C Code or J code

[48cj2a]

Besides the obvious with or without EGR how do you tell if you have a C or J code 6.2?

Are the block castings different?

Where are the date codes marked?

I have a 3/4 CC 2wd that has a GM Target replacment motor in it so would like to identify which engine I have and when it was produced.

[R/Cpullerdude]

The differences are accessorial. Basically EGR and related components and the pre-cups. Do you have an EPR valve in the exhaust or the EGR valve in the intake? IIRC, in the early years they may have had different size valves too, but I'm not positive on that.

[48cj2a]

The differences are accessorial. Basically EGR and related components and the pre-cups. Do you have an EPR valve in the exhaust or the EGR valve in the intake? IIRC, in the early years they may have had different size valves too, but I'm not positive on that.

So the only differences are the intakes, some plumbing and the smog stuff?

I just pulled the fenders off in the last couple nights and plan to pull the rad and core support tonight. Have not even pulled the lid on the air cleaner to check for EGR valve but the CDR is right behind the alt so makes me assume in could be an EGR type.

I'm replacing a blown J in my 85 CUCV and planned to transfer the intake and CDR over to this motor and any other recommended items.

[R/Cpullerdude]

So the only differences are the intakes, some plumbing and the smog stuff?

I just pulled the fenders off in the last couple nights and plan to pull the rad and core support tonight. Have not even pulled the lid on the air cleaner to check for EGR valve but the CDR is right behind the alt so makes me assume in could be an EGR type.

I'm replacing a blown J in my 85 CUCV and planned to transfer the intake and CDR over to this motor and any other recommended items.

There are also fueling differences. Easiest way to check is to just pull the air filter off and take a peek.

[48cj2a]

I understand if it has the EGR valve or not, but this is a Target replacement and not the original so anything could have been changed over during its swap if it came as a long block and not complete.

The parts guy could have ordered anything or if the dealership had one in stock they could have used what was available.

I wish to know how to ID the Target Block and know what I have.

[DmaxMaverick]

C or J is not determined by the long block. The ONLY difference, internally, is perhaps the precombustion chambers in the heads, specific to any production run. The later 6.5L had other differences, depending on application, but none of this applies to the 6.2L. It is very unlikely the configuration of the engine was changed by a dealer or other shop, simply because it is not legal to tamper with or modify emission systems from original. The consumer can do this (legal or not, depending on local/state law), but no shop can, legally. To replace a long block and not use the original accessories and manifolds would not be a common practice. Even if a take-out engine was used, the dealer or shop would have to either source an engine with the same emission equipment, or use the original equipment to ensure emission compliance. The C or J code is the 8th digit of the VIN number of the vehicle, and has no real bearing on the engine itself, other than how it is equipped. Within the same model year or production run, the long blocks will be the same (except for the pre-cups in many cases), and they would have the same casting number. There were only 5 applications of the 6.2L's: Pickup/SUV; Van; HMMWV/CUCV; Marine; and stationary. All of them started with the same long blocks. As far as the heads go, every production run used the same. There were valve size changes, but never during a production run for different applications. The valve changes happened during production run changes (model year increments) to accommodate emission updates and durability, but were not application specific.

If your engine has EGR/EPR with functioning vacuum and ECM systems, it is a C. If it has no EGR/EPR, it is a J, or modified C. Your 2500 CC should almost certainly be a J code emission standard, and the VIN should reflect that. If your GVWR is 8600, count on it. A GVWR of 7200 could have gone either way, depending on the state of original delivery.

[48cj2a]

Thank you for the education - that is exactly the info I wanted to know. Just was not sure if there were real differences in the blocks.

Where would the date codes be. Like I said this is a target replacment and would like to know what time frame it was produced.

Also back to the CUCV J engine. I have it disassembled and would like to know before I scap anything of value if there are particular areas of the head or block that would be obvious without spending money for magnafluxing and possibly have some spare parts or trading material.

Already thinking of getting the IP rebuilt and injectors checked then swapping later with this replacement motor.

Finally the replacement motor has at least one GP broken off so only the threaded portion remains. How do you remove one of these? Was thinking of welding a nut on it and see if it will back out.

[48cj2a]

Went out tonight after work and pulled the air cleaner - sure enough it is a J code (no EGR) and the VIN also confirms.

So what is the difference between a J code Civy and a J code Military CUCV?

[DmaxMaverick]

Went out tonight after work and pulled the air cleaner - sure enough it is a J code (no EGR) and the VIN also confirms.

So what is the difference between a J code Civy and a J code Military CUCV?

There's no difference with the long block. The only difference is what's bolted onto it.

[48cj2a]

Thanks DMAX,

I have the Mil 6.2 partially disassembled and would like to know before I scap anything of value if there are particular areas of the head or block that would be obviously seen without spending money for magnafluxing and possibly have some spare parts or trading material.

