What are the running characteristics of broken piston rings?
 

Is there a noticeable symptom that indicates a broken piston ring?
What is it? Generally, which ring is prone to break, top, middle, or oil control ring?

I was just dicussing stuff like this with Tyson at TRE this morning. It seems to me a leak down might divulge issues like broken rings, but even that isn't definitive.

Loss of oil perhaps? Smoking on decel? Is anything like that occurring?

Great question, movin. I'd be interested in the answer. You might also want to post this on the 911 Engine Rebuilding forum.

only guessing,
top piston land gets worn. so I figure the top ring is more likely to break.

Off the top of my head, a low compression test reading might be an indication and/or increased blowby.

Sherwood

I think it's the sound of your credit card number being typed in at Pelican, the UPS man ringing your doorbell and lots of shouting.

I had detonated /overheated the top ring, piston lay, and 2nd piston ring on my #1 and the top ring on #2 cylinders on a '73 2.7 motor before.

It smoked REALLY REALLY bad.... On acceleration more than decelleration.

Good luck.

An oily spark plug.
 

Pull your plugs and have a look. It is a good indicator of this problem.

John

I just had this happen to the corvair. Biggest clue was excessive oil consumption. Increased crankcase pressure, and NO compression in #6. Complete disassembly revealed both compression rings were broken and managed to scar the cylinder wall pretty good.

Yeah, it's using oil (500mi/qt), but like others smokes a little at start-up then settles down, smokes a little on acceleration, and accumulates a light brown film on the valence around the exhaust pipe after about 1000mi. I don't really see hardly any smoke and looking at the plugs there's no indication anything is wrong, it's like the oil is being spit out of the exhaust ports. If I drive it hard the oil consumption goes up (400mi/qt). Could oil be sucked down the exhaust guides? If so then during positive pressure the oil is blown back up into the cam towers, and during evacuation/low pressure it's being sucked into the exhaust ports?