The Who's Who of 6.2L: C vs. J

[dieselcrawler]

Hey all, I'm new to the diesel thing, and was wondering what the diffrence was in the 2 avalible 6.2L motors, the "C" and the "J". I was under the impression that the J was a heavy duty version, and the C was normal duty. What's the real diffrence, how can you tell them apart, and how do the diffrences affect how our trucks run? If the 8th dig of the VIN is the motor type, I have a "J" in my K-30 CUCV 1028, as one would expect for a heavy duty mil truck. Thanks for any input...
Greg

[britannic]

"C"=Light Duty and is the EGR engine
"J"=HD as you say and doesn't have EGR.

The "C" doesn't breathe as well as the "J", because of the smaller cylinder head pre-chambers, valves (I think they're a tad smaller, but someone will need to confirm that), restrictive intake manifold (EGR and the way the intake manifold is designed). The IP is also thrifty on fuel, which along with the pre-chambers gives great mileage (in excess of 20MPG ).

Some quick upgrades for the "C" engine:

1. Lose the EGR system
2. Install a hummer intake manifold from eBay
3. Install non-EGR intake manifold gaskets at the same time
4. Turn the IP up or get one for a "J" engine (but the fuel economy will drop in proportion to the power increase).

A serious upgrade would include a pair of 6.5LTD cylinder heads and turbo :D .

[Peter J. Bierman]

Yes, you are right, normally all millitairy trucks have J engines, so if you have the original engine in there it's a J.

Peter

[dieselcrawler]

Thanks for the replys... As far as I know, mine is orig, and is a "J" motor. I am wondering, 'cause I might be getting another truck, a '85 C-10 w/ 6.2L and a 700R4. But as far as I know, it will prob. be a "C" motor, as it is a truck with A/C, tilt, PW, PDL, etc. My guess is that it's light duty. I haven't see it yet, or heard it run, but can get it cheap. I just want it for the motor, trans, and power stuff, want to swap it to another truck I have. But if there's a diffrence in the block itself, heads, etc, I may not want it.
I may also have another line on a CUCV motor, a friend of mine is getting one, only wants it for the D60 frontend/drivetrain. He will pull the 6.2L, drop in a big block. I think he's dumb, but I'll snach up the motor he doesn't want for sure! Always pays to have spare parts!
Is the "C" 6.2L worth the time? Should I save my money, and just get the CUCV "J" motor? Are there significant diffrences in the block and/or heads?

[britannic]

If it's a real CUCV engine, then the block will have been toughened with extra nickel alloy and should be crack free.

[dieselcrawler]

So what you're tellin' me is that for a 6.2L, the CUCV version is the best of the best? I bet that they will hold up to the stress of a turbo better then, too? **wink wink** I hope to put a turbo on it some time... and it seems to me that a CUCV "J" motor is a good base to start from, even with some miles on it.
Greg

[Dieselboy]

That's why I chose a CUCV 6.2L as my engine to rebuild. 25,000 miles later (3000 of those are with the turbo), and no problems. And it's seen its fair share of hard work. :D

It's too bad you're so far out east. There's a pretty big off-road gathering around here in April. Usually, one or two 6.2L guys show up, and we wheel for a few days. It's fun having the low end power for the trail and never have to drive into town with the gassers to fill-up. ;)

[dieselcrawler]

It's too bad you're so far out east. There's a pretty big off-road gathering around here in April. Usually, one or two 6.2L guys show up, and we wheel for a few days. It's fun having the low end power for the trail and never have to drive into town with the gassers to fill-up. ;) [/QB]**chuckle** Yup, I like bein' the odd one with a diesel, no one else runs one, at least not REALLY wheelin'... some tow their trail rig w/one. Drop the ol' 'Crawer in low range, and hit the trails... I'm sold on a diesel powered trail rig now. Hope to put on a turbo by next spring/summer.
'Till next time,
Greg

[Peter J. Bierman]

I used the CUCV J engine for the TTD project,
no problems so far.

