Blown multifuel motors

With the recent number of multifuels that have cut loose lately, I thought those who experianced a grenaded engine could post when and the extent and the theory of what might have been the culprit. So if you could list the type/manufacturer of motor.
What aparently blew.
The date (aprox).
How you were driving ie. what RPM's and Speed.
And any comment you'd like as to why you think it went south.
There seems to be a common denominator here that is comeing to light....and that is the number six rod blowing. The last to recieve oil may have everything to do with it.... We all know the two best solutions to oiling is to get the Spin-on oil filters, currently the easiest to come by, JTonka's. They are anti-drain back thus leading to a quicker lube time, and ofcourse if we incorperate a pre-luber, we have effectivly addressed all of the shortcomings of the oiling on the multifuel.
The other thing that seems to be apparent in blow's is maxing RPM's for extended lengths of time, or esentially the same thing, trying to run at 60+ mph. I'm gathering that some of us, some of the time, DO run this way. And also that there is probably a larger number of us that do not.

there is an entire topic that covers this with info from the military and all the possible reasons why. you'd be very surprised at the information contained in that topic.

jwaller said:

there is an entire topic that covers this with info from the military and all the possible reasons why. you'd be very surprised at the information contained in that topic.

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Yes, but much of the surprising information had to do with the military users of the engine. We, presumably, are more gentle on our engines, and don't do things like stuff gasoline soaked rags into the air bell, and then run at full throttle.

-Chuck

stumps said:

We, presumably, are more gentle on our engines

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maybe so but you never know.



http://www.steelsoldiers.com/deuce/28192-multifuel-engine-life-facts-uncle-sam.html

for those that haven't seen it.

GoHot229 said:

With the recent number of multifuels that have cut loose lately, I thought those who experianced a grenaded engine could post when and the extent and the theory of what might have been the culprit. So if you could list the type/manufacturer of motor.
What aparently blew.
The date (aprox).
How you were driving ie. what RPM's and Speed.
And any comment you'd like as to why you think it went south.

Click to expand...

A couple of additional questions I would like answered:

1) Was the engine remanufactured? If so, who did it?
2) Which cylinder threw the rod? (#1 front, #6 against firewall)
3) Was the crankshaft journal burned and scored, or still shiny?
4) Was the rod cap still attached, or were the bolts sheared free?

-Chuck

Going to get a Christmas tree and running in the NAM are related how?

NO oil pressure on start and non for too long after!? is WHY Ive fitted pre-lube pumps on all my trucks! well at least I feel that more reasured/happy with (at least) 15lbs pressure BEFORE I hit the go button.

dmetalmiki said:

NO oil pressure on start and non for too long after!? is WHY Ive fitted pre-lube pumps on all my trucks! well at least I feel that more reasured/happy with (at least) 15lbs pressure BEFORE I hit the go button.

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That helps prevent dry bearing wear on start up, but I don't think it has anything to do with the rod failures that are vexing us. None of them look like seized bearings; all that I have seen (so far) look like over speed failures.

-Chuck

Earth said:

Going to get a Christmas tree and running in the NAM are related how?

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The only similarity it requires, I believe, is long periods of high RPM operation of the engine.

A deuce with standard tires, tooling down the road at 55MPH, is rather a kin to running a passenger car at the redline continuously. It works for a while, but in the end it will shorten the engine life.

-Chuck

Chuck you aren't speaking from memories are you ????????

Scarecrow1 said:

Chuck you aren't speaking from memories are you ????????

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I'm way to conservative to ever be a racer, but I have a number of friends that get their kicks pushing the iron past its safe limits. It works for a while, but in the end it results in a 2 or 300 hour engine life... sometimes much less.

I have never seen anything detailing the design parameters for military engines, but I have no trouble at all imagining the designers allowing the operator to push the hardware well beyond the safe limits... All I have to do is recall the WEP position on the old piston engined aircraft throttles. Use it once, and a rebuild is in order.

-Chuck

I have one here that vented the block with #6 rod.

and i have laid eyes on 10 or so more that tossed the same rod.

2 of these also had a bad turbo and dumped most of the engine oil out the stack.

I more or less was interested in a count of blown motors over this year, it seems two motors just blew in as many days here on the forum posts......and a couple last month. But if modified motors blew at significantly larger or smaller number some correlation might be arrived at, who knows.....

Does high compression play a factor here? Seems to me the multi's have really high compression, and that would incur more stress on the rods. At high speeds it may just be too much. I think I'll slow mine down.

#6 is the last to get oil pressure on startup, so it's logical that it is where the most problems would come from.
When my engine had it's little 'adventure', it was running about 2400 rpm's. So I've been running the one I took to the GA rally between 2200-2300, usually on the low side. That one only drops down to 2100 pulling the MKT on all the local area interstate hills. I don't mine going 48-50 MPH if I don't have to replace engines - just takes a bit more planning to arrive on time.

Earth said:

Going to get a Christmas tree and running in the NAM are related how?

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Hey Man, my daughters were getting antsy. . .

SCSG-G4 said:

#6 is the last to get oil pressure on startup, so it's logical that it is where the most problems would come from.
When my engine had it's little 'adventure', it was running about 2400 rpm's. So I've been running the one I took to the GA rally between 2200-2300, usually on the low side. That one only drops down to 2100 pulling the MKT on all the local area interstate hills. I don't mine going 48-50 MPH if I don't have to replace engines - just takes a bit more planning to arrive on time.

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Did yours throw #6 too?

A few more #6's, and we might be justified in declaring a trend. Perhaps this is why they upped the flow on the oil pump in the LDS engines?

-Chuck

GoHot229 said:

I more or less was interested in a count of blown motors over this year, it seems two motors just blew in as many days here on the forum posts......and a couple last month. But if modified motors blew at significantly larger or smaller number some correlation might be arrived at, who knows.....

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By "modified" do you mean rebuilt? I was curious to see whether the factory built engines fared better than the Toole rebuilds.

-Chuck

How much if anything (longevity) would be gained by balancing the rotating assembly?

If you look at other diesel engines of similar size and vintage of the multifuel you will find that most of them list max RPM at around 2100. IMO running at 2400+ is just too much.

One more thing to consider is that there is no telling how hard your truck has been run while in the military. More than likely all of our trucks have been ran at redline and beyond while they were in service.

Another thing that would be interesting to know is what unit the trucks in question came from. I have found out that my truck came from a maintenance unit of the TN/NG. The truck never left the NG base and was only used to haul maintenance items on base. I tend to think it had a much easier life than most other trucks.