N201MKTurbo Posted June 20, 2014 Report Posted June 20, 2014 Maybe I missed something, but why not simply replace cam, lifters and rings? Then go on your way for the next 1000 hours or so. We fly Mooney's because we are cheap! If we had that kind of money to throw around we would fly a Beech! (I'm going to rot in hell for that one) 2 1
KSMooniac Posted June 20, 2014 Report Posted June 20, 2014 Maybe I missed something, but why not simply replace cam, lifters and rings? Then go on your way for the next 1000 hours or so. I chose a Firewall Forward "drilled camshaft" for my engine. So far, the lobes look great (via borescope up through the oil drain) and no significant iron in the UOA's. I tore my engine apart at 21xx hours after measuring a failing cam (#1/#2 intake lobe). Instead of opting to exchange (more like play craps) for a factory engine, I'm overhauling what I had and taking extra special care to make everything as perfect as possible. It saves a lot of money, but adds a lot of downtime, so that needs to be understood up front. Centri-lube cam (as in the picture above), precision balanced crank, rods, and pistons, flow-matched cylinders with precision valve cuts, flow-matched lifters, etc. All to tighter tolerances than Lycoming specs, and *I* know what is going into it. My first-run cylinders just needed a hone, and my crank just needed a polish so nothing was cut/ground for oversized parts. Case overhauled just fine and got the extra dowels to prevent fretting. I don't get a roller cam/lifters, but then again I think that configuration solves a problem that *isn't* present in Lycomings, so I don't want to pay extra for it. The warranty is on me too of course, but I'll be starting with more than 10 AMU extra in the bank, so to speak, compared to a factory exchange so I'm willing to play the odds. /knocking on wood. The next best option IMO is to send the engine to a top-shelf engine shop and they could probably turn it a lot faster than I'm doing mine, at greater cost of course.
aaronk25 Posted June 20, 2014 Author Report Posted June 20, 2014 Is there any way to go to a seperate mags instead of the dual mags if I don't go with a factory engine?
KSMooniac Posted June 20, 2014 Report Posted June 20, 2014 Is there any way to go to a seperate mags instead of the dual mags if I don't go with a factory engine? Not easily... I'm not paranoid about the dual mag setup, but it requires checking the security of the mounts at each oil change, and 500 hour IRANs. The overall configuration is lighter than the split mag set up too. I understand the concerns and don't blame anyone for switching, though. It may be possible to locate the different accessory case and other internal gears to make a conversion in the field, but I didn't even try.
aaronk25 Posted June 20, 2014 Author Report Posted June 20, 2014 I'm not concerned either about the single mags reliability, just that there is no easy way to set the interal timing vs seperate mags.....they always get a couple degrees off and I can hear it in flight. Also was considering a electro air electronic ignition because I spend most of my time between 9-15k ft.
Sabremech Posted June 20, 2014 Report Posted June 20, 2014 I think the short answer, especially with aircraft engines, there are no guarantees. Sure, you can do all the things everybody talks about, but a part of the equation, and not an insignificant variable IMHO, boils down to luck and rolling the dice. Sorry you are having the bad luck on this one! +1. There are no guarantees with additives or methods of operation to totally eliminate a failure. Sorry to hear this happening to you. It will most likely be me some day as I don't use any of the additives or fly regularly. I guess I'll find out some day. David
KSMooniac Posted June 20, 2014 Report Posted June 20, 2014 The dual mag is reliable if you get a good shop to put it together... the internal timing should not be drifting IMO. In over 700 hrs of operating mine I never adjusted timing at all. It was freshly overhauled before I bought it, and i had it off for a 500 hr inspection once a couple hundred hours ago. 2
N201MKTurbo Posted June 20, 2014 Report Posted June 20, 2014 The dual mag is reliable if you get a good shop to put it together... the internal timing should not be drifting IMO. In over 700 hrs of operating mine I never adjusted timing at all. It was freshly overhauled before I bought it, and i had it off for a 500 hr inspection once a couple hundred hours ago. You had to adjust the timing if you took the mag off. I would suggest at least checking the internal timing every time you have the mag off. It only takes a few minuets. Adjusting it is another story, depending how picky you are.
pinerunner Posted June 20, 2014 Report Posted June 20, 2014 Scarey, the third guy I talked to about Mooney's (when I was shopping for one) told me a story of camshaft failure. I'm beginning to think its a major boogeyman of the IO-360. What about the carburated C models. Do they see this just as much?
