Camshaft question

Morgan3820

Morgan3820

Ejection Handle Pulled
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El Conquistador
I have an IO360-1C1 in my Arrow. Before I put money in the panel, I want to check the cam for goodness. Is there anyway to get an idea of the health of my camshaft with out pulling cylinders? As for the metal in the oil filter. A friend had a clean filter but had to rebuild due to a bunch of lobes being ground down to a nub. So while it may be an indicator, it is not infallible.
 
In one Continental I have been able to see a handful of cam lobes through the oil filler port using the Ablescope. (even that has limitations, however ie image quality and flat views vs being able to physically handle a lobe) Thinking about looking through a sump drain hole after the next oil draining.
You could pull a cylinder.
But yeah, oil analysis/oil filter inspection.
 
Morgan3820 said:
I have an IO360-1C1 in my Arrow. Before I put money in the panel, I want to check the cam for goodness. Is there anyway to get an idea of the health of my camshaft with out pulling cylinders? As for the metal in the oil filter. A friend had a clean filter but had to rebuild due to a bunch of lobes being ground down to a nub. So while it may be an indicator, it is not infallible.
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Pulling 2 cylinders is not an inexpensive venture. There is a Lycoming SB for pulling the rocker covers and push rods and measuring lift.
 
You can measure the lift without pulling pushrods. Since you're not after a yellow tag inspection on the part all you want to do is verify that the lobes are all more or less the same. Bad ones will read enough smaller that you should see it. Normally there will be a couple really different if there is going to be excessive wear so if they're all within close measurements you should be fine. If you are really concerned pulling one or two jugs may be worth the money.
Procedure is use a dial indicator attached to a steel bar with a screw to attach to one of the cover retaining points. Set the tip of the indicator shaft on your rocker....it doesn't matter which end, you're looking for differences rather than absolute measurements. Just make sure you measure the same point on all 6 cylinders. If you are really into it you can measure the distance from the center of the rocker shaft to the point you measured and figure out total lift on the cam lobe. Once you're done compare all the intakes and all the exhausts. If you see some big differences than pull a jug. If they're all very close you can be happy.

This is still a bit painful especially if you've got to hire a mechanic to do it for you but its cheaper and simpler than pulling the jugs.

Frank
 
Yes, this is what I was thinking. As You said, I am just trying to get an idea of things before I spend bucks on the panel.
 
How about engine history? It sounds like it may have some years since overhaul? Then how were those hours and sit times spread out?
 
Be aware that pulling jugs is not only expensive, but it's major engine surgery that carries with it not insignificant risks of "maintenance induced failure." I wouldn't pull a cylinder unless I had a real reason to believe I had a problem; I don't think "exploratory surgery" is worth the risks.
 
What’s to gain? If you believe your engine needs work? Work on it. If not? Don’t. Bottom line? Every engine in every airplane will need to be overhauled eventually. If yours is running good there’s no reason to rush it.

Do you have a mechanic you trust? Talk to him.
 
Stewartb said:
What’s to gain? If you believe your engine needs work? Work on it. If not? Don’t. Bottom line? Every engine in every airplane will need to be overhauled eventually. If yours is running good there’s no reason to rush it.

Do you have a mechanic you trust? Talk to him.
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This is the best advice. I wouldn't mess with it until it needs fixing.

Personally, I don't think a person is going to get a positive enough indication of cam/tappet condition by checking valve lift to make it worth the effort. Too many variables involved that can influence the outcome.
 
mondtster said:
This is the best advice. I wouldn't mess with it until it needs fixing.

Personally, I don't think a person is going to get a positive enough indication of cam/tappet condition by checking valve lift to make it worth the effort. Too many variables involved that can influence the outcome.
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Actually, that it the method for checking cam wear. What variables are there that would disguise a rounded off bumpstick?
 
Kenny Phillips said:
Actually, that it the method for checking cam wear. What variables are there that would disguise a rounded off bumpstick?
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These have hydraulic lifters. You going to be able to see the proper lift with a lifter bleeding down? I think not. Plus there is the fact that the cam might just be slightly worn. That won't be detected like it would be if the cam and tappet are severely worn.

I've done a lot of valvetrain testing at work, measuring lift in running engines, etc. I can tell you we have performed zero tests that were 100% conclusive. Some things can be observed, some can't be detected as easily.
 
BiffJ said:
You can measure the lift without pulling pushrods. Since you're not after a yellow tag inspection on the part all you want to do is verify that the lobes are all more or less the same. Bad ones will read enough smaller that you should see it. Normally there will be a couple really different if there is going to be excessive wear so if they're all within close measurements you should be fine. If you are really concerned pulling one or two jugs may be worth the money.
Procedure is use a dial indicator attached to a steel bar with a screw to attach to one of the cover retaining points. Set the tip of the indicator shaft on your rocker....it doesn't matter which end, you're looking for differences rather than absolute measurements. Just make sure you measure the same point on all 6 cylinders. If you are really into it you can measure the distance from the center of the rocker shaft to the point you measured and figure out total lift on the cam lobe. Once you're done compare all the intakes and all the exhausts. If you see some big differences than pull a jug. If they're all very close you can be happy.

