Help / Brain Cells Request Continental O-300 Problem

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Victor Bravo

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Attaching some photos, rather clumsy to have to e-mail them from my phone and then upload from the desktop, so bear with me....

This is the exhaust valve during the cleaning process. Green Scotchbrite, "Chore Girl" copper sponge, and a brass rotary brush in the Dremel tool. The rope is inserted through the lower spark plug hole, which is quite a bit more of a PITA than the top hole. I finally figured out that surgical sponge clamps (giant hemostats with the loop ends) would force the rope into the hole form below much faster than I could wrestle with it using my fat fingers.

Rope Trick #1.jpg


This is the hi-tech equipment I borrowed from Rube Goldberg Scientific Supply Co. (a division of Acme Products). A molded rubber elbow hose connected to a smaller hose that slid tightly over the top of the valve guide. This was filled with the acetone/ATF mixture, and held from spilling by the unused end of the rope. The heat gun was borrowed from a friend, and installed using zip ties to a small piece of copper tube, which was slid into the receptacle of a portable halogen light tripod with the light removed. It gets better... in order to hold the copper tube at the right height (from slipping down into the tripod) a small C-clamp was used on the copper as a stop. I'm anxiously awaiting my Nobel Prize for Science notification letter, likely co-signed by someone named MacGyver, Mr. Goldberg, and his UK licensee Heath Robinson.

Rope Trick #3.jpg


Another glamour shot of the gravity-powered Penetrant Oil Dispensing System, along with the Aluminum and Bronze Thermal Heating & Expansion system.

Rope Trick #2.jpg


Two mug shots of the perpetrator of this heinous crime. The hero of the day was the McFarlane special cleaning reamer, with Lubri-Plate grease, which apprehended and imprisoned the perpetrator... some nasty black gunk that took a little effort to get out of the guide.


Rope Trick #4.jpg


Rope Trick #5.jpg


This is the aluminum bushing that my friend made, slips over the outside of the valve guide and keeps "Rocco the Ramrod " from going where I don't want him. (Rocco is my mob enforcer, a turned down long rivet set that is about .020 smaller than the valve stem).

Rope Trick #6.jpg


More photos when I find them.
 

Victor Bravo

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I don't have a photo yet, but I lived up to my "stage name" The Great L. Cheapo, and made up a special tool using a small C-clamp cut in half.

I riveted the clamp section onto a piece of 1" or 1.25"square aluminum tube. This was all a desperate move to not have to pay the $45 for a much nicer version of this same tool at Aircraft spruce.

A long 1/4-20 bolt (with a large fender washer under the head) goes through the square tube, and the bolt threads into the rocker box cover mounting hole next to the exhaust valve. A small Micarta spacer goes under the small round C-clamp "foot". The tube is moved around until the Micarta pad is positioned on the valve spring retainer, and the bolt is snugged.

Then you screw down the C-clamp t-handle until the Micarta compresses the valve spring slightly. This takes the pressure off of the rocker shaft, allowing the rocker shaft to slide out halfway, and the rocker falls off into your hand.

Then the custom Rube Goldberg tool is removed, and you are able to install a larger "valve spring compressor" lever to get the keepers off the valve stems.

I may buy the nicer and prettier ACS tool anyway Rocker Arm Shaft Removal Tool | Aircraft Spruce , but I had the interesting experience of designing and making this custom one work, so it may have strengthened by brain cells against premature decay for another few minutes.
 
Last edited:

Bill-Higdon

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Feb 6, 2011
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Location
Salem, Oregon, USA
Attaching some photos, rather clumsy to have to e-mail them from my phone and then upload from the desktop, so bear with me....

This is the exhaust valve during the cleaning process. Green Scotchbrite, "Chore Girl" copper sponge, and a brass rotary brush in the Dremel tool. The rope is inserted through the lower spark plug hole, which is quite a bit more of a PITA than the top hole. I finally figured out that surgical sponge clamps (giant hemostats with the loop ends) would force the rope into the hole form below much faster than I could wrestle with it using my fat fingers.

