6.2 or 6.5 - What's really better?

Edis06

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Ok, it's confirmed that I have the 6.2 in my 1994 Humvee. I understand the campaign that existed to upgrade the in-service 6.2s to 6.5s and 1994 was the last year to require it. Mine was never done.

From what I understand there is a small increase in HP and torque and it is a "smoother" engine.

Are these the only advantages?

I ask only because I have access to a cleaner, lower mileage 6.5 for only $475. It was removed to install a duramax. Has all the pumps, generator, etc., attached. Looks very clean.

Is it entirely difficult to do the swap? The Army training manuals say it's a direct swap. Anyone have practical experience with this?
 

Coug

Well-known member
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The 6.5 GM is definitely better, it took care of a few issues with the 6.2, but also has some of it's own.
The 6.5 GEP is better than the 6.5 GM, took care of some metallurgy and heat soak issues still found in the GM block.

Look at it this way, if the 6.2 was better, then why did they stop using it?

If nothing else, for that price buy the 6.5 and stuff it in the back of the garage until you need it. If you currently have the 3 speed, start gathering everything to do a 4 speed conversion, then when you are ready just pull the 6.2 and 3 speed out, and put the 6.5 and 4 speed in.

That's what I would do if I was in your situation.
 

98G

Former SSG
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6.2 to GM 6.5 is probably not worth the effort. You'd probably never notice a difference.

6.2 to GEP 6.5 is an upgrade, but why bother if your 6.2 is running ok?


But at that price, grab it and have it on hand in case your 6.2 takes a dump some day.
 

Retiredwarhorses

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I have 6.2’s that beat the pants off of many 6.5 GEP’s. If it’s detuned, the 6.5 of any mfg makes it mimic the 6.2, thats why they labeled it “detuned”. If you want a super smooth motor, install a late Maximizer GEP 6.5 with larger IJ pump and injectors, you will need to do some throttle shaft mods to get the fan cutoff to work As the late style used a throttle position sensor.
 
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Edis06

Member
35
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8
Location
Florida
I'll know tuesday or so, whether or not I buy it. I notified someone on the forum that I'll let them know if I don't as he wants it.

I'm happy with my engine, however it's not in the "prettiest" condition. I'm nearly done doing a light resto on the truck and it pretty much looks new now and I'd love to have a shiny engine to go with it. The used 6.5 isn't like new - but it appears cleaner than mine.

Also, this is my first humvee, so I'm not exactly sure how well mine runs since I have nothing to compare it to, really. It fires up IMMEDIATELY, half a crank, regardless of temp. It vibrates something terrible, but that's comparing it to a car, not another humvee. It seems sluggish, like very slow, but I've taken it off road and I can't get it stuck. I've tried lol. Right when I think it's giving up, it slowly climbs out. The truck will do 60 with ease and it's not bad on gas. It actually gets the same mileage as my i5 H3. There is ZERO blowby and while it appears to smoke a bit of blue, it doesn't seem to burn oil to a noticeable amount on the stick.

My only concern was the chirp/squeak I get about half the time I drive it. When looking for the origin of the noise, I noticed the crank pulley seems to be vibrating a bit. I looked and couldn't find any deterioration of the rubber, as I've seen on others removed online. I don't know much about diesels so I'm not sure if this is normal. BTW, when I say "vibrate," I'm talking barely. Obviously, if it were severe, those V belts would be toast.

Just to be sure, I ordered all new belts, a new crank pulley, dampener and front seal. I might order a new water pump and fan clutch also, just to replace it now so it doesn't fail on me later.
 
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