This is still a bit painful especially if you've got to hire a mechanic to do it for you but its cheaper and simpler than pulling the jugs.

Frank
Click to expand...
Your method would be fine for a solid lifter engine. However with hydraulic lifters, it would seem that they would leak down when the valve is open and recover when the valve is shut. This could cause measurement inaccuracies, and they may not be consistent between lifters as the leak down rate can vary. What I have done is remove the rocker arms and then measure the travel of the push rod with a dial indicator mounted as you suggested . With essentially no load on the lifter it will be a constant length and a reliable measurement of the cam lobe is assured.
 
NordicDave said:
Surprising that engine made max RPM with the lobe worn that far.
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Well, min RPM, and just barely. It was a noticeable change from the static RPM 75 hours previously, enough to investigate further. Differential compression was good but cranking compression was lousy, so we pulled the jug.

BTW, 1999.5 hrs SMOH, 4200 TTSN, but it had been "topped" (really just a honing and valve job) at 1700 SMOH. Replaced with Lycoming new, modified by Firewall Forward Centrilube STC.

https://firewallforwardengines.com/stc/
 
It takes a lot of cam wear to affect immediate engine performance. But on the other hand, just a little cam wear means the carburized cam surface has broken down and the engine is being filled with steel.
 
NordicDave said:
Does the engine make static power? If so, likely a good cam.
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The Arrow has a C/S prop, but I do made 30" MP at take off field elevation of 16', density altitude was about 1500', if that helps. Found zero debris on the tempest oil filter magnet. Looking at the engine log now. It was a factory overhaul at 1856 hrs. in January 1998. So that makes it 23 years to the first overhaul and twenty years, 924 hrs. SMOH on this overhaul. Latest compressions, just done 2 weeks ago are 75/80, 74/80, 74/80, 77/80. Bore scoped the valves and all were symmetrical with no green edges. As camshafts can be an issue, I am just looking for some reassurance about the engine before I throw money at the panel.
 
bradg33 said:
Be aware that pulling jugs is not only expensive, but it's major engine surgery that carries with it not insignificant risks of "maintenance induced failure." I wouldn't pull a cylinder unless I had a real reason to believe I had a problem; I don't think "exploratory surgery" is worth the risks.
Click to expand...
Oh you read mike bush BS about never changing a cylinder because it’s so dangerous.
 
nrpetersen said:
It takes a lot of cam wear to affect immediate engine performance. But on the other hand, just a little cam wear means the carburized cam surface has broken down and the engine is being filled with steel.
Click to expand...

Probably won’t find it in the filter, the cam is being grounded down, not coming apart in chunks except for a pieces on the edges, oil analysis might show elevated iron.
 
Paulie said:
Oh you read mike bush BS about never changing a cylinder because it’s so dangerous.
Click to expand...

That's a bit of an extreme take on what I said. If you read my comment a little more carefully, I simply stated I wouldn't make the decision to pull one "lightly." I also didn't say it's necessarily "dangerous," but you're a fool if you think that pulling and replacing doesn't carry with it not insignificant risks of maintenance induced failure.
 
Maintenance induced failure. Let’s all just buy new engines, oh wait, a guy had to assemble it, that could cause a failure. Jeez.
 
Paulie said:
Maintenance induced failure. Let’s all just buy new engines, oh wait, a guy had to assemble it, that could cause a failure. Jeez.
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Actually, if the cross-bolts are improperly torqued (which turns out is easy to do; at least, it's easy to mistake improper torquing for proper torquing due to several factors) the main bearing crush will be less than spec, the bearings will "walk" and possibly spin, thus blocking off the oil supply. What happens next is a short period of loud noise followed by silence. This has happened, more than once.
The most common "maintenance induced failure" is probably not removing the old oil filter gasket (they sometimes stick to the engine) before replacing with a new filter.
 
Per Piper MM you actually set high RPM using the prop governor during static runs.

Generally on a Cessna, when you do static runs the prop should act as a fixed pitch prop, stuck on the low pitch stop and the engine should not turn max/redline RPM, instead a range given in the maintenance manual. If the engine can't make that range it is not making rated power. Also, to set the high RPM limit on the prop governor you have to do takeoff runs to see when the governor is kicking in and what RPM runs then make adjustments accordingly.
 
Kenny Phillips said:
Actually, if the cross-bolts are improperly torqued (which turns out is easy to do; at least, it's easy to mistake improper torquing for proper torquing due to several factors) the main bearing crush will be less than spec, the bearings will "walk" and possibly spin, thus blocking off the oil supply. What happens next is a short period of loud noise followed by silence. This has happened, more than once.
The most common "maintenance induced failure" is probably not removing the old oil filter gasket (they sometimes stick to the engine) before replacing with a new filter.
Click to expand...

How many engines have you topped or how many cylinders have you replaced?