Peter

[dieselcrawler]

How about some input on this... a "J" motor, the one that is in my CUCV, with about 100,000 miles on it... I want to put a turbo on it, but don't know it this motor will last with the new found stress of the turbo. I don't want to do a compleat overhaul of the block right now, and hope to find another to build, and just change the long block at some point, in about a year or so. I don't want to get too out of hand, I'm not looking to make a 'race motor' out of it, just want a little more power, but want the most in relibility and longevity. And low price. Any thoughts on the kit sold by Banks? What kind of price range does this kit go for? Any one have a used one for sale? What parts can I salvage from other places, and if so, what are some things to look for, and look out for?
Thanks,
Greg

[Peter J. Bierman]

My CUCV Blazer had like 80000 on it by the time I started the TTD project.
Took it all appart but found no reason to overhaul the engine, Just the gaskets and the heads and it's running fine so far and I am convident to put on the marine DB2.
So I think you have a strong engine if its running OK and a good starter.

Peter

[Ratau]

How would one id a

[dieselhumvee]

dieselcrawler, where are you guys getting these Cuccv's? I wouldn't mind getting a cheap one to run hard off road.

[dieselcrawler]

Who ever said they were cheap? **grin** mine still isn't paid for! The former owner, who I still owe about half of the $2500 sale price, just shakes his head and rolls his eyes when he sees the ol' beast. Good thing he's a good friend! It was a nice, stock, straigt truck when I got it about a year ago.
As to finding a good CUCV, try this web site. www dot govliquidation dot com There in an artical in the latest issue of 4wheel and offroad magizine about just that, buying and wheelin' an old army truck, '86 CUCV, looks to be a M1008. Good luck...
Greg

[britannic]

When I replaced my worn timing chain with Dual Idler Gears and took the oil pan off to replace the rear seal, I was amazed at how new and unworn everything looked in my CUCV engine. Apart from the timing chain there wasn't any way to tell how many miles it had driven.

No cracks, machine marks still visible on the piston skirts and as far as I could see up the bores with a flashlight, the hone marks were still there - there's a lot to be said for the high nickel block :D !

[Bill]

The question still remains...can the motor be ID'd as a C or J from the casting, block number, or any other feature on a long block?

[cubby]

I've been trying to buy a CUCV from the Liquidation site for 1 1/2 years they sell for way to much money. Those guys are nuts. Also, most of them have the np208 scrap-fer case. I got lucky, I found one 2 weeks ago from a local guy, and bought it just for the motor and trans. I didn't have to pay $$$$.$$ for it either.
Sorry to be venting anger.I would also like to know if there is a way to I.D. C or J without taking the Oil pan off.

[Stage1]

A few questions on power modifications.

Is the HMMWV intake the same as the intake on a M1008...

What kind of torque increases are possible for non-turbo chnages such as:

Intake upgrade, IP modifications and/or upgrade, bigger injectors.

Did the military HMMWV's use the 6.5 engine and which head was used.

thanks,
Les

[Dieselboy]

Here's some intakes we happen to have on the shelf. http://www.handykult.de/plaudersmilies.de/happy/wink.gif

From left to right: '85 C intake, M998 intake, '93 6.5TD F intake.
http://www.oliverdiesel.com/inventory/differentintakessmall.jpg

Notice the air cleaner stud locations are different. Other than that, the C and J intakes have the same diameter openings and can use the same air cleaners and Banks plenums. The M1008 would have a J intake which is the same as the C version but without the EGR.

[ 02-27-2004, 09:14 PM: Message edited by: Dieselboy ]

[crew84]

I had to have two hole drilled into the Banks intake air chamber and plug the stock manifold mounting holes when I used the Hummer intake. I had a machine shop do it and it only cost $35.00. The Hummer intake is lower so the Banks tube from the turbo really uses the flexible hose from the turbo.

[Stage1]

David,
Thanks for the info and pictures, does the HMMWV intake flow more air vs the J intake? Not having looked at the intake ports and knowing nothing about diesel intake air flow dynamic, the J/C type intake looks fairly good.

How much testing has been done to compare the inakes for non-turbo applications?

thanks,
Les

[Dieselboy]

The ports on the intakes are all the same - 6.2 or 6.5L.

As long as you are using a J intake or an M998 intake, then you should be good. Both will flow a good amount of air. The real key is using a non-EGR intake.