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What does this engine tag mean?

Autonomy_Lost

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I'm not sure how to interpret this tag. Did my humvee get a new/rebuilt engine on the 71st day of 2002? My humvee is an 87, but this NSN number apoarently didnt exist until 1990. So it seems like it got a new engine at some point. And how do I interpret that date code? It says 02071.

Fwiw, the engine block says GM 6.2L D in the casting.

20210926_122321.jpg
 

Guyfang

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I'm not sure how to interpret this tag. Did my humvee get a new/rebuilt engine on the 71st day of 2002? My humvee is an 87, but this NSN number apoarently didnt exist until 1990. So it seems like it got a new engine at some point. And how do I interpret that date code? It says 02071.

Fwiw, the engine block says GM 6.2L D in the casting.

View attachment 846399
That plate tells me:
1. Engine replaced
2. Standard engine. No over size jugs or rings. Standard Rods and mains.
3. Repaired at MAK, (Maintenance Activity Kaiserslautern)

The date. Is a Julian Date. 02071 = 02. (the year 2002) 071= the 71st day of that year.

I spent a lot of time in K-town. And at the MAK. New engine? do not think so. The fine folks at MAK did rebuild these engines. Lots of them. More then stars in the sky. On the whole, they did a very good job.
 

gringeltaube

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2. Standard engine. No over size jugs or rings. Standard Rods and mains.
Now, someone please explain those other two non-std options....:?

Those numbers don't make any sense to me because:
1) In the real world there are only two oversize pistons available for these engines: +0.50mm and +0.75mm. (equivalent to 0.02" and 0.03", respectively). And AFAIK the military only ever used +0.50. Any block beyond that size went straight to the junk pile.

2) In order to achieve correct clearances, even a std size crankshaft normally takes std size bearings in combination with -0.013mm (= 0.0005" US) and -0.026mm (= 0.001" US). That goes for main bearings as well as rods.
But I have also found HMMWV engines with cranks ground to the next real undersize, which is -0.25mm (= 0.01" US). Besides that in the civilian world, bearings for these cranks are available in -0.50mm (= 0.02" US) and even -0.75mm (= 0.03" US).
 

Autonomy_Lost

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Location
Pennsylvania
That plate tells me:
1. Engine replaced
2. Standard engine. No over size jugs or rings. Standard Rods and mains.
3. Repaired at MAK, (Maintenance Activity Kaiserslautern)

The date. Is a Julian Date. 02071 = 02. (the year 2002) 071= the 71st day of that year.

I spent a lot of time in K-town. And at the MAK. New engine? do not think so. The fine folks at MAK did rebuild these engines. Lots of them. More then stars in the sky. On the whole, they did a very good job.
Wow, that's more info than I thought anyone would have! Thanks for the detailed and interesting response!
 

Guyfang

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Now, someone please explain those other two non-std options....:?

Those numbers don't make any sense to me because:
1) In the real world there are only two oversize pistons available for these engines: +0.50mm and +0.75mm. (equivalent to 0.02" and 0.03", respectively). And AFAIK the military only ever used +0.50. Any block beyond that size went straight to the junk pile.

2) In order to achieve correct clearances, even a std size crankshaft normally takes std size bearings in combination with -0.013mm (= 0.0005" US) and -0.026mm (= 0.001" US). That goes for main bearings as well as rods.
But I have also found HMMWV engines with cranks ground to the next real undersize, which is -0.25mm (= 0.01" US). Besides that in the civilian world, bearings for these cranks are available in -0.50mm (= 0.02" US) and even -0.75mm (= 0.03" US).
Well, I can't. I am a generator guy. The reason I know about the other stuff is because a Direct Support Shop Officer would get his head handed to him, if he didn't!

Also, while at R.O.B, Rhine Ordnance Barracks, K-Town Germany, stationed at the 549th DS Patriot Support Company, my shop was about 400 meters from the KAD German shop, responsable for rebuilding that engine. When you need an engine fast, its nice to know the boss there.
 

Mogman

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If it is a 6.2L then the actual year of the engine is insignificant, it was rebuilt in 2002
 

Mogman

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What does a rebuild usually entail?
I am not sure about military standards, in the civvy world a complete rebuild usually includes, new pistons, rings, all bearings including cam bearings, seals, gaskets, freeze plugs, the heads are given a valve job which may or may not include new valves, springs, guides and keepers, the cam is inspected or simply replaced. the heads and block mating surfaces are checked that they are true, the crank rod and main journals are inspected and re-ground as needed, the line bore of the mains and cam journals are checked, the heads crank and block are checked for cracks, the cylinder bores are honed or bored and honed, on a diesel the injection pump and injectors are replaced with new or rebuilt components, the oil and water pumps are replaced, the timing chains/belts are replaced and the timing gears/pulleys are inspected and or replaced the rods are inspected and or resized and upper bushings are replaced if the rods have them (some rods are press fit and do not have upper bushings) sometimes the rod, main and head screws are replaced (replacing the head screws is mandatory on the 6.2 and 6.5L as they are torque to yield, not sure about the rod and main screws)
And of course any specific known week points should be upgraded. And the engine is re-assembled.
 
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