High Compression Ramblings On The GM 6.5 Diesel

June 23 2019

New Article Series!

Hey all! I just wanted to introduce a new article series that I will post occasionally, the "Parts Bin".
It's a series that you commonly see in many auto magazines and one I personally always looked forward to reading.
Every now and then I will show something that is new for our trucks, something you all may not know about, or just something that has caught my eye.

If you have any ideas for good stuff to share, let me know.
To get to the Parts Bin link, just go to the home page and scroll down towards the bottom.

First part up? Quality rebuilt DB2 pumps from John at Quadstar!

Cummins Swap!

Sept. 9 2018

Oil out of the tail pipeYou're Having A Bad Day When You Have Oil Blasting Out The Tail Pipe

Two days ago I set out on a trip that was going to keep me gone for about two weeks or so. Just traveling around the northwest to see friends, look at property to buy and hopefully start an interview series that I want to do with certain stars in the 6.5 world. 

And yet, two days later here I sit. At home. In front of my computer. Talking to you. 
What the hell happened?

What happened is something that has likely happened to many people and that is an engine failure.

What? An engine failure on an engine that was built specifically to last with (mostly) all the right parts like mine was?

Well I guess the 6.5 does suck. Stick a Cummins in it!

See how easy that was? And that's what has happened many, many times.

Nobody likes to be left on the side of the road. And when it does happen, you're usually pretty pissed. And when you're pissed, you aren't usually thinking perefectly straight. Ever heard "don't make decisions when you're angry!". But that's what we do. 

So, The Story...

Towing the 5200lb RV with Moby. It was a 93* day but with all the standard cooling mods and the Twisted Steel Performance coated Champion radiator, she was running fine. 65mph up a short, very mild grade and right after cresting the hill, BAM! Loss of power, smoke, noise, kids screaming, cats and dogs fighting, pure pandemonium, my trip has ended. 

I pulled over off the freeway and was enveloped in steam/smoke. I saw the temps raise to 225* for just a second, and the oil pressure dropped from 42 or so to about 25 but that was when I dropped it out of gear, so everything was really fine there.

After shutting her off, I popped the hood, got out and walked around to the scene of despair and carnage. Ok, I'm being pretty dramatic but I refer you back to the beginning of this story, that's what we do. 

But then things got really bad. I glanced back towards the tailpipe and saw a 6' stream of black oil that had been puked out of the tailpipe. I refer you back to the picture at the start of this post.

Ok, time to panic. 

I set about trying to arrange for a tow but couldn't get anything so late on a Saturday so instead, I set about settling in for a long peaceful night on the side of a busy freeway.

Thank God for data streaming and a gallon of gin.

So as I waited for two very cool brothers Miguel and Jose' from Dayton Wa. to come haul my happy ass back to safety and comfort, I had some time to get cerebral on the whole thing instead of freaking out like a 13 year old girl who just got called out on Facebook for wearing the same top as Jenny. 

And it worked, I figured it all out.

And when I say I figured it all out, of course I mean that I called Will and he pretty much figured it all out. 
Another junk 6.5? Crap heads? Crappy head stud install? Nope, that's not what he figured out, sorry haters.

Let's see, we have...

  • An Optimizer motor with ARP head studs and Fel-Pro .010 gaskets, so better heads with very slightly lower compression ratio and quality gaskets with good clamping on them.
  • A-Team turbo for lower cylinder pressures.
  • Water/methanol injection for lower cylinder temps and resistance to detonation.
  • No indication of water in the oil. 
  • Truck starts right up and runs with no noises and good oil pressure except missing on a cylinder. (or two)

What could have happened to a well set up motor pulling only a mild load on a mild day?

My first clue came when I looked at that fat black streak on the ground at my tailpipe's feet the next day.
It was dry. Rubbing the black rocks only brought up carbon. If it was oil, it would still be wet so that meant it was water and carbon blasted out. And it didn't TASTE like oil (just kidding, ew).

Mmmm k

Here's the last piece of the puzzle that set the solution in Will's insane brain...

I have a fitting in my heater core line that had gotten up against the downpipe, melted a bit, broke, and spewed the coolant all over the place. That's where the steam and temperature spike came from.

Broken fitting on downpipeBroken Fitting Melted On Downpipe and Blew Coolant All Over

And Will realized that's where the cylinder miss came from too. 

A sudden massive loss of coolant means loss of system pressure. Loss of pressure means instant boiling off of the coolant which means a very fast temperature change against the metal of the cylinders and heads which leads to cracking.
And all that means that your motor hates you. Asshole.

I likely have a cracked head or cylinder wall that is feeding coolant into the cylinder causing the miss, the top radiator hose to instantly get hard from compression getting into the coolant system, and water to spew from the tailpipe. 

So here's my second apology to the haters, the 6.5 wasn't to blame so suck it! : )>

The saddest part here is that it absolutely didn't have to happen and was completely all my fault. 

You see, I have temperature probes at my #8 cylinder, at the top radiator hose, and at the bottom radiator hose in addition to the stock location. And I can move the probe pick ups for my two digital Autometer gauges to any two of those locations. I had them at the #8 and stock locations to see the difference but had crawled in there to move them to the radiator for data collection on the Twisted Steel Coating of the radiator. When I did that, I had pushed that fitting in the hose out of the way and against the downpipe but didn't push it back. BINGO! I'm a bonehead!

All my fault. 
All unnecessary.

So the situation now is; 

  • If it's only a blown head gasket (not likely), I'll pull the heads, change the precups out to diamonds like I've wanted, and use Victor-Reinz head gaskets (.010 again) to slap her back together and hit the road.
  • If it's the heads, I'll get p400 heads and have Chris at Twisted Steel Performance do his full temp coatings on everything, use Victor-Reinz .010 gaskets, slap her back together and hit the road.
  • If it's a cracked cylinder, I'll get another Ted's Trucks Optimizer take-out, change the pre-cups to diamonds, use Victor-Reinz gaskets, and then you know what I'll do? I'll hit the road. 
Exhaust in the radiatorYou Should Not, I Repeat, NOT Have Exhaust Coming Out Of Your Radiator


In conclusion, I again refer you back to the beginning of this tirade. 

6.5 failures are frequently blamed on the 6.5 and rarely the owner. Failures in life are rarely blamed on the owner. 

So, when you have problems, sit back for a day or two with a tasty adult beverage of your choice and think about it. More importantly, call up someone smarter than you like I did, but figure out what the real problem is. If the motor was built right to begin with (that part is important), you'll likely find that the problem was either owner-operated or from some component that had nothing to do with the 6.5 platform to begin with.

Take care of your motor, it'll take care of you.

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