6.5 pros and cons

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My '93 C2500 is a 6.5, last year of mech. injection. That's the major reason it's been so reliable. 2nd engine and the first one wasn't worn out at about 200 k miles. Got a good deal on a year 2000 mil. surplus AMG made new engine. With the piston oil squirters and the later and stronger block. Put a bigger turbo on it, (A-team) and the dual thermostat/later cooling upgrades. Turned up the DB2 pump and put an intercooler on it with a dual compressor outlet temp./eng. inlet temp indicator. The intercooler made all the difference and drops the eng. inlet temp. between 90-130 degrees at full boost of 13 psi which is all I'm going to feed it. From all the accounts I've read over the years, the 6.5 does_not_hold up at all with boost over 15 psi. Better mileage with the I/C and noticeably more power, lower eng. temps. I've got about 70 k on it now and no bad problems. You couldn't give me a 6.5 with the electronic injection though. And be sure to add the diesel fuel additive. The Stanadyne inj. pumps don't like the ultra low sulfur fuel. Just my .02.
 

smdk2500

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Well the guy took my offer of 1500. In the next few weeks ill get the pmd relocated and check out some of the other things mentioned in this post. Like I said it won't see a lot of towing duty. I will look into that exhaust system that was mentioned. When i drove it i didn't hear any leaks but when driving by buildings on my way home with it i could hear a couple. When i get some more time I will post up some pictures.
 

smdk2500

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Here are a couple of pics. One when i got it home and the second is after the ugly topper was taken off. Gunna have to take it to work so i can get the running boards taken off.
 

Marc Elkins

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After Old blue (in my prof pic) was destroyed in an unfortunate head-on collision, I started my search for another GMT400. I, too, went for the 6.5L search too. I work in the fire service & we had a support vehicle with the Detroit in it that lasted over 500k w/just a PMD relocate & general everyday maintenance. Agreed, it is a turtle, but it is a strong turtle. I have purchased a 1999 K2500 Suburban (pics to come) that was once a U.S. Army MP vehicle for a fair price w/lots of extra parts from Army Surplus. Most of the upgrades have been completed & I just did the vacuum pump delete with manual wastegate. I have no complaints at the moment. She does well on the highway & the hills with an average fuel consumption of 18-20mpg. I hope for many miles out of this & wish you luck with yours. I look forward to seeing your updates as they come & hope to share mine as well.
 

busaben

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I really liked my 6.5, the major problem I had as well as many others is the pmd, and the lift pump switch, knowing how to bypass the switch in an emergency is a big plus, and relocating the pmd is a must, you can buy an extension harness and another pmd and leave the current one as a spare since they are booger to remove. Also they respond real well to a cheap diamond eye exhaust kit
 

smdk2500

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I was looking at it the other day and the pmd has been relocated but it is to the top of the intake. I will get it moved into the bumper. When i get my other 95 ran low on gas and start pulling the good parts off it I will start a build thread. Not planning on much other then relocating the pmd and possibly exhaust and the changing the waste gate over. It will get the 265's off my current one as well as some nbs wheels as soon as i find 2 more and some center caps.
 

Big Bertha

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Looks like the people here already addressed all of the issues I know of. Having recently bought a Suburban with the 6.5, I plan to do all the bolt on upgrades/correcting factory flaws, ie. PMD relocation, upgraded lift pump, manual WG, exhaust, cooling upgrades, etc. And run it as long as it goes, if it breaks then I'll go on the search for a 6500 optimizer, this is what I would recommend doing, they seem to be generally pretty reliable for the most part, FWIW the burb I just bought has 245k on it so far. Being that I wanted a Suburban, it was the 6.5 or nothing really. I certainly wouldn't buy a 6.2, and can't justify the expense of a dmax swap atm, although eventually that may happen. I wish GM would put the dmax in the Suburban, but us lowly peasants aren't worthy I guess. (The government can buy them that way)
 

JCribb

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Just reading the information on this thread itself is a refresher course for me as it’s been years since I wrenched on a humvee. I knew about the PMD and lift pump, but didn’t know about the dmax fan blade. I knew that the humvee’s cooling system sucked, but wasn’t aware that this platform was plagued as well.
 
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