Already thinking of getting the IP rebuilt and injectors checked then swapping later with this replacement motor.

The Civy 6.2 has at least one GP broken off so only the threaded portion remains. How do you remove one of these? Was thinking of welding a nut on it and see if it will back out.

[DmaxMaverick]

Check the heads for cracks. Most often, a magnaflux isn't necessary, as critical cracks can be seen before. Look for cracks between the valves, and cracks in the pre-cup flash holes. Some cracks are benign. Cracks between the valves are normal, as long as they don't run into the valve seats, and the pre-cup cracks are normal and typical if they don't run into the fire ring (there will almost always be some cracks). The rest is just obvious. I've never had a magaflux reveal anything serious that couldn't be seen before. Adding a bit of heat with a propane torch (or mild heat with an oxy-acet) will cause impregnated oil/coolant to seep from cracks, easily revealing them.

Unless you have reason to believe the injectors are relatively new, don't waste the time/money to test them. Just rebuild/replace them. Refreshing them at a good shop is usually not expensive, compared to new/rebuilt, and a good tech will "balance" them for you (using all new same nozzles and ensuring the pop pressures are all about the same, which is no guarantee with new/rebuilt off-the-shelf injectors).

If you are able to weld on a nut, that would be ideal. The application of welding heat will often loosen the threads. Using candle wax can also be helpful, while the heat it still there. While it's still hot, let some wax wick into the threads, let it cool a bit (not so hot you can touch it for a second), and try threading it out. If it's still stuck, you can drill/tap the hole, or try a blow-out with a cutting torch. The glow plug metal is significantly softer than the cast iron head. It's pretty easy with the head off. Remove the pre-cup (be sure to reinstall it in the same orientation), which will allow for more room/visibility in the combustion chamber. Use a wood/composite/aluminum dowel to drive it out from the injector hole.

[Robyn]

Yesss the difference is the bolt on items.

The military IP is different (24 volt and fuel settings)

The heads (precups) IIRC are slightly different too.

Any 6.2/6.5 engine should be looked over in the center main web areas for cracks in the outer bolt holes that go down through the web.

These can be tough to see but careful checking will usually tell the story.

The heads can and do crack between the valves. In most cases, these cracks dont hurt anything but can go though to coolant.

Cracked precup ports are normal but, as long as the cracks dont cross the fire ring they are useable.

Any cracks in a head thats onto the "firedeck" is a death sentence.

Some 6.5 engines will crack the number 8 cylinder in the lower rear area about an inch down from the top.

6.2's generally wont crack cylinders.

Check the head bolt holes in the block for cracks that go either to the outside, the lifter case area or to a water jacket. These are rare but do happen.

Other than that, its just a normal inspection tour.

Missy

[twaddle]

Before getting the fuel injection pump rebuilt check the ID number for the build spec of the pump. Some of the Military 6.2s were fitted with artic spec components (hardened parts compared to standard) which allowed these engines to use all sorts of fuel (as in ''Multi fuel'' type use).

If your fuel pump is the artic spec I would leave it alone if all is well. It is unlikely that the injection shop will rebuild it to artic spec and if they did it would be way more expensive than the civvy standard spec.

When I lived in Scotland I had an ex US military M1008 pick up for about 10 years. My good Buddy Gord Ried at NW Fuel Injection in Surrey, BC warned me that to rebuild these artic spec would be costly. In the 10 years I used the truck as a service vehicle and ran it on kerosene, diesel and paraffin without any problems.

Good luck

Jim
Formerly Scotland now in the very frozen Northern Alberta.

[48cj2a]

Where would I find the spec listing to compare it to?


check the ID number for the build spec of the pump. Some of the Military 6.2s were fitted with artic spec components (hardened parts compared to standard) which allowed these engines to use all sorts of fuel (as in ''Multi fuel'' type use).

That would make sense with us using fuel like JP4 and JP8 today.



If your fuel pump is the artic spec I would leave it alone if all is well. It is unlikely that the injection shop will rebuild it to artic spec and if they did it would be way more expensive than the civvy standard spec.

This engine only had 4X,XXX miles so I'll check the spec and maybe go a head a swap it now and have my Civy one rebuilt as I do not even know any history of it or the milage factor.

[DmaxMaverick]

Ignore the odometer miles on military vehicles, for several reasons. Always assume they are at or near their service life, which can be quite subjective.

Keep in mind:
They idle 10 to 20 times more than any civilian vehicle. 40K miles on a military vehicle is a lot of engine run time. A whole lot!
They are often operated in climates and conditions not seen by civilian vehicles, for extended periods.
They are driven by a different person, every time, usually.
They are operated at their limits, almost all the time.
Throttles have 2 positions. On and Off.
While military maintenance requirements are about as good as it gets, most often, the maintenance cycles are forgone for extended periods when deployed. They get more periodic maintenance when they are not used (calendar maintenance). A vehicle may get 4 or more complete service intervals within 1,000 miles, then be operated for 20K+ miles with only minimal service, if any.

