Cummins 5.9 UNEVEN ring end gaps

[DaveOmak]

Here's a theory... The top ring is the compression ring... If the second ring had less of a gap, it "might" or would become the compression ring... Maybe that's why they want more of a gap...

 

[fitterski]

Here's a theory... The top ring is the compression ring... If the second ring had less of a gap, it "might" or would become the compression ring... Maybe that's why they want more of a gap...

It's over my head, been a long time since when I was sittin' in class for basic engine theory! Yes, it's a compression ring too, catches maybe the 1/4 that got past the top ring but it's also an oil wiper, a finishing wiper like a windshield wiper. Explosion pressures in the head of the cannon get behind the ring to force it against the barrel wall (it's not the spring load that does this). So just maybe (here's MY theory) the finishing scraper function of this pointed sharp blade-edge ring doesn't really wanna be forced that hard against the barrel and to accomplish this a bigger gap gives some 'relief'. Now _I_ can get ready for my head up the u-know where scene :laughing:

Banned Super Bowl Commercial - YouTube

 

[DaveOmak]

Do the instructions recommend offsetting the ring gaps 180 deg. on the piston ?? Seems that would be the norm... with a back up compression ring installation..

 

[fitterski]

Do the instructions recommend offsetting the ring gaps 180 deg. on the piston ?? Seems that would be the norm... with a back up compression ring installation..

What they want done is staggering the gaps 120 degrees from adjacent ones. For a while I wondered how the rings would keep from turning, I guess they just don't. I opened this engine with about 120,000 miles on it and they were still staggered.

 

[fitterski]

Cummins Rocky Mountain in Gillette, Wy is open 24 hrs. 307-682-9611. The first question they ask will be the CPL number. Get your CPL number and call them. They have been very helpful to me. 24 hr parts is great too.

This link (so far alone out of a dozen including 3 emails to Cummins) bore fruit! KUDOS to Rocky Mountain Cummins!!!!

Whaaaaaada a mess, don't know where to begin. The engine number is 44966271 and the CPL is 1550. This was the engine number given to the API piston-kit supplier who sent me piston kit # 111336 inside which is ring-kit #505081 with OEM equivalent Cummins numbers of 3802494 & 3802232 respectively. No one (else) has been able to give me so much as diddly squat including PAI. The problem is that if I want to do a pro job I have to know the individual ring part number as per the Cummins QS web manual @

Cummins QuickServe Online | COLA

39190509

(red dots are the closest to paper manual values)

This page shows like 9 different gap ranges for each of that many ring part numbers for top as well as intermediate rings i.e. you don't go ANYWHERE without the ring part number. PAI however were unable to give me so much as the equivalent OEM numbers for the rings in *their* set, so much for PAI!

The hard copy manual that I paid $250 for states

Top 012-018
Mid 032-047
Oil 010-022

If I had gone with these numbers when my instinct first rang the alarm and I posted the originating article I 'might' have OVER gapped to the tune of 2 or 3 times spec which in my book means immediate execution by the shop door. I didn't, went looking instead.

So the gal at Rocky Mountain Cummins said "piece of cake, I can give you the cummins RING numbers that go into that equivalent cummins kit ...my, my, my ..how hard can THIS be everyone out there (not meaning this forum of course)??????

*her* part numbers and QS-based gaps

Top: 3919050 016-030
Intermediate: 3904347 010-024
Oil: 3904349

So after having lost confidence in the $250 paper manual, in PAI, in internet blog sources that do not quote precise sources, I wondered if my kit supplier got me the right set in the first place for my engine? I was so happy to hear the gal give me actual ring part numbers that I forgot to verify with her against the actual engine number. So I called back: the PAI kit number is the correct one for 20 over-bore, but it has been replaced by 3802422 which in turn looks like having a different oil-ring number 3933585.

(I spoke to both girls working there today BTW, I don't feel empowered to name them). I think they desrve the parts-dept nobel award!

I now have half a mind to chuck the entire PAI kit and order me a Cummins kit as maybe I should have done in the first place.

 

[DaveOmak]

Isn't that amazing...
Now for the lesson... The more you know, the more you realize how little you actually know... More coffee for me...

 

[KWentling]

This link (so far alone out of a dozen including 3 emails to Cummins) bore fruit! KUDOS to Rocky Mountain Cummins!!!!

Whaaaaaada a mess, don't know where to begin.
(I spoke to both girls working there today BTW, I don't feel empowered to name them). I think they desrve the parts-dept nobel award!

I now have half a mind to chuck the entire PAI kit and order me a Cummins kit as maybe I should have done in the first place.

Glad you got it figured out. I was afraid you weren't going to try calling them. I figured they could help you. They have been very good in my experience.

 

[fitterski]

Glad you got it figured out. I was afraid you weren't going to try calling them. I figured they could help you. They have been very good in my experience.

A local mechanic who was also 'on it' for me for an hour and came back with yet another set of numbers close to mine but not the same said 1-800-CUMMINS was where I "should have" called. But that was after I had gotten my set of numbers. Anyway thanks to your link it's all done, aimed for 0.018 all around with a few overshot to 19 & 20. Tomorrow the pistons go in.