O.T. Chevy diesel experts [6.2]

I was looking through my service manuals at home and found that GM used 2 - 6.2 diesels in their 1986 trucks..... The RPO [ regular production option ] in the book says there is a LH6 diesel and a LL4 heavy duty diesel...Mine is a "J" code which makes it an LL4 H.D......The other is a "C" code marked diesel.....What's the difference in the 2 engines ???? Thanks , Roy

Th LH6 was used in half ton pickups and the pollution controls made them basically junk on wheels.they came out in the 82 pickups

I think the main difference is the "J" code engine would go about 10,000 more miles before it broke the crankshaft! :-(

Emissions controls and that is it.

There are actually three versions. 6.2 C-code, 6.2 J-code, and 6.2 J-code commercial/military

C-code engine uses its own emmissions package, a heat-riser on the driver's side exhaust manifold, a special intake manifold with an EGR valve, the smallest precombustion chambers in the heads, and a detuned fuel injection pump.

J-code as found in 3/4 and 1 ton civilian trucks, vans, Suburbans, etc. Few emission devices, wide-open intake manifold, next step larger precombustion chambers in the heads, smaller valves in some HD models, and an injection pump with a higher delivery rate and a different part # delivery valve.

J-code commercial/military basically the same as civilian except for a few tweaks in the fuel injection pump and even larger precombustion chambers in the heads. Also, so have thin-fuel kits in the fuel injection pumps.

All the engines up to 1991 use the same blocks and cranks. When the 6.5 first came out, it used the same block as the 6.2, and both versions uses a new-type crank with a one-piece rear-main seal.

GM had Detroit Diesel design the original 6.2s to be equivalent in power to the 305 gas engines. They do that job just fine.

I've got 235,000 miles on my "junk" C-code 6.2. It's an 86 K5 Blazer with a pop-up roofed motorhome body on it. Weighs 7000 lbs. when it's loaded with gear and has a few people in it. Besides camping and travelling every summer with it, I plow snow with it in the winter.
3.08 axles, 700R4 trans, 4WD, and it's been great. Never had a major engine problem.

I also have an 82 K10 4WD truck with 6.2 diesel. 3.08 axles and a four speed overdrive manual trans. It too has been a great truck and plows snow every winter. Has 120K miles on it.

And, also have an 83 K5 diesel plow truck. All it does is plow snow in the winter. Yanked the 700R4 years ago and stuck in a TH400. Has 180K and never had a major engine problem.

One photo of my diesel mini-motorhome is before I did some body work, and one is after.

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