Piston Rings Worn Out, Time for a Rebuild

Jeepsinker · May 4, 2015

At least hone the cylinders lightly. There are no valve seals, just guides. Someone here has installed some valve seals before on these engines but I don't know the details. The guides are iron.

Wildchild467 · May 4, 2015

Jeepsinker said:
At least hone the cylinders lightly. There are no valve seals, just guides. Someone here has installed some valve seals before on these engines but I don't know the details. The guides are iron.

Thank you for the information. So I would think the guides are still in good shape then, right? I would think with the little hours these engines have on them, I doubt anybody ever wore them out. A valve lapping couldn't hurt either.

gimpyrobb · May 4, 2015

Ted and I have been looking over some deuce heads. He mentioned that one set of heads had progressive springs(thicker at the bottom than the top) compared to another head from an LDS427. Might want to check that too.

Wildchild467 · May 11, 2015

I will. I will check for cracks on the pistons and the heads while I am there. There was also two different compression ratio pistons from what I have researched. I believe there was a 20:1 piston which was replaced by the 22:1 compression piston. I will have to double check mine to make sure they are the correct ones, which I would think they are. The blowby only seems to be puffing out the breather tube, so it might be a bad ring in one cylinder and worn out ones in the other cylinders. I would love new pistons and liners, but those are pricy. It if will run great with just rings and a hone, I will go that route.

Wildchild467 · May 18, 2015

I think i really need rings now. I came back from the Findlay Ohio Show and it just does not seem to be running that well. Decent amount of blow by coming out of the slobber tube in a series of puffs, similiar how it would be if one cylinder is not sealing properly (rings, cracked piston, whatever it may be). So I am in the market for piston kits (pistons and sleeves), rings, maybe main bearings (just because I will be in there and might as well replace them if they look warn even though i have good oil pressure), cylinder head gaskets, maybe connecting rod bolts as well just to be safe. I dont have the time to take it apart right now unfortunately and it may be a month or so by the time I get around to doing it. It makes me sad. So if anybody has any of these parts, let me know. When I tear into the engine I will document my findings in this thread.

If anybody has any suggestions of what I should look for while I have the engine apart, please let me know. Things such as common places a head might crack that I could look for (if they have a common spot they crack at all), check for worn valve guides since I have the head off, etc. Lots of you may have found something when you had your engine apart and it would be good to pass on the knowledge. Thank you all.

Hainebd · May 18, 2015

Sorry she needs a rebuild. Are you having or are doing the heads when you have apart? If so what are you doing?

HanksDeuce · May 18, 2015

Would a replacement engine be any cheaper? I sold mine for $800 with the 5 speed behind it. (For reference. Don't not know rebuild part costs.)

cattlerepairman · May 18, 2015

HanksDeuce said:
Would a replacement engine be any cheaper? I sold mine for $800 with the 5 speed behind it. (For reference. Don't not know rebuild part costs.)

Trying to avoid a flamed discussion here. It is a little bit like having cheap carpet installed...the labour is exactly the same. It depends what one wants. If the goal is just to have a running truck, a good takeout is probably the most cost-effective way.

One needs to compare apples to apples. How much is a REBUILT engine in a crate (they are still out there). Probably around 2-3k. That is the benchmark to compare the planned rebuild to.
Yes, a takeout is cheaper, but it is also the great unknown and has a certain likelihood to be inferior to a semi-rebuilt engine that hat its innards at least measured and checked and whatever needed to be replaced, replaced.

Wildchild467 · May 27, 2015

Well I did a compression test on the engine last night and got the following numbers:

#1 - 390 PSI
#2 - 290 PSI
#3 - 380 PSI
#4 - 320 PSI
#5 - 380 PSI
#6 - 360 PSI

I think #2 cylinder took a #2 (little joke there) because when I look at the blowby coming out of my slobber tube, you can see it is almost like a fast puffing smoke which made me think that only one cylinder went bad. Its a messy job pop testing, a little oil still came out of the injector lines and the air really shoots out of the injector holes when you crank the engine over.