[Robyn]

I agree on the maintenance thing. Yeah buddy, can get the crap run out of them.

The stuff that is in good shape and been in a guard unit can be a nice find. They dont usually see loads of miles or time. Unfortunately these rigs come from the regulars as cast offs in many cases.

There is a local fellow here that has an Ex Mil Blazer and he runs that thing on a mixture of just about anything flamable.

#1
#2
Mixtures of old tranny oil and gasoline
Engine oil and gasoline
Hydraulic oil.
Vegetable oil
Jet A has been known to find its way into the tank.
kerosene

If he can find it cheap and it will burn, it goes into the Blazers tank. :eek:

Some of the stuff he burns smells terrible coming out the tail pipe :(

He has been doing this for many years.
He tried feeding his 7.3 stroke the same diet and it choked and puked on the stuff.

Whatever the Mil pumps are put together with seems to tollerate quite a broad range of burnable liquids.

I think he has even dumped in some turpentine once or twice.

I do remember him comment that the jet fuel made the little critter run really good, compared to some of the other concoctions that it had been fed.

Some mixtures are reported as HARD to lite off :rolleyes:

I dont doubt it.

Missy

[48cj2a]

The Civy 6.2 has at least one GP broken off so only the threaded portion remains. How do you remove one of these? Was thinking of welding a nut on it and see if it will back out.

Well I got around to working on the engine today. I have it on an engine stand so at least I'm not wrapped in a pretzel or bending over a fender.

The exhaust manifolds were pretty rusted and pitted and the original CUCV ones look better so decided I'd swap those and make working on this and a leaking FP Block Heater a little easier. CUCV one came off without incident but the bolts on the Civy are pretty rusty and made me pretty nervous taking them off. Ended up snapping a head of one of the manifold bolts and this took an hour or so beating on it with a hammer and twisting up and down to break it free from the remaining stud of the bolt.

Hit the broken GP with a wire wheel on the die grinder and ended up welding three different nuts on but they just were not penetrating the GP enough to stick.

Rotated the piston to TDC on the cylinder with the Broken GP...

Broke out my Snap on Extractor Set and my good Snap On Jobber bits.

Drilled bit by bit until reaching 1/4 inch and the extractor would just spin in the GP. Went ahead and drilled to 5/15 and it eventually chipped out most of the threads but would not extract. Began the process all over to 1/4" reaching the probe and it did finally back out but I must have drilled too far because the tip has pushed out of the GP. Worked on trying to grap it with a pick and lift it out for about 15 minutes and finally got it high and locked in place enough to grap with needle nose pliers all in one piece.

Adapted my shopvac down to a piece of 1/2" copper and sucked out the GP hole.

Swapped in a GP from my other heads. Now looking at the rest they are pretty rusty and tried to remove the next one but it feels like it could snap as well.

Is there any tricks to getting these out that are rusted in without breaking them off. I hate to have to drill everyone of these out but feel I should probably do this now while its on a stand rather then have to do it down the road later when its installed in the CUCV.

Also what is the thread tap size of these GP holes. The GP I installed did not thread in as easy as it came out of the other head so I'd like to chase the threads and make sure I did not bugger them with the drill bit.

[48cj2a]

Ended up finding the odd size Tap at Car Quest for under $8 with tax (Metric 10X1.0) chased the threads and made a workd of difference it threading in the GP.

Also purchased some CRC Freeze-Off Penetrant at O'Reilly's for $4.99.

Did break off the next GP but got the remaining 6 GPs broke free and chased the treads in the first broken one. Made a big difference after chasing the threads.

Went through the motions to extract the other broke GP and ended up snapping off my 1/4 extractor. Tryed several times to weld on a washer and nut and they all just twist free.

Tried drilling the broken extractor with Cobalt bits and does not seem like its ever scratching it.

Anyone have any other ideas, I really do not want to pull this head to take to a welder or machine shop to extract.

If I have 7 functioning GPs is the eighth one going to make that much difference?

[DmaxMaverick]

You won't miss one plug, unless you are in extreme cold (great north). It may give a puff or two of white smoke on a cold start, but nothing to worry about. I suggest you pull the injector, plug the flash hole (prevents any pieces from falling into the cylinder....don't forget to remove it when done) and break off / retrieve the plug tip. It may, at some point, decide to fall off on it's own, especially since you've been messing with the strength end. If possible, weld/braze/solder the outside to prevent compression leakage.

[48cj2a]

Any reason I can't fire this up with the civilian engine harness connected to the CUCV dash harness?

I would like to get this running and know its right before the adventure in swapping the dash harness.

Lastly what is the connection on the firewall power terminals that connects the Pos and Neg?