View attachment 120667


This is the hi-tech equipment I borrowed from Rube Goldberg Scientific Supply Co. (a division of Acme Products). A molded rubber elbow hose connected to a smaller hose that slid tightly over the top of the valve guide. This was filled with the acetone/ATF mixture, and held from spilling by the unused end of the rope. The heat gun was borrowed from a friend, and installed using zip ties to a small piece of copper tube, which was slid into the receptacle of a portable halogen light tripod with the light removed. It gets better... in order to hold the copper tube at the right height (from slipping down into the tripod) a small C-clamp was used on the copper as a stop. I'm anxiously awaiting my Nobel Prize for Science notification letter, likely co-signed by someone named MacGyver, Mr. Goldberg, and his UK licensee Heath Robinson.

View attachment 120669


Another glamour shot of the gravity-powered Penetrant Oil Dispensing System, along with the Aluminum and Bronze Thermal Heating & Expansion system.

View attachment 120668


Two mug shots of the perpetrator of this heinous crime. The hero of the day was the McFarlane special cleaning reamer, with Lubri-Plate grease, which apprehended and imprisoned the perpetrator... some nasty black gunk that took a little effort to get out of the guide.


View attachment 120670


View attachment 120671


This is the aluminum bushing that my friend made, slips over the outside of the valve guide and keeps "Rocco the Ramrod " from going where I don't want him. (Rocco is my mob enforcer, a turned down long rivet set that is about .020 smaller than the valve stem).

View attachment 120672


More photos when I find them.
I'll give you an Ignobole pries for the use of a heat gun by some acetone
 

Victor Bravo

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Oh, there was motor oil and transmission fluid present too, and avgas within arm's length. I figured that I might qualify for Nobel and Darwin simultaneously :)

(seriously, my hand was constantly placed on the cylinder to monitor the temp from the heat gun, and I verified none of the acetone/ATF mixture was dribbling out of the valve guide hose attachment... I'm a bit slow but not quite that slow)
 
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Update: All six cylinders are now "rope trick"-ed. THREE if the valve guides were clear of any crud, and the reamer slid in without having to turn it. These three cylinders were not all on the same side, nor were they all in front or rear. I have no idea why some of them needed significant pressure on the reamer and some didn't need the reamer at all.

I did the lapping compound, and this lapping operation resolved all of the valves that did not want to close all the way, or the ones I was not able to easily turn by hand when they were closed.

Heat from a heat gun to warm up the valve guide area made a noticeable difference. Flooding the "stuck" valves in the guides with 50/50 acetone and ATF fluid also helped significantly. On the ones that still needed my rivet gun tool, they needed fewer and lighter blows with the rivet gun than without the heat and penetrant.

I saved a lot of aggravation removing cylinders but I now have to spend some time removing the exhaust and intake systems, to allow me to wash out the cylinders with gas/oil mixture to get the lapping grit out.

As with everything else in aviation, if I had it to do over again tomorrow with what I know now... it would take 1/3 of the time.

Will update this thread with photos, viudeo, etc. once I can get it all into a format that will be helpful to others.

In general, I found the "rope trick" is not nearly as scary as it seems to people who have not seen or done it.... after you do it a few times. But the fiirst time you see and hear your valve loose inside the cylinder, you will have a "WTF did I just do ?!?!" moment for sure.

If we take the Mike Busch videos and his opinions as being highly credible and wise, then this is indeed a far better alternative to taking the cylinders off because of stuck or leaking valves.
Mike never puts his name in a logbook for any work like this, that should tell you something.
 

Victor Bravo

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Mike's videos are the ones with the recommendation that you avoid removing the cylinders whenever possible. He makes a very good case for why you should exhaust other options before just pulling the jugs off.

I'm not sure what you're saying he is unwilling to put in the logs.

Concerning the actual nuts and bolts of fixing the problem, what is the right method (for a mechanic, engine shop, FBO, or amateur) for repairing stuck valves, while heeding Mike's advice of not removing the cylinders?

Anyone can simply give up, remove the cylinders and send them out to be replaced or overhauled. That is certainly appropriate when your cylinder is worn out, no compression, cracked, etc. But these cylinders are still making compression and simply had clogged valve guides. And on top of that, removing/replacing the cylinders on the aircraft is now supposed to be seen as a higher risk.

So, to borrow a phrase from a popular bumper sticker... "What would Mike do?"
 