Skybrd Posted June 21, 2014 Report Posted June 21, 2014 It is no coincidence that the lifter that failed was associated with the cylinder that was using excessive oil. The cam and lifter are bathed in hot corrosive blow by gases when the ring seal is compromised. I haven't heard this before but it makes sense. My former M20e had the same thing happen. Low time SMOH engine developed low compression in the number 2 cylinder. When the mechanic pulled the cylinder he found the associated cam lobe pitted and the lifter spalled. If hot leaking gasses from stuck rings caused it, wouldn't this problem show up more. BTW this problem caused the engine a complete tear down and it ended up being exchanged for a rebuilt Lycon engine.
carusoam Posted June 21, 2014 Report Posted June 21, 2014 Welcome aboard to GMerrel. Sounds like you have some deep technical knowledge. Best regards, -a-
Marauder Posted June 21, 2014 Report Posted June 21, 2014 We fly Mooney's because we are cheap! If we had that kind of money to throw around we would fly a Beech! (I'm going to rot in hell for that one) You may still rot in hell for the comment, but your standing in the Cheap Bast$)d has risen significantly. Sent from my iPad using Tapatalk 1
DaV8or Posted June 21, 2014 Report Posted June 21, 2014 I tore my engine apart at 21xx hours after measuring a failing cam (#1/#2 intake lobe). Instead of opting to exchange (more like play craps) for a factory engine, I'm overhauling what I had and taking extra special care to make everything as perfect as possible. It saves a lot of money, but adds a lot of downtime, so that needs to be understood up front. Centri-lube cam (as in the picture above), precision balanced crank, rods, and pistons, flow-matched cylinders with precision valve cuts, flow-matched lifters, etc. All to tighter tolerances than Lycoming specs, and *I* know what is going into it. My first-run cylinders just needed a hone, and my crank just needed a polish so nothing was cut/ground for oversized parts. Case overhauled just fine and got the extra dowels to prevent fretting. I don't get a roller cam/lifters, but then again I think that configuration solves a problem that *isn't* present in Lycomings, so I don't want to pay extra for it. The warranty is on me too of course, but I'll be starting with more than 10 AMU extra in the bank, so to speak, compared to a factory exchange so I'm willing to play the odds. /knocking on wood. The next best option IMO is to send the engine to a top-shelf engine shop and they could probably turn it a lot faster than I'm doing mine, at greater cost of course. I don't get it? Don't Lycomings have a problem with spaling camshaft and lifters? Don't roller lifters solve this? What problem do roller lifters solve that isn't present in Lycomings?
pinerunner Posted June 23, 2014 Report Posted June 23, 2014 Did you get a look at the valve stems and guides on this cylinder? Could there have been a bit of sticking which would dramatically increase the stresses between the cam lobe and lifter? This seems to be one of the nastiest problems we're likely to run into with our IO-360's and any trick to catch and nip it in the bud would be invaluable. I don't buy the notion that its just dumb luck. There must be a way to catch it if only we can sort it out.
KSMooniac Posted June 23, 2014 Report Posted June 23, 2014 I don't get it? Don't Lycomings have a problem with spaling camshaft and lifters? Don't roller lifters solve this? What problem do roller lifters solve that isn't present in Lycomings? Roller lifters are more helpful in high RPM applications, which our engines most certainly are not. Lycoming engines have two major weaknesses IMO... lack of direct lubrication to the cam/lifter interface, and to the valves. That is why we see failed cams and lifters, and sticky/failed valves so often. The Bravo mod does to the M20M engines would be extremely helpful for the IO-360 as well. Centrilube or Ney Nozzle mods to get oil to the cam are also helpful.