So I am looking at a engine tear down in a couple weeks. I am wondering what route to go and how to get there. I want to put new piston kits in and all new bearings just to make sure. The engine does not have any ID tags indicating a rebuild which would indicate if the crank was turned or not so I think I will get all standard bearings. The oil pressure at the moment is 30psi at idle and about 60 at 2000 RPM. It seems like it has been a little lower lately but that is only using the electric gauge on the dash, not a mechanical one. It could be variation there, but I doubt it. it has always been reliable. My theory is that the blow by is diluting the oil a little.

DavidWymore · May 27, 2015

I strongly suggest you adjust the valves before tearing into it if you haven't recently.

http://www.steelsoldiers.com/showthread.php?28198-Multifuel-valve-adjustment-TM

Csm Davis · May 27, 2015

Wildchild I would treat it like a race car engine if you plan on keeping it for the long haul. Have good shop check everything for cracks and blueprint the engine and a balance job, it might sound like a waste of money to some to do this to a slow old multifuel but I think it would take the worry about slung rods away. I would see about anything else the shop could do to help keep your rods in one piece, maybe cryogenic and peening.

Wildchild467 · May 27, 2015

Hainebd said:
Sorry she needs a rebuild. Are you having or are doing the heads when you have apart? If so what are you doing?

I'll check the valve seats and guides to see how they look. If the guides are worn, I might get new guides and valves. I think seats are still available too. If everything feels tight, I will probably just lap the valves.

I should do a leak down test before I pull it apart too so I can see where the leaks are besides the rings.

Wildchild467 · May 27, 2015

DavidWymore said:
I strongly suggest you adjust the valves before tearing into it if you haven't recently.

http://www.steelsoldiers.com/showthread.php?28198-Multifuel-valve-adjustment-TM

I like your thinking. I did check the valves before I did the compression test. They were all within spec. Adjusting valves is inexpensive and the best bang for the buck to help keep an engine running strong.

Wildchild467 · May 27, 2015

Csm Davis said:
Wildchild I would treat it like a race car engine if you plan on keeping it for the long haul. Have good shop check everything for cracks and blueprint the engine and a balance job, it might sound like a waste of money to some to do this to a slow old multifuel but I think it would take the worry about slung rods away. I would see about anything else the shop could do to help keep your rods in one piece, maybe cryogenic and peening.

That would be great, but its just going to be an in frame rebuild and i dont really have the time and money to put into it for all of that. I agree it helps any engine. That is one of the reasons I just limit the engine to 2300 RPM redline... no reason to push it harder. I also keep my engine oil at the full mark at all times. I never let it get low at all. I think starving for oil or letting it get low can not help the engine out at all. It has ran good for over 35,000 miles, so I think it seems to hold together ok.... just needs a freshen up.

New rod bolts are about $16 each and I thought about putting new ones in.

Csm Davis · May 27, 2015

Definitely put in new rod bolts and I would check with ARP to see if they have one to fit.

74M35A2 · May 27, 2015

The engine is 40 years old. You are lucky the rings have any tension left in them at all. It is not so much a matter of 1500 hours, or even your 50,000 miles on the odo, as much as the repetitive heat/cool cycles over time. They may not really be "worn out" (end gap), but the tension against the cylinder wall is likely a fraction of what it was new. Come on guys, be reasonable, how long do you expect a medium duty engine to run/last without rebuild? And as others have said, especially with the lower quality of materials of that time, vs todays. You are also running non-approved fuel (WMO), which is totally knarly, but then expect the unexpected. Likely a non-issue here though.

In lieu of that, try to upgrade the materials if possible. It could even surprisingly be less cost than NOS. Start by calling piston/ring/bearing makers, telling them what you have, and ask if they have updated materials which would fit your engine. Things in stock at military surplus distributors are likely to be NOS, which would get you back to near new, but with the same decades old technology.

