mattbucy Posted May 13, 2015 Report Posted May 13, 2015 Borescoped my engine last weekend while I had the plugs out. IO-360-A3B6D has almost 1700 hours on it over 32 years with pretty even usage annually. It's lived in the northeast almost all of its life. Wondering if the cylinder pitting, corrosion, scrapes that I'm seeing are typical for an engine this age or something to wonder about. Oil analysis is good, no metal in filter, operation smooth, compressions in low 70s, oil consumption is about 5hrs/qt, cylinders run cool (around 300F). Any expert eyes out there? (By the way, one cylinder was pulled and overhauled before I bought this plane for some reason. It's the one with the crazy scratches that I guess were a re-hone. Looks terrible to me. But, maybe that's what an overhauled cylinder looks like. Anyone know? I've asked my mechanic to look, too. Curious about other opinions.) Thanks! M Quote
Alan Fox Posted May 13, 2015 Report Posted May 13, 2015 They look horrible , but if it is making power , let it go.....The cam probably looks similar......The rust in the pics is from extended periods of sitting....probably the peeling chrome also..... Quote
Guest Posted May 13, 2015 Report Posted May 13, 2015 Certainly aren't the prettiest cylinder walls. Don't forget that magnification makes it look even worse. What type of borescope did you use for the pictures? Clarence Quote
ryoder Posted May 13, 2015 Report Posted May 13, 2015 I want to borescope mine. What did you use and how do you do it? Just stick a can into the plug hole and move it around? Quote
1964-M20E Posted May 13, 2015 Report Posted May 13, 2015 I had 2 & 4 off to change the base o rings over the weekend not that bad but I could see some things we honed them a and put them back on. I should have taken pics but i did not. I'd run it. I've seen different engines with worse run for a long time. YMMV how long have you had the plane? Quote
aerohawk Posted May 13, 2015 Report Posted May 13, 2015 If it is making good power I would say let it go. The scratches and corrosion by it self won't prevent it from making tbo. But at 32 years old I would overhaul at tbo since there is moe then likely corrosion on the crankshaft. Quote
M20F Posted May 13, 2015 Report Posted May 13, 2015 i would consider pulling a cylinder and looking at the cam given the years/time. Engines sometimes make some metal, run rough, or otherwise indicate a problem is coming. Many times though they suck in a valve, chop a ring, have a lobe break off, etc. when everything was perfect just five seconds before. I believe in IRAN but the key is really being aggressive when it comes to the I part. Quote
PTK Posted May 13, 2015 Report Posted May 13, 2015 Did you look at the valves? How are oil filter inspections? Any spectroscopic oil data? They don't look bad to me. It's making rated power so don't worry about it. Quote
Hank Posted May 13, 2015 Report Posted May 13, 2015 These scratches are not a problem, they are from the initial honing of the cylinders (the crosshatch visible in some photos is desirable, indicative of good work). Yes, there is some corrosion starting, but it don't know how much is too much--talk to an A&P who you trust. To me, it doesn't look too bad, but I'm just an engineer/machinist and private pilot. If it's making power, has good compression and good oil analysis results, keep going, although 32 years since overhaul is a long, long time. Quote
M20F Posted May 13, 2015 Report Posted May 13, 2015 Mine has consistently very high compression (all cylinders at or above 78/80), 5 to 6 hours per quart oil burn rate, and clean filters, but internally probably looks a lot like yours. If it ain"t broke, don't fix it. Compression and oil consumption are only two of many factors in determining engine health. Wear on the cam, valves, etc. shows up in oil analysis when aggressive in nature but you can have a cam or valve wear over time that will give no indication until it breaks off. Visible inspection is a key tool especially when things get old and when you don't know the complete history of how the plane was maintained and flown over decades. Time is at some point going to cause a sudden failure of a part and in many instances there will be no indication prior from a normal operational sense. We all need to carefully balance the idea that while a set of mags could operate for 5000hrs with no issue, at some point logic needs to dictate perhaps digging deeper in inspection or replacing before that items failure leads to a much more costly problem. Quote
mattbucy Posted May 13, 2015 Author Report Posted May 13, 2015 Thanks for comments. I used a SnapOn BK8000 borescope. It's got two integral cameras and lights on a flexible probe, one camera off the end of the probe and the other 90-degrees. It requires getting close to things to see well, so yes, the pix are extreme close ups. Valves look fine, symmetrical deposits and coloration. Stems are a bit gunky. Seats are clean and mostly shiny with some mild corrosion. Oil filter is always clean and oil analysis shows nothing unusual over three years of samples. It produces plenty of power. It drinks a fair amount of oil, 4-5 hrs/qt. Compressions are above 70. My A&P is looking at pix too. I'll let you know what he says. Sent from my iPhone using Tapatalk Quote