DaV8or Posted June 23, 2014 Report Posted June 23, 2014 Roller lifters are more helpful in high RPM applications, which our engines most certainly are not. Lycoming engines have two major weaknesses IMO... lack of direct lubrication to the cam/lifter interface, and to the valves. That is why we see failed cams and lifters, and sticky/failed valves so often. The Bravo mod does to the M20M engines would be extremely helpful for the IO-360 as well. Centrilube or Ney Nozzle mods to get oil to the cam are also helpful. I may be misled, but I thought the main problem was corrosion forming on the camshaft due to inactivity. If this is true, then the central lubrication scheme and the Ney Nozzles my help some, but the cam will still do many revolutions until the oil pressure comes up and circulates. I would think there is still the potential for compounding damage over time. Roller tappets may be preferred in high RPM engines, but do they not more or less solve the problem of camshaft corrosion none the less? They seem to me to be the best solution to our 360 engines short of a complete redesign. Having said that, if I were to have to rebuild due to a rotten cam and I didn't want to spring the money for a new engine with roller tappets, I would be pretty tempted by the drilled camshaft I think. I'd have to do some serious research on that first though.
KSMooniac Posted June 23, 2014 Report Posted June 23, 2014 The roller tappets don't do anything to address the lack of cam lubrication... the cam still sits up high, out of the oil, and without a direct oil path so it still has the same potential to corrode if left sitting for some period of time. I did opt for the drilled cam mod for my overhaul, and I'm going to add a pre-oiler as well, so hopefully I'll oil much, much closer to the cam lobes before I turn the key. Hopefully that helps longevity, but only time will tell. It is just a band-aid to help a design defect IMO.
jetdriven Posted June 23, 2014 Report Posted June 23, 2014 I may be misled, but I thought the main problem was corrosion forming on the camshaft due to inactivity. If this is true, then the central lubrication scheme and the Ney Nozzles my help some, but the cam will still do many revolutions until the oil pressure comes up and circulates. I would think there is still the potential for compounding damage over time. Roller tappets may be preferred in high RPM engines, but do they not more or less solve the problem of camshaft corrosion none the less? They seem to me to be the best solution to our 360 engines short of a complete redesign. Having said that, if I were to have to rebuild due to a rotten cam and I didn't want to spring the money for a new engine with roller tappets, I would be pretty tempted by the drilled camshaft I think. I'd have to do some serious research on that first though. That's kinda what I was thinking as well. The iron lifters get corrosion which is scrubbed off at engine start. Then micro pits form which turn into spalling. When you catch it early enough it's always the lifter that goes first. In fact, Continental engines you can swap in new lifters and save the camshaft. Not that roller lifters can't rust, but they are hardened steel and roll on the cam instead of slide.
N201MKTurbo Posted June 23, 2014 Report Posted June 23, 2014 When I opened up the engine on my first Mooney in 1984, it had seriously pitted and dished lifters. The cam lobes were seriously warn. That airplane was a hanger queen when I bought it. It was 20 years old and had less then 1000 hours on it. I had the cam and lifters re-ground. (I was 27 years old and strapped for cash). The cam and some of the lifters were from unknown sources (yellow tagged). I have never seen the slightest hint of cam wear or corrosion sense then. I think it takes some serious disuse to cause the type of problems that I saw on that engine.
jetdriven Posted June 23, 2014 Report Posted June 23, 2014 Can you explain Aaron's issue then? He flew it every few days with camguard etc and it still got a spalled lifter. Ours flew regularly for 10 years then flew 75 hours then 35. Then we flew it 250 hours in a year and 3 lifters were trashed.
KSMooniac Posted June 23, 2014 Report Posted June 23, 2014 I'm in a similar boat... I opened mine at 1650 and cam & lifters looked fine. Fast forward a few years and 500 hours and I lost most of a lobe and two lifters, others had some pits starting. I'm guilty of letting mine sit now and then up to a month, but it is hangared and I was using Camguard. I think it is part luck-of-the-draw, part usage patterns, and part climate/location.
N601RX Posted June 23, 2014 Report Posted June 23, 2014 There are a few other factors that could be in play also. There could be a sticking valve or a lifter that is not rotating as it goes up and down. Back when car engines were all flat tapet cams all of the cam companies had warnings on their cams that said the 1st 30 minutes of use on the cam would largely determine if it would have a long life or not.
N201MKTurbo Posted June 23, 2014 Report Posted June 23, 2014 Maybe I'm just lucky. Maybe it is because I live in Arizona. Up until the last two years, I flew the plane almost daily. Maybe that's it. It would be interesting to survey engine shops from different parts of the country and see if there is a regional difference.
yvesg Posted June 23, 2014 Report Posted June 23, 2014 Aaron, was your aircraft parked outside or inside during the winter? The climate you have is similar to here I presume. I am wondering if your winter startup procedure might have anything to do with this? Yves
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