As comparison, the Kubota engine in my diesel light tower has a 22:1 compression ratio, and the Kubota manual states cranking compression pressure testing should generate 412psi-469psi. Cranking (dynamic) compression is greatly affecting by valve timing events (cam profile), so it is not directly apples-to-apples, but just a rough reference.

rustystud · May 28, 2015

74M35A2 said:
The engine is 40 years old. You are lucky the rings have any tension left in them at all. It is not so much a matter of 1500 hours, or even your 50,000 miles on the odo, as much as the repetitive heat/cool cycles over time. They may not really be "worn out" (end gap), but the tension against the cylinder wall is likely a fraction of what it was new. Come on guys, be reasonable, how long do you expect a medium duty engine to run/last without rebuild? And as others have said, especially with the lower quality of materials of that time, vs todays. You are also running non-approved fuel (WMO), which is totally knarly, but then expect the unexpected. Likely a non-issue here though.

In lieu of that, try to upgrade the materials if possible. It could even surprisingly be less cost than NOS. Start by calling piston/ring/bearing makers, telling them what you have, and ask if they have updated materials which would fit your engine. Things in stock at military surplus distributors are likely to be NOS, which would get you back to near new, but with the same decades old technology.

As comparison, the Kubota engine in my diesel light tower has a 22:1 compression ratio, and the Kubota manual states cranking compression pressure testing should generate 412psi-469psi. Cranking (dynamic) compression is greatly affecting by valve timing events (cam profile), so it is not directly apples-to-apples, but just a rough reference.

Totally agree with you on this ! People would be surprised at what can be retrofitted into older engines with just a little help. I'm sure there is a ring manufacturer out there that can come up with rings to fit our Hercules engines. As far as the rod bolts go, there is already a good replacement out there. You can buy the 12 point rod bolts from "Maibach" tractor supply.

Wildchild467 · May 28, 2015

74M35A2 said:
The engine is 40 years old. You are lucky the rings have any tension left in them at all. It is not so much a matter of 1500 hours, or even your 50,000 miles on the odo, as much as the repetitive heat/cool cycles over time. They may not really be "worn out" (end gap), but the tension against the cylinder wall is likely a fraction of what it was new. Come on guys, be reasonable, how long do you expect a medium duty engine to run/last without rebuild? And as others have said, especially with the lower quality of materials of that time, vs todays. You are also running non-approved fuel (WMO), which is totally knarly, but then expect the unexpected. Likely a non-issue here though.

In lieu of that, try to upgrade the materials if possible. It could even surprisingly be less cost than NOS. Start by calling piston/ring/bearing makers, telling them what you have, and ask if they have updated materials which would fit your engine. Things in stock at military surplus distributors are likely to be NOS, which would get you back to near new, but with the same decades old technology.

As comparison, the Kubota engine in my diesel light tower has a 22:1 compression ratio, and the Kubota manual states cranking compression pressure testing should generate 412psi-469psi. Cranking (dynamic) compression is greatly affecting by valve timing events (cam profile), so it is not directly apples-to-apples, but just a rough reference.

Very good thoughts there. I agree no doubt. Bearings are no problem... not sure if the piston rings are the same as the White 2-135 Tractor engine though. If they were, I would be all set! It depends on the dates that are on the rings too maybe if i got NOS ones.... you think? I believe they kept rebuilding these engines up into the late 90s so I doubt they are NOS piston rings from 1969. I totally agree with what you are saying though.

Jeepsinker · May 28, 2015

Even new old stock rings from 1969 would work fine. The rings don't go bad sitting on a shelf, they lose their spring by being compressed in a cylinder for a long time.

Wildchild467 · May 28, 2015

Jeepsinker said:
Even new old stock rings from 1969 would work fine. The rings don't go bad sitting on a shelf, they lose their spring by being compressed in a cylinder for a long time.

I guess overheating does not do them any favors either.

Piston Rings Worn Out, Time for a Rebuild

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