mattbucy Posted May 13, 2015 Author Report Posted May 13, 2015 My mechanic got back to me. Says just watch the oil for signs of wear and fly it! Nothing else warranted despite age. With all the pitting he says the oil consumption is to be expected. Makes sense. A lot of oil is being left in the pits each stroke. I would be tempted to pull a jug to see what's up with the cam but yeah it's invasive. I've always been someone who loves to take things apart. Wish there were some way to take a peek that didn't require surgery. Sent from my iPhone using Tapatalk 1 Quote
KSMooniac Posted May 13, 2015 Report Posted May 13, 2015 I wish we could add a borescope hole in the crank case to inspect the cam and crank... Sent from my VS985 4G using Tapatalk 1 Quote
Piloto Posted May 13, 2015 Report Posted May 13, 2015 Just because you have a couple of wrinkles and gray strands does not mean you are unable to fly. What is important is how you perform. If it runs good leave it alone. It has proven to be a good engine. But if you are obsess with borescope inspections why don't you try a colonoscopy. José 2 Quote
mattbucy Posted May 13, 2015 Author Report Posted May 13, 2015 I've got one of those coming up next month! Sent from my iPhone using Tapatalk Quote
Piloto Posted May 13, 2015 Report Posted May 13, 2015 I've got one of those coming up next month! Sent from my iPhone using Tapatalk Post pictures of your rectum here to get the experts opinion!!! José 3 Quote
MB65E Posted May 13, 2015 Report Posted May 13, 2015 The top photos look fine. The cross hatching is still there. The bottom 4 have some scoring and corrosion. Lycomings will tend to have good compression even when everything else is shot. I would keep an eye on oil consumption and continue to fly it. No doubt the oil is bypassing a bit, so keep fresh oil in it if your able to. I'd try to change it every 3mo & 20hrs. My compressions were great, valves were shot, valve guides were done, can had some nasty corrosion but the engine made no metal. We new something was going on because the oil would turn black in about 6hrs... Just fly it, -Matt Quote
mattbucy Posted May 13, 2015 Author Report Posted May 13, 2015 Matt, did you replace the engine eventually? What triggered it? Sent from my iPhone using Tapatalk Quote
Marauder Posted May 13, 2015 Report Posted May 13, 2015 Post pictures of your rectum here to get the experts opinion!!! José Absolutely! For all we know you have a redundant colon. Then we will know if you are full of it. http://www.healthline.com/health/redundant-colon#Overview1 Sent from my iPad using Tapatalk 1 Quote
MB65E Posted May 14, 2015 Report Posted May 14, 2015 Hi Matt, yes I majored it after finding the famous #2 lower cylinder case crack. I went to change the starter and the crack was found under the starter motor. Not much was saved in the engine. Crank, one rod, sump, rocker tubes, pushrods, and rear case. Everything else was scrap. It actually was running well. Inactivity killed it I believe. 1200hrs/20years. -Matt Quote
mike_elliott Posted May 14, 2015 Report Posted May 14, 2015 My mechanic got back to me. Says just watch the oil for signs of wear and fly it! Nothing else warranted despite age. With all the pitting he says the oil consumption is to be expected. Makes sense. A lot of oil is being left in the pits each stroke. I would be tempted to pull a jug to see what's up with the cam but yeah it's invasive. I've always been someone who loves to take things apart. Wish there were some way to take a peek that didn't require surgery. Sent from my iPhone using Tapatalk Have you thought about having your MX measure the lift of each lobe, particularly the shared lobes? That might give you some sleeping comfort. Quote
mattbucy Posted May 15, 2015 Author Report Posted May 15, 2015 Mike: good idea. Matt: good to know. Thx. Sent from my iPhone using Tapatalk Quote
Yetti Posted May 16, 2015 Report Posted May 16, 2015 My mechanic got back to me. Says just watch the oil for signs of wear and fly it! Nothing else warranted despite age. With all the pitting he says the oil consumption is to be expected. Makes sense. A lot of oil is being left in the pits each stroke. I would be tempted to pull a jug to see what's up with the cam but yeah it's invasive. I've always been someone who loves to take things apart. Wish there were some way to take a peek that didn't require surgery. Sent from my iPhone using Tapatalk pull rocker covers. measure valve lash. if your cam is going south gaps will be out of spec Quote
jetdriven Posted May 16, 2015 Report Posted May 16, 2015 Hydraulic lifters have zero lash. Plus the base circle of the cam doesn't wear. You have to measure the lift. And it only tells you when a lobe is grossly worn. Not just spalled 1 Quote
Yetti Posted May 16, 2015 Report Posted May 16, 2015 yep which is why large furry creatures should not drink and post, I was thinking of my motorcycle which is not hydraulic lifters and would probably like the valves adjusted about now Quote
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