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Victor Bravo

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UPDATE: 1-22-2022

Spent hours removing the intake and exhaust system components from BOTH #*$& sides of the engine to get clear, safe access to the cylinder base nuts (previously removed cylinder) and the other side of the through-bolts (undisturbed side of the engine). This is a real PITA on certain small parts on the O-300. One of the three plain hex cap screws that hold each intake manifold to the side of the oil pan is a very awkward SOB to get a wrench on. Half an hour of fighting and flipping a 7/16" ignition wrench over and back twice to get the bolt head turned by one flat. The little AN primer fittings in that same small area also require a lot of wrench flipping and screaming, getting your wrist bruised between the oil pan, the engine mount, and the intake manifold.

Once everything was out of the way, I loosened the (previously removed) base nuts, and ran them back far enough to get the lubricating oil all over the threads, nut face, and cylinder base flange to be able to re-torque them the way Continental wants.

Also took that opportunity to put a socket on all of the exposed nuts that are hidden or blocked by the intake system.... the tappet body covers, the oil pan attach nuts, etc. Nothing was badly loose, but a couple of nuts torned several degrees, so I'm happy to have had the opportunity to reach them.

Next trip to the airport I will lube and re-torque the base nuts. Then I'll re-torque the base nuts on the other side of the two through-bolts, just in case something moved.

I have another somewhat interesting puzzle on the O-300. If people think it should be spun off into a separate thread let me know.

Has anyone investigated, quantified, or resolved the uneven fuel distribution on the O-300 created by those horrendous intake manifolds?

Some of my valves stuck and others were free and clear. This is telling me that some cylinders are getting more fuel/lead/carbon/heat/cooling than others, which is probably a contributing factor to the stuck valves.

The intake system appears to be the only serious "lost opportunity" on the O-300; it's simple, reliable and very smooth - but there sure looks like there's a lot of lost power or poor fuel economy they just accepted back in the 1940's, in order to have a quick and dirty five dollar cast aluminum manifold. The manifolds on the "big Continentals" are entirely different.
 

TFF

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EFI.

My friend put a full engine monitor on his carbed Lycoming and ever sense he has been scratching at its itch because it shows all the sins. Certified so stuck with what it says. Move your plane out of certified and you can do something.

Sounds like you are close to being back.
 

Pops

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Direct fuel injection and install C-85 pistons, light weight starter and alternator. The GO-300 used in the C-175 in the last year also had a CS prop. There are fruit to pick.
Having owned 3 different straight tail C-172's , I like the 0-300 engine , just wish that it had at least 20 more HP. In my work C-172 , I needed the smoothness for all the camera's . I had a 0-300 MOH'ed by an old engine builder and it was by far the strongest , smoothest 0-300 engine I have flown.

Hopped up C-300 in a Tailwind would be nice.
 

TFF

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If you got the money , the STC for the Continental 360 on a C175. The 172XP is actually the continuation of the 175. Same TCDS.
 

Dan Thomas

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Has anyone investigated, quantified, or resolved the uneven fuel distribution on the O-300 created by those horrendous intake manifolds?
Some of my valves stuck and others were free and clear. This is telling me that some cylinders are getting more fuel/lead/carbon/heat/cooling than others, which is probably a contributing factor to the stuck valves.
Probably not on an old engine like that. GAMI has one it on many fuel-injected engines and they sell a kit of injectors sized to maintain the same fuel/air ratio in every cylinder. It solves some of the carbon fouling problems and makes the engine run a bit smoother.

Sticking valves are sometimes caused by running the engine too rich for too long. Lean it out more; that will get the exhaust valves hotter and burn off the varnish, or prevent its formation in the first place.
 

Victor Bravo

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I'm well aware of the STC's for Continental IO-360 and Lycoming O-360. Both of those are much larger or more expensive projects than I want to invest in right now. Nine grand for the paperwork on the Del-Air Lycoming conversion, before any parts are purchased. Never checked, but I'm sure "Tailwheel Tom" Anderson is not shy about the IO-360 paperwork either.

I am also very well aware of the Ly-Con and other 8.5-1 pistons, and I would definitely ask Santa Claus for a set of those if all of my cylinders ever had to come off.

