Charles,
I shouldn't have inserted my posts into an existing thread and clutter it up so I'll repeat it here. BTW I wish you and all the G members and their loved ones a Merry Christmas and a great new year.
I pulled the #1 piston out of the M37 earlier and looked at the rings, the 3rd ring from the top, an oil control ring did not expand at all when the piston was removed from the bore and it barely moves around with my fingers, seems to be very sticky, the other 3 rings expanded and freely move in their slots. The 2 oil control rings are supposed to be the same part # but they are different, the sticky ring is the 3 piece type and the bottom ring is the single type. The piston was painted OD and has !-252 stamped on top. As mentioned in an earlier post the cylinders look good with no top ridges and the valves seal tightly, this engine had a compression of 115 to 119 about 5 years ago. Could the sticky oil control ring cause the compression loss? Any thoughts?
Yes sticking rings will cause that for sure. It is a good idea to check the bore measurement since you have a piston out to see if it is cone shaped, or larger at the bottom. It is typical to find that, even if a top ridge doesn't exist. If you find that to be the case, it to is playing a part in bad readings, and will require a bottom end rebuild at the very least to correct the issue. My first suggestion since you have found the stuck ring issue would be to add kroil penetrating oil liberally on top of the pistons letting it flow downward to the rings. It just may free them up bringing compression #'s back to an acceptable level. This condition would indicate either a lack of lubrication or the use of a poor quality lubricating oil. The better oils available these days make a huge difference in the occurance of issues like this. Standard off the shelf brands actually provide little protection; simply put, they ain't what they used to be, along with the dirtier fuels we get today adds to the extreme need for the best oils. The reason for this is basically, they use price to drive sales of the products, and not quality. People in general will jump on a low price thinking they are getting some sort of great deal on an older reputable product. Honestly, the sooner one realizes that bargains don't exist in this respect, the better. You get exactly what you pay for, end of discussion.
Thank you Charles. What about the stuck ring being a different style than the bottom ring? I checked a NOS set of rings and the two bottom rings should be the same.
greencom wrote:Thank you Charles. What about the stuck ring being a different style than the bottom ring? I checked a NOS set of rings and the two bottom rings should be the same.
All the current production ring sets we have installed in recent years are as you have pictured. The NOS stuff has been improved upon many times using today's technology, in most cases, just best you disregard the NOS stuff and go with much improved current production parts from a reputable manufacturer.
You may want to check the ring in question to be sure it was installed correctly. The center ring in the groove can overlap an extra notch at the end which will render it tighter in the groove than it should be. The possibility exist that could be the case making it appear as stuck.
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