Broken piston ring? (longish)

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   Ok chaps.  Not wishing to sound too gloomy but I have a problem with my M635.  Just swapped out head for a fully rebuilt one.  Car runs very strong all through the rev range but has an annoying "ticking" sound.
The noise is a light metallic ticking at all engine speed (speed related).  I have carried out the following tests which I think are pointing towards a broken/cracked piston ring.
Compression test (warm engine, throttle fully open, igintion and fuel disabled, 7 cranks on engine.)
188,186,185, 185, 184, 185 - obviously very very good.  No oil consumption, no smoke out of exhaust.  So no problems with compression, maybe a leak down test would show something?  Plugs when removed are all a light brownish colour as expected. Maybe 2nd compression ring that has gone?
Ticking noise is present at idle as well but when HT lead is removed from cylinder 6, ticking noise disappears.  I assume from this that the rings /piston become unloaded and hence why the noise is not present?  Also this may point to a piston ring/exhaust manifold problem and not a head problem as the loading on the valve train would not be really affected by removing the HT lead?
Stethoscope seems to incidicate ticking from cylinder 6 as well.  I can also hear the noise with the stethoscope in the exhaust manifold on cylinders 4,5 and 6 but not on the maninold for cylinders 1,2 and 3.
All valve clearances are spot on, buckets move fine.  Head has new valve guides, 3 angle job etc.  Exhaust manifold bolts are all secure although I have not changed out the exhaust manifold gaskets yet but with the noise being so regular at most loads hot or cold I don't think it is the exhaust manifold that is at fault.
The ticking noise is annoying but not yet worrying.  Noise can be heard in the driver seat but is tending to be drowned out when listening from above engine with all those 24 hammers at work.
Does anyone have experience of what to expect from a broken piston ring in terms of noise.  Any other tests I could do to determine the problem?
Car has JE pistons and total seal rings, 2*schrick 272's and goes like stink all the way to the redline.
Sorry for the long post but I wanted to get all the info down.
Thanks
Ian 

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ian M635UK Members Profile Send Private Message Find Members Posts Add to Buddy List Really Senior Member I Joined: 01-July-2004 Location: United Kingdom Status: Offline Points: 264	Post Options Post Reply Quote ian M635UK Report Post Thanks(0) Quote Reply Posted: 08-September-2006 at 14:43
	Ok chaps. Not wishing to sound too gloomy but I have a problem with my M635. Just swapped out head for a fully rebuilt one. Car runs very strong all through the rev range but has an annoying "ticking" sound. The noise is a light metallic ticking at all engine speed (speed related). I have carried out the following tests which I think are pointing towards a broken/cracked piston ring. Compression test (warm engine, throttle fully open, igintion and fuel disabled, 7 cranks on engine.) 188,186,185, 185, 184, 185 - obviously very very good. No oil consumption, no smoke out of exhaust. So no problems with compression, maybe a leak down test would show something? Plugs when removed are all a light brownish colour as expected. Maybe 2nd compression ring that has gone? Ticking noise is present at idle as well but when HT lead is removed from cylinder 6, ticking noise disappears. I assume from this that the rings /piston become unloaded and hence why the noise is not present? Also this may point to a piston ring/exhaust manifold problem and not a head problem as the loading on the valve train would not be really affected by removing the HT lead? Stethoscope seems to incidicate ticking from cylinder 6 as well. I can also hear the noise with the stethoscope in the exhaust manifold on cylinders 4,5 and 6 but not on the maninold for cylinders 1,2 and 3. All valve clearances are spot on, buckets move fine. Head has new valve guides, 3 angle job etc. Exhaust manifold bolts are all secure although I have not changed out the exhaust manifold gaskets yet but with the noise being so regular at most loads hot or cold I don't think it is the exhaust manifold that is at fault. The ticking noise is annoying but not yet worrying. Noise can be heard in the driver seat but is tending to be drowned out when listening from above engine with all those 24 hammers at work. Does anyone have experience of what to expect from a broken piston ring in terms of noise. Any other tests I could do to determine the problem? Car has JE pistons and total seal rings, 2*schrick 272's and goes like stink all the way to the redline. Sorry for the long post but I wanted to get all the info down. Thanks Ian

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