Piston Rings Worn Out, Time for a Rebuild

[Wildchild467]

Well, I think I have been trying to fight off he realization that I need new piston rings in my M35A2. I have some blow by and it never liked starting when it was cold out. I had the cylinder heads off once before just to put new gaskets on and there was hardly any ridge on the cylinders. The engine has about 1500 hours on it. I think all I really need to change the rings are cylinder head gaskets, oil pan gaskets and piston rings. Is there something else I might be missing or things I should look for when I change the rings? The engine had good oil pressure so I planned on using all the same bearings but maybe replacing the rod bolts if there was a newer or improved bolt out there for this. Any advise would be helpful. I am just not looking forward to tearing the engine apart in the truck to put new rings in it. Its going to be a messy job and I hope I dont pull it apart and realize I need a part and have to wait until it arrives. It would be great if I could have it done in a day. Thank you all.

 

[dmetalmiki]

OK, but what engine / truck are we talking about? at least give us (all) a clue.

 

[Jeepsinker]

Multifuel deuce.

 

[Jeepsinker]

I would try and find a set of rings for one cylinder, buy them, then try and match them up to a better quality new production set. Something that will last longer. Rings that only last 1500 hours almost have to be made of crap material, unless you consider the whole multifuel dry start issue. Maybe use nos rings and install spin on oil filters. Give that a try?

And you should at least replace the rod bearings and rod bolts. You can reuse them but it isn't a good idea.

 

[jpg]

I found this interesting. He installs gapless rings, dramatically reducing blow-by and keeping the oil much cleaner. I'd consider this if I were installing new rings. The video is a 6.5, but I imagine they come in deuce size.
https://www.youtube.com/watch?v=f3z6DotB7S8

Edit: Sorry. That was the wrong video link. Fixed.

 

[gimpyrobb]

So you got me interested, H.T.F. do you install gapless rings!?

 

[Jeepsinker]

Same way you install a one piece gas ring on an AR-15 bolt. You kind of thread it on like a heli coil.

 

[welldigger]

How does a gap less ring account for heat expansion? That's what the ring gap is for in the first place. It should close up when the engine gets to operating temperature.

 

[welldigger]

I would try and find a set of rings for one cylinder, buy them, then try and match them up to a better quality new production set. Something that will last longer. Rings that only last 1500 hours almost have to be made of crap material, unless you consider the whole multifuel dry start issue. Maybe use nos rings and install spin on oil filters. Give that a try?

And you should at least replace the rod bearings and rod bolts. You can reuse them but it isn't a good idea.

The top ring does most of the sealing. The second ring down scrapes most of the oil away before it gets to the top ring. Not saying dry starts aren't a small factor but I doubt it's the reson. I have seen multifuels being run hard for hours a day running a drilling rig and after thousands of hours they have little blow by.

I honestly am coming to the conclusion the multifuel likes being slapped around a bit. Those are the engines that seem to have the fewest problems. Versus the ones that sit endlessly.

 

[jpg]

So you got me interested, H.T.F. do you install gapless rings!?

See corrected video in #5. Basically, you replace the old ring with 2 thinner rings, and put the 2 gaps on opposite sides of the piston. I've not done this. I just saw the video and found it interesting.

Here's a link to the right video. Sorry about the error.
https://www.youtube.com/watch?v=f3z6DotB7S8

 

[gimpyrobb]

That makes much more sense, thank you! I know I am not up on current motor tech, but no gap, I couldn't figure it out.

 

[welldigger]

Ah so there is still a gap in the ring....persay.

I have been reading and apparently not everyone is in love with gapless rings. It really seems to be a hit and miss affair.

 

[gimpyrobb]

I have been reading and apparently not everyone is in love with gapless rings. It really seems to be a hit and miss affair.

Like this?:
https://www.youtube.com/watch?v=IJkL0t-sZvs

 

[welldigger]

Like this?:
https://www.youtube.com/watch?v=IJkL0t-sZvs

Well... it's about as fast as a deuce.

 

[Wildchild467]

I am going to Findlay so if anybody has any related items that I may need when I change my piston rings, let me know. I would be looking to buy/borrow a quality cylinder head wrench as well.

 

[DieselBob]

Ah so there is still a gap in the ring....persay.

I have been reading and apparently not everyone is in love with gapless rings. It really seems to be a hit and miss affair.

One of the big problems with the original “Gapless” design of 30 years ago was some designs used an overlap end that under extended use or very high compression had a bad habit of shearing off which lead to a somewhat dubious reputation in the early days of the designs.

 

[TGP (IL)]

1500 hours and the rings are shot?
I would take a close look at the air intake system before I run it again with new rings.
Sounds like there's a leak some place and the engine was dusted,
or it was severely overheated at some point.
Tom

 

[Hainebd]

A ring failure at 1500 is most likely due to being overheated. A small coolant leak can cause this. The multi fuel engine will run low on coolant for quite some time. I know when the guy drove brute to my house, the rain was steaming off the hood. I found out it had a small leak and was 2 gallons low. The heat takes the temper out. When you get one out the rings will not spring out.

 

[Wildchild467]

It has been hot a couple times when I had the winter front cover on and forgot to open it, but that was only about 225 degrees or so. It is toasty but not to the point where I would think the rings would weaken. It makes sense though if it takes the temper out of the rings... possible! Do you think I need/should to hone the cylinders too or just put new rings in?

 

[Wildchild467]

While I have the heads off, I think I might lap the valves also. It couldn't hurt. I looked in the TM to see if there was any intake and exhaust seals... but it looks like there are not any? If the valve guides are worn, I might put new guides in the heads as well. Has anybody ever done that before?