But the uneven fuel distribution that is likely coming from those intake spiders is still going to affect the cylinder temps, valve guides, power levels, etc. no matter what the compression ratio is.

The (later development) GO-300 has a different intake system, and I am guessing that this was an attempt to overcome the shortcomings of the previous intake system (O-300 A-D). The G engine mounts the carburetor further back on the sump, runs the in take charge forward through a long duct inside the sump, and has a large loop of 2.5 or 3 inch diameter intake runner duct/tube that runs around the entire perimeter of the engine (including a balance tube connecting the ends of the loop). For whatever you can tell from looking, it looks more efficient and looks a lot closer to what they used in the larger/later engines like the 470.

So I spent some time last night trying to determine if the GO-300 intake system could be retrofitted to the O-300. But the oil pan on the G engine has a deviation in the mating surface that the O engine doesn't have. So from a quick look at Google Images, it appears I can't just swap out the parts.

But I could potentially modify a junkyard O-300 sump to operate the same way as the G sump, and then fairly easily create the loop. These parts would bolt on and bolt off, so if it doesn't work I have not ruined a good engine.

However, there is also an equally valid chance that the O-300 cast aluminum intake is better than it looks, and that the fuel distribution is not as bad as what I am having nightmares about, and that I could be embracing a concept that is not nearly as big a deal as it seems. So before I think about going down that rabbit hole, I am trying to find out whether anyone else has flow- benched it, tested it, modified it, etc. etc. etc.
 

Victor Bravo

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Probably not on an old engine like that. GAMI has one it on many fuel-injected engines and they sell a kit of injectors sized to maintain the same fuel/air ratio in every cylinder. It solves some of the carbon fouling problems and makes the engine run a bit smoother.

Sticking valves are sometimes caused by running the engine too rich for too long. Lean it out more; that will get the exhaust valves hotter and burn off the varnish, or prevent its formation in the first place.
Thanks for that Dan. Another problem that I have learned about is that partial throttle operation contributes greatly to this issue, because the angle on the throttle butterfly alone causes lopsided patterns everywhere downstream of it. I've always tried to run as low power setting as adequate for the job at hand... "baby-ing" the engine to reduce the mechanical and cyclic stresses. Now I'm finding out that this causes some issues involving greater temperature variations from one cylinder to another.

Ironically, these valve sticking issues just started shortly after I began leaning the engine out in flight as much as possible... to reduce fouling!
 

Dan Thomas

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Thanks for that Dan. Another problem that I have learned about is that partial throttle operation contributes greatly to this issue, because the angle on the throttle butterfly alone causes lopsided patterns everywhere downstream of it. I've always tried to run as low power setting as adequate for the job at hand... "baby-ing" the engine to reduce the mechanical and cyclic stresses. Now I'm finding out that this causes some issues involving greater temperature variations from one cylinder to another.

Ironically, these valve sticking issues just started shortly after I began leaning the engine out in flight as much as possible... to reduce fouling!
Babying the engine does it little good. It's certified to produce its rated power for its entire TBO life, unless it has a five-minute restriction on full power, as some larger engines do.

Breaking in an overhauled engine requires running it a high power levels for several hours. Lycoming has an SL on it, and when I replaced engines in the flight school airplanes I did that procedure. Basically, you take off a soon as possible once the engine has warmed a bit, climb at full throttle to a fairly low cruise altitude where the engine will still make 75% percent power, and hold it at 75% for an hour. Then a second hour, varying between 65% and 75%. Then a half hour at full throttle, keeping the RPM at redline and the temps in the green. Airplane sure scoots along like that. This hard running puts plenty of pressure on the rings, forcing them against the cylinder walls and making them mate well with those walls. Oil consumption will be low after that. Babying the engine lets the rings glaze the walls, and they'll never seal properly, losing oil, fouling plugs, lowering compressions, increasing blowby into the case, dirtying the oil and increasing moisture in there.
 

TFF

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No one thought you were going to bite on a $40,000 conversion with used parts. It’s the game of trying to save relative to what?. A Volksplane or a 182? You are doing everything as frugal as reasonably possible unless you change everything. If there was something out there, you would have already known about it and either already had it or would be lusting.

To “fix”, make it better for a certified plane, would require a stack of parts. You would probably need 20 plus cylinders, pipes, oil pan, and map them all on a flow bench where you helped the down cylinders and hurt the good ones with that mix of parts. There is probably some legal overhaul grinding possible. Essentially a race motor that the race is even cylinder operation. Not most power. That one off line cylinder on each side messes up the balance. You could fade the crank throw for each cylinder when having it ground undersize; for each throw custom to placement. “Clean” the manifold with abrasive milling. It would be a big development project. Another way to spend $40,000 and it still wouldn’t be great.
 

Pops

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Old friend of mine and Dallas built a C-200 for Dallas's 1966 C-150. The builder ( Ed) built 0-200's for pylon racers for many years. He said the engine was completely legal in every way, BUT , I never seen a 0-200 perform like that one. Climbed better than an C-150 that I ever flew and would cruise side by side with a C-172. The exhaust sound had a stronger bark at idle.
I owned the same 1966 C-150 two times. C-150 Patrol that had the long range fuel tanks and the HD nose gear. Had a climb prop and the cruise was about 95 mph with the climb prop.
 
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Mike's videos are the ones with the recommendation that you avoid removing the cylinders whenever possible. He makes a very good case for why you should exhaust other options before just pulling the jugs off.

I'm not sure what you're saying he is unwilling to put in the logs.

Concerning the actual nuts and bolts of fixing the problem, what is the right method (for a mechanic, engine shop, FBO, or amateur) for repairing stuck valves, while heeding Mike's advice of not removing the cylinders?

Anyone can simply give up, remove the cylinders and send them out to be replaced or overhauled. That is certainly appropriate when your cylinder is worn out, no compression, cracked, etc. But these cylinders are still making compression and simply had clogged valve guides. And on top of that, removing/replacing the cylinders on the aircraft is now supposed to be seen as a higher risk.

So, to borrow a phrase from a popular bumper sticker... "What would Mike do?"
I have been to both TCM and Lyc schools and so far they have not come out with any SL or SB condemming pulling and replacing cylinders. In fact, if you saw how they built up engines on the floor, I would have to say that Lyc is more anal about maintaining case tensions than TCM was..
Now, i have only done like one or two cylinders in my 46 years of plane wrenching, and on some engines it is a major pain, others relatively simple( respectively) process. Dangerous?? NO. Invasive?? Thats someone else's term. For any good shop or mechanic, this is just part of maintenance. So if you have a cracked cylinder... would mike say weld it on the engine?? Some of his "recommendations" are just downright out in left field and dangerous. My co horts feel the same way. Doing valves 'in sit' is not a bad idea, BUT, if you really have a whole top end that needs it done, who are you kidding. Nobody in my circle pulls cylinder for fun. People, there are NO easy and CHEAP fixs sometimes on 40 and 50 year old planes. What i have seen is way too many shade tree mechanics and owners/builders that just don;'t know any better. And yes, even cylinders installed with RTV for base seals. ( wish i had phot of those) Are there good mechanics? Yes, are there clueless ones?? Yes. As evidenced that it took me 2.5 years and 26 airplanes to finally find a 172 worth buying.
I don"t know the Quals of the person or persons doing this work but one thing i can say of the "mikes" of our profession , if you really researched backgrounds, you would find they really have not the experience that many Organizations have proported they have.
They have no problem telling a owner or mechanic what to do, but THEY are not taking any responsiblily for the work. AND responsiblily is what you pay for. The analysis parts they are good at and and they have some good recommendations for troubleshooting and perhaps finding a quality shop to work with . Sadly , it is hard to find a good mechanic, or at least one trained by a good mechanic or IA.
Our profession does not tolerate sloppy work.
Oh, as mentioned on one of the threads on limiting lead build up,,, if you went to Lycoming school, they teach you that leaning on ground is practically useless,,,, UNLESS you have at least 1200 rpm,, ,they found that is the MIN rpm that provides enough HEAT to burn off lead.
In 2o year of Alon flying before my 172 now, Never had lead fouling. Frequent oil changes too. The Lyc o235 doen;'t make enough heat to do toast. Its a lead generator.!
Does any one know what Lyc recommends for oil change intervals??
Excuse my long winded ness.
 
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