Most of what you wrote is, in my opinion, more Busch garbage. He loves to paint with a broad brush and imply that all mechanics (except for himself of course) are inept and crooks.

I have seen problems resulting from cylinder replacements. The percentage of problems compared to the number of cylinders I've seen R&Rd is so small that it is hardly worth mentioning.
 
mondtster said:
How many engines have you topped or how many cylinders have you replaced?

Most of what you wrote is, in my opinion, more Busch garbage. He loves to paint with a broad brush and imply that all mechanics (except for himself of course) are inept and crooks.

I have seen problems resulting from cylinder replacements. The percentage of problems compared to the number of cylinders I've seen R&Rd is so small that it is hardly worth mentioning.
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What is Busch? NM, looked it up, seems he copped stuff from a major manufacturer of horizontally opposed, air cooled, reciprocating aircraft engines, which is where I read it. Similar cautions come from other engine makers, including automotive, about "gotchas" that are quite easily missed.
I never said "don't pull the jugs"; I just said that there are effective, more conservative checks to make that are less expensive and less invasive (someone said that measuring cam lift at the rockers wouldn't work. And yet it's done all the time, hydraulic tappets or not.) Of course, if one makes their money doing surgery, they tend to recommend surgery.
 
Kenny Phillips said:
What is Busch? NM, looked it up, seems he copped stuff from a major manufacturer of horizontally opposed, air cooled, reciprocating aircraft engines, which is where I read it. Similar cautions come from other engine makers, including automotive, about "gotchas" that are quite easily missed.
I never said "don't pull the jugs"; I just said that there are effective, more conservative checks to make that are less expensive and less invasive (someone said that measuring cam lift at the rockers wouldn't work. And yet it's done all the time, hydraulic tappets or not.) Of course, if one makes their money doing surgery, they tend to recommend surgery.
Click to expand...

You'll see in my first post in this thread that I advocated doing nothing. That is the safest course, why disturb what is working? When you go looking for trouble hoping you don't find it you're almost guaranteed to be disappointed.

My experience has been that maintenance induced failures is not the major concern everyone makes it out to be. Sure there is a risk opening up an engine but the risk is minimal. The "gotchas" you speak of are not as "quite easily missed" as it is made out to be. I have seen exactly one aircraft engine that had problems after having a cylinder replaced. Those problems were created due to improper torque, specifically on the through bolts. There were no rolled bearings and the engine didn't blow up. In fact, as far as I know that engine still lives on after the same cylinder was replaced for a second time. It is common knowledge (and common sense) that you'd want to torque all associated hardware.

Engines are far more durable and resilient than most people believe. What we do with them in the test lab I work in would make many people shudder.
 
Mike bush makes a living off of scaring people that do not have a intimate knowledge of airplanes. Nothing wrong with not knowing about aircraft, nobody can know everything about everything.
To me, someone with more than 40 years in the aircraft maintenance industry, bush strikes me as one of those guys with a radio talk show attempting to scare people to make a buck. He may be a excellent mechanic but his tactics are that of a hack.
He’s one of those “only I can save you, everyone else is incompetent and trying to rip you off” bs artists.
Any magazine that carries his column is of no use to me.
I’ve noticed that Sport Aviation has really been dumbed down recently too.
I have no skin in this, I’m a A&P, IA but I don’t make a living off it, most my work is gratis for friends. I make way more being a independent aviation technical writer (maintenance manuals) and I sit at home without getting dirty.
 
OP wants to know if he should focus on the panel at the risk of needing to replace a bad cam.

Sounds like nothing factual is causing you concern about the cam (or all the facts/data are “normal”). If all appears and runs well, focus on the panel.

Your other choice is to build up your engine reserve before jumping into the panel, just for conservatism-sake.

Go fly the p*ss out of it and stop worrying about the cam. I worry about gremlins in my machine all the time, I’m an expert at it.
 
If it ain't broke....then there's nothing to fix. Agreed. ;)

If it were something to worry with.....there'd be an AD on it. Stop worrying and go fly.
 
Sky Ranch Engineering Manual describes how to properly inspect the filter for cam wear debris. it involves rinsing the filter media in solvent and using a strong magnet to pull steel out of the solution. I'd wait for 50 hours and check the filter that way. Or, send a filter to Second Oilpinion, they do filter rinsing.
 
When I bought my plane the engine had 1600 hours SNEW, I was prepared to need an overhaul, I’m now at 2200 hours, I was lucky. If I start to see metal or compressions drop, I won’t hesitate. Once I realized the engine was good, then I updated the panel. You might want to fly it as is till the 1st annual, after that you’ll have a good idea of what you have and what you need.
 
TJ, check to see if your plane does book speeds vs fuel flow. If it does, the cam is fine. As Frank states above, valve lift on a Lycoming is reliable because Lycoming lifters, as I understand, rarely collapse. Keep in mind that there are only six cam lobes because a couple of the intakes are shared. They are doing double duty so they should be the ones wearing first. You have a way to validate your readings on these shared lobes by checking their lift on multiple cylinders.
 
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