Dumbest question I think I've asked. Can you see broken rings with a borescope?
 

I have my 3.2 intake off my 3.4, and I was wondering if I can see a broken ring or not using a borescope.

I've used many back in the day on F15 jet engines, but never in a reciprocating.

Why I'm looking into, is I developed mild blowby after a overboost (hit 30PSI) mishap. Just want to prove what I think has happened.

No, but you may be able to see scoring on the cylinder walls using the spark plug hole to go in.

Broken rings will generally remain encapsulated in the ring groove and stay captured between the piston and cylinder wall. The only way you can see broken rings with a borescope through the spark plug hole is if the piston has failed badly...

Nikasils will get scored? Figured the coating is tough enough this wouldn't occur? I don't think I've had enough detonation to blow the crown(s) since the plugs looked pretty clean - meaning no missing ground straps or chunks of aluminum bits on the plugs.

My 79 3.3 had some when I tore it down a few weeks ago.

You think you ran it for quite awhile?

No, I purchased the car a few months ago, previous owner put about 5k on it in 25 years.

It didn't run right, did all the usual plugs,wires, cap & rotor and run the valves. I found seven broken head studs, got 23 out of 24 removed. Ended up splitting the case and found more problems and now Ollies machine shop has most of the engine.

I'm now waiting for their evaluation and estimate.

Cory, you probably already know this, but you can more or less verify broken ring(s) by doing a leak-down test on all of the cylinders and listen for hissing in the oil tank, and/or engine drain plug hole, if you find cylinders with higher than normal leakage.

Surprisingly, broken rings do not always reduce leakdowns so that's not a reliable test.

The only real way to know is by disassembly.

Ronnie, to what Sir Steve said, made me think of a borescope. Heard people have fine leakdown, but still found broken rings.

Of course, the gap between the crown and cylinder is so tight, figured it wouldn't work.

But, thought maybe there was a slim chance someone knew something I didn't.

When I had broken rings there was an increase in oil usage:

My engine leaks so much, I wouldn't know Craig. HEHE

Cory & Steve, I didn't know that - thanks for the schooling. :)

My memory is terrible, but when I hear something that seems to defy physics, I generally remember. Having broken rings with good leak down seems crazy, but have heard members experience this here.

Broken rings definitely scored my Nikasil cylinders. One to the point of needing replating.

Broken rings will eventually cause damage and scoring. The fact that there is more then one a leakdown test may prove OK as long as the damage is recent. As time goes by scoring on the cylinder will affect the sealing of all the rings even if they are not broken and of course oil consumption will start to increase. Would have to be a good scoring. If there is oil leakage then your plug could start to foul. I drove a Toyota 4x4 22r for 26 years. One time I was cruising along and suddenly alot of clattering in the engine and then stopped. I pulled over checked it out and finding nothing continued on my way. Over the next 6 months this would happen give me a heart attack and then go away. A boroscope would have told the tale. Finally the engine on its last tired legs got me home for the last time. That day I was blowing oil out of every orfice. When I pulled it apart the banging was the piston breaking apart. The truck ran well until it started breaking into the last ring land and then it oil ring. I basically had direct passage to the sump from combustion chamber. Good old 22r. Goodluck Thanks Rob

^not that there's any doubt when Steve says it, but I can confirm this from personal experience. I found broken rings on 3 cylinders when I rebuilt my '79 930 engine. Two had good leakdown and compression numbers:
https://asbury.smugmug.com/By-Land/M...SC_3852-XL.jpg
https://asbury.smugmug.com/By-Land/M...SC_3846-XL.jpg
The "bad" cylinder was #6. Compression was about 10psi down vs. the others, and leakdown was 40%. Surprisingly the engine ran very well, no noticeable smoking. Oil consumption was a bit high (one clue) and the car had a pulsed puffing of vapor from the oil filler neck (another clue).
#6 in addition to broken rings had a deformed crown. Ring lands were deformed such that one was tight and the ring could not rotate, and another was very loose so the ring could flutter. You can also see the oil cooked on the piston crown of #6 above the top ring. An obvious difference between that piston and the others, that's where the blow by and oil consumption was occurring.
https://asbury.smugmug.com/By-Land/M...SC_3847-XL.jpg

Jacob, how did the cylinders looks? Any scoring. That thing looked like it ran awhile in that condition.

It possibly ran for years in that condition. The cylinders all looked decent IIRC. They measured slightly out of factory spec, but there wasn't any nasty looking surface damage, and the crosshatch was intact. I put new cylinders in anyway because I increased displacement to 3.5, as that was my plan all along I didn't spend a lot of time inspecting them to be honest. I gave them to Brian B (RarlyL8) when he was putting together a mock up "mule" engine to test fit his parts to.

Ok, thank you Jacob. Good to know my precious cylinders (if a ring or two or three!) has a chance of not being trashed. :eek: