I have a chance to acquire a very high end diesel powered air compressor Atlas Copco XAS-350. It is the kind of compressor that is big enough so that you cannot tow it behind a pickup. The compressor has a "blown diesel engine". I saw it in person and the engine is all covered in black oil, but does not seem to have any externally visible damage.
I will make an offer low enough to make money from just the air end and engine parts, like the injection pump etc. But I have a question. What exactly happens to diesel engines that make them blown? Head gasket? Or damaged pistons and rods?
"Blown" in this context does not refer to damage. It refers to having a supercharger - a "blower" - that increases the amount of fuel/air mixture going into the engine, making it more powerful.
Or at least one hopes so -- given the importance of getting it right, you might want to ask.
I the US, a "zero hours" airplane means one that hasn't been flown any significant amount after it's last major overhaul, and is therefore legally "as good as new". In Europe, a "zero hours" airplane is one whose time has run out before that major overhaul.
Imagine the surprise of the US customer who buys one without double- checking on terminology.
For sure I was informed that the engine is damaged. It was described as blown engine. I bought another compressor there that works great, I already ran it.
I was honestly told that one works great and the other has a "blown engine".
Well, then it sounds as if it's just an engine that doesn't work. Engines might fail for any number of reasons. A blown head gasket is relatively easy to fix. A broken connecting rod that has gone through the cylinder wall in the engine block means the block is ruined beyond repair.
That's an older 2 stroke diesel. Popular and well regarded, noisy and not the most fuel efficient. Anything could be wrong with it and I'm guessing that if you wanted to put the compressor back in working condition then the best repair route for someone like you would be to swap in a good used 6-71 which you should have no trouble finding.
Same things as happen to gasoline engines--head gaskets, crank bearings, whatever...
Of course they're repairable up to a point at which it's either impossible if the block has been damaged irretrievably or parts are more than a used one is worth...
A quick google found in your area--
Listing ID 62113 Country United States State (USA) IL Make Detroit Model Number 6-71 (238 HP) Serial Number Cylinders 6 V or Inline Inline ... Application Industrial Last Used in ? Condition Runner Weight (Kg) Cooling Method Water Dimensions Price Lead Time In Stock
Of course while the blower may be used on a 4 stroke to supercharge the engine in 2 stroke use it is often referred to as a scavenge blower and is there solely to blow fresh air into the cylinder to clean out any leftover combustion products.
All 2 stroke detroits are "blown" and the designation "6-71" means 6 cyls of 71 cubic inches displacement each - which is a 426 cu in motor. A 3-71 was a 3 cyl 213 cu inch engine.A 4-71 was 284, and I believe there was also an 8-71 monster 8-52 cu inch lump as well.
Since you say it is covered in old oil it could possible be a front oil seal and then the fan has blown the oil everywhere.
Years ago I came across a Hot bitumen tanker way out in central Australia and this is what happened to him. When I got there he was about to test it, having washed the engine down so as to see where the oil was coming from. I asked him how he washed it in the desert. His answer, "This is a bitumen tanker, without kerosene you are dead." :-Z At the next town we called his boss to arrange a 900 mile tow.
All Detroits of that ilk have blowers. It sounds like that's not the meaning here.
The damage could be fixable: blown seal, blown head gasket, etc. or $$$$: rod thrown through wall of the block, etc. No way to tell without a teardown.
I'm surprised there were straight 871's, I know of 8V71's.
The answer is Yes, assuming that parts are still available and while I can't comment on the U.S. I can say that parts are available in S.E.A. so likely also in the U.S.
Having said that I must say that of all the various diesel engines I've worked on Detroit Diesels can be the most frustrating as the basic (in your case straight 6) block can be fitted out with a host of parts. Right or Left hand starters, a vast number of injectors, various alternators, crankshafts, flywheels, water pumps, governors, and just about every part can be changed to another configuration. The engine as sold included a data plate on the top of the valve cover listing all the various parts and their part number but usually in old engines that plate is missing.
Black stuff all over the engine is oil and where that oil came from probably is the critical point. But (again) of all the diesels I've worked on Detroit's have probably the worst record of running away and a run away diesel usually stops because of some catastrophic failure, so a "blown Detroit Diesel" probably needs a pretty good look before buying.
Finally, Detroit diesels were cheap in price, high in horsepower (for their size) and had lousy fuel economy. In today's world I'm sure that they would be considered polluters :-)
So do I, for one thing they are extremely flexible. If you don't like the governor, just change it to a different type :-). On the other hand they require periodic tune-ups which most diesels engines do not need. Adjusting the rack on a V-12 Jimmy is a learning experience in itself.
(Jimmy = GMC = General Motors = the makers of the Detroit Diesel)
I did have a DD 3-53 diesel once that went into a runaway mode right after having been started.
It was a harrowing experience, because it was with me inside an enclosed trailer.
Fortunately, I was warned about it and I had a wooden paddle to shut off air intake. Even with the paddle, it barely stopped. I almost needed to change my underwear.
The problem was that rack that was stuck due to having sat around for years without having been started.
If they ever made an 871 it might have been the lay-down version they use in Crown Coach school buses. Amidships, under the floor. The standard was the Detroit 671 or the Cummins NHH.
LA Unified Schools alone is still running thousands of 30 to 50 year old Crown buses that still pass their annual safety inspections - the old coaches were so over-built the 1950 and later met the 1977 upgraded rollover standards. No road salt here.
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