Oil Ring Insanity

[n2omike]

Putting the oil rings on the 4.125" Mahle pistons in my 363. It has a support rail because of the pin height.
Anyway, the oil rings simply do NOT want to cooperate! The expander seems too large in diameter.

For a 4.125" bore, what should the free (butted up) diameter of the expander be? Mine measures around 4.140" and there is no way it wants to get installed on the piston, let along installed into a cylinder. I got it assembled the best I could, and tried to put it through a tapered ring compressor, and all it wanted to do was fail.

Do I have the wrong expanders?
I measured another (much older and different style) expander, and it was slightly less than the bore diameter.

Thanks!

[BillK]

Are they the real thin oil rings ? I know the ones that come with the Mahle Hemi pistons are very very hard to get on properly. Mahle has a pretty good tech guy for the performance stuff. I would give him a call. 888-255-1942

[n2omike]

Are they the real thin oil rings ? I know the ones that come with the Mahle Hemi pistons are very very hard to get on properly. Mahle has a pretty good tech guy for the performance stuff. I would give him a call. 888-255-1942

Thanks!
If it matters, these are the older Mahle pistons with the 1.5/1.5/3.0 mm ring pack.

[n2omike]

Alright... I called their tech line at 888-255-1942 and was told that for standard tension rings, the expander is actually supposed to be slightly larger than the bore. When inserted bare into the bore, it should have about a half segment of overlap... which it does.

The support rail is compounding things, as the bottom oil ring rail wants to duct under it. Seems like it could use a little more radial thickness or something. Or, maybe I just need more practice with these things... lol

[n2omike]

My advice for these (so far) is to install the oil ring only, then carefully use a tapered ring compressor on the bench to get the oil rings to take a 'set' in the compressor. You can use a pick to guide the rails from underneath. Once it is all correct inside the compressor, you can remove, install the other rings, and then carefully install the piston in the cylinder. Still have to be careful and not force anything, as the expander can un-butt and overlap. These are indeed a PITA. lol

[n2omike]

I've got a system now. It's slow, but it seems to work.

Install support rail and expander. As Brent said, hold the expander butted while the rails are installed. This can take a couple trials, as the expander comes completely out of the groove while installing the oil ring rails. The oil rail is also larger in diameter, and overhangs the support rail. Once I get things to where they finally feel right, I'll put the piston in a tapered compressor and push it through to get things 'set'. This will often call for a pick to poke the oil ring rail back into place over the support rail from underneath.

After this, the piston comes out and the top two rings are installed. Now, everything goes back into the tapered ring compressor. The piston is worked down until the pin boss is even with the bottom of the compressor where all the rings are compressed. Now, it is a loaded assembly, and is ready to go in the cylinder. Using the compressor outside the engine makes it possible to KNOW everything is right before trying to stuff the piston/rings into the cylinder.

Hope that makes sense. lol

I really appreciate the number for Mahle Tech. KNOWING it is supposed to overlap a half segment in the bore let me know that is was 'me' and not the parts. Never had oil rings fight me like that. lol

[cjperformance]

When the oil ring is like this it is actually easier to use a conventional ring compressor rather than the taper sleeve. The sleeve wants to twist the oil ring as you have found whereas the conventional compressor tends to pull the ring in square. Still a pain though.

[n2omike]

They're all done, installed and rod bolts torqued. Wow, this short block doesn't take much force at all to rotate. Digital torque wrench varied between 10-15 ft-lbs as it goes through its rotation... and these are the older Mahle pistons with the 1.5/1.5/3.0 ring package. The new ones come with 1.0/1.0/2.0 rings.

Rod side clearance came out to 0.016" to 0.017"... which I felt may be a little bit on the tight side, but don't think enough to be an issue.

I like to spray the rings/lands with WD-40 and use 2-stroke oil on the cylinders, as it is designed to lubricate rings and burn off cleanly.

Getting motivated!