonly get 450-500k out of them.  The B50 life number for even the venerable Cummins is 350k.

For those of you who aren't diesel folks, engines (particularly diesels) have a B-life rating.  Usually B10 and B50, corresponding to the mileage at which the average engine needs a major overhaul... as in, at least bearings and rings.  That is to say, if the B50 number is 350k, that means that 50% of those engines needed an overhaul by the 350k mile mark.

6.5TD Pros:

• It will likely out live you and cockroaches
• one of the best of the truck diesels for MPG.  Empty with 4.10s you can expect low to mid 20s
• pretty quiet and low on NVH by comparison to the 2000s diesels (but not as good as 2010s diesels)
• easy and cheap to modify for more oomph.
• bang for buck.  No one thinks they're viable anymore so their value has tanked
• great parts availability

Cons:

• they make "enough" torque in stock form
• Old school IDI tech does have its limitations for power without rolling coal
• Gotta move the PMD before it cooks

If you're not looking for big power, they really are hard to beat.

I'll be honest... the 66 Bonneville has been waiting for a Duramax for a decade now, but Dmax prices aren't coming down.  A 6.5TD swap is starting to look more and more probable in that car.

In reply to Curtis73 (Forum Supporter) :

Kind of like an LD50 for rings.  Neat.

350k is still kind of depressing.  I took apart my 400k mile VW engine and the bearings still looked great.  It smoked a bit of oil but the PCV system in the 5 cylinders was horrid at best, the crankshaft windage blows oil AT the crankcase breather, and the cylinder head tends to fill with oil because the drainbacks are insufficient.  The turbo Volvo whiteblock I redid had rod bearings that looked pristine.  I replaced the mains for peace of mind more than anything.  Pistons got the ring grooves cleaned out and the oil return holes unplugged and got put back in with the original rings.

In reply to Pete. (l33t FS) :

Yeah.  A nice nebulous number that should be followed with YMMV 

I drove one today, I don't think I will buy it because it was generally pretty rough for the price (dents, failing clear coat, drivers side door handle broken and door wouldn't close, filthy interior with drivers side door panel broken/not attached anymore, door loose suspension, covered in spiderwebs, etc).  Didn't seem worth $5500. 

One weird issue I couldn't figure out was that it would run fine at part throttle but full throttle it would stumble and bog really bad.  Bad lift pump maybe?  The owner said it has recently been changed.  Also, it idled pretty high (like 1100 rpm) when I first started it, and if I slowly reved it to ~1500 it would take a long time to go back to idle.  Is that normal?   Other than the one I looked at being a pretty rough example I liked how it drove though.

It sounds like that one is a hard pass. That is not normal running behavior for a 6.5. They may have changed the lift pump, but after running without it for a while, this would damage the injector pump. 

Yeah, I don't think there was anything wrong with it that would be impossible to fix, but it would cost more than buying a better one to begin with even at half the price.  With truck prices right now it's probably worth more to someone who wants a marginally functional truck than to anyone who would want to fix it.  I think the owner had spent quite a bit of money on repairs too.  I will add them to my list of craigslist searches and if I come across any better ones I will go look at them.

In reply to Tk8398 :

accompanied by big clouds of black smoke?  If so, restriction in the fuel system which could be as simple as a fuel filter, or lift/injection pump.  I know it sounds counter-intuitive, but the 6.5TDs will open the wastegate to stop boost when it senses defueling or low fuel pressure.  I had taken Dad's 6.5 cross country for our RVing honeymoon because my 88 TBI truck at the time was on its last legs.  It took me a while to figure out why his truck would suddenly bog down and belch clouds of black smoke.  Turns out the filter media was faulty and had fallen off and jammed in the hole.

Seemed counter intuitive that it would go black smoke with less fuel, but its because the PMD opens the wastegate to defeat the turbo.

Still, $5500 would have been too much if that truck were running perfectly.  They should idle at 800, and (given the compression) they should snap back to idle fast enough that it rocks the truck a little bit.

There was too much traffic where i was driving it to see for sure if it was smoking a lot but that sounds right.  That one probably needed a new injection pump along with all the other issues from the sound of it.  I will keep looking for a better one, I don't think I'd pay $12k for one like people seem to be asking for a good one, but if prices ever come down I think it would work for what I want.

They are passed over completely by the Duramax fans and Cummins powerstrokers would never look anyway so they go for very little money here. I see them all the time for under $5000 for nice 4x4's and lots of them are under $3000. 

I bought this one for $400 and went through it completely this summer. It has new tires, brakes, transmission flush, pmd, exhaust, lift pump and a new dash (showing 90 km!) For around $4000.00 total. My son had been driving it daily with no issues.