Help / Brain Cells Request Continental O-300 Problem

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TFF

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Yes, check whatever the end part of the valve stem that rides in the guide for mushrooming. There might be a wear pattern that you can feel while rotating the valve that might be freer through the guide. Maybe you can determine if it feels bent.

I would move on to another cylinder to see the state of another one. If not all of them. Low hanging fruit first.

It will come down to the choice of skipping it all together or whacking it through, in the end. If you decide to skip it, maybe you can get something like Chemdip parts cleaner down the guild for some time and see if you can eject any gradu before you lube and put it back together permanently.
 

Aviacs

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Ex valve is reduced stem on O-300.
(Not a factor for mushrooming afa removal)

smt

edited: nevermind, read previous pages and see it has been addressed.
 

proppastie

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possible it is bent...?....if was stuck open is it interference with the piston top? ......look at all the fun you are having.
 

delta

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My guess is that carbon build up got it stuck. If that's the case, penetrating oil should do the trick. I bought a 280z one time with no compression due to old gas sticking the valves. I got 'em loose with wd-40 and "tapping" the stem with the springs on. This stuff BG Platinum® 44K® Fuel System Cleaner | BG Products, Inc. works miracles for varnish, and hopefully will do the trick for you.
 

PTAirco

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I had a similar experience with my O-300 powered Maule M4. Shortly after I bought it with about 900 SMOH, my friend borrowed the airplane and took off from Big Bear (6,700 elevation) . A few minutes later he texted me (I was at Flabob (760ft elev.) and said the airplane was climbing badly and vibrating. He scooted of over the lake at a couple of hundred feet and then it was downhill all the way to Flabob. It sounded horrible taxying in and when we checked the cylinder temperatures the two left rear ones were pretty cold. The rear exhaust valve was stuck but we didn't think anyone would be unlucky enough to get two stuck valves at once? Taking off the rocker covers, the rear was stuck but the middle cylinder seemed ok. Only later did I learn that with the stuck open valve, the intake mixture to the adjacent cylinder also gets contaminated and it will run badly too.

I did the rope thing and carefully cleaned up the guides with a ball hone, cleaned the valve stems, reassembled it and all was fine until a few days later when the same thing happened on the other side. Needless to say all the valves got the same treatment after that. No problems since then, but I think whoever operated the airplane before me never did use the mixture control much. I now lean it as soon as it starts to the point where it almost stumbles and leave it there until take off. And I lean the hell out of it at cruise. Since then about 200 hours with not a hint of a problem. Also ran a couple of pints of TCP through it. Whenever the stars align correctly I also add 2.75 glugs of MMO to the fuel, but rarely. Just makes me feel good, no idea if the engine likes it.
 

Victor Bravo

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And now... the latest !

We finally got the SECOND stuck valve out. This time we knocked it loose into the cylinder. It took a machined aluminum bushing that fit over the exhaust valve guide, machined to allow a modified long rivet set (mahcined down to be .020 less than the valve stem).

The bushing went on the guide, and the rivet set went into the bushing. The bushing held the rivet set tool in the center of the valve tip without it being able to move off-center.

The end of the rivet set punch tool was polished smooth so it did not scratch or gouge the valve tip.

The big end of the rivet set went into my rivet gun.

A heat gun was zip-tied to a tripod, pointing at the cylinder near the exhaust valve guide.

15 minutes later, the cylinder head wa too hot to touch easily. The compressor was turned on and the rivet gun trigger was pulled.

It took about 100 blows with the light rivet gun (1X), but the valve slowly got knocked into the cylinder.

Half an hour was allowed to let everything cool down to room temperature.

The valve stem was pushed up and out through the spark plug hole, and plenty of crud was cleaned up with a small brass Dremel rotary brush.

The special reamer was coated with grease and carefully run through the guide. The reamer came out with plenty of black crud.

My custom magnet-on-a-stick and wire hooks got the valve back out through the guide and into position, about 30 seconds of effort.

The valve slid in and out through the guide easily, with the exception of the last 1/4 inch of travel toward the fully closed position. It doesn't want to close completely except when the valve is rotated to one specific rotational position. My first thought was "oh s**t I bent the valve".

  • But the stem slides easily through most of the guide, with no wobble, rocking, or looseness.
  • When I spin the valve in my fingers and look through the spark plug hole, the edge of the valve seat does not wobble or move in an eccentric motion.

Neither of those things would likely happen with a bent valve.

So tomorrow/Saturday I will continue to look and see what is causing this.

But the George Foreman Knockout Punch tool worked as hoped for!
 

proppastie

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exception of the last 1/4 inch of travel toward the fully closed position
if it is not bent lots of lead crud forms on the radius of the head to the stem......and you probably were not able to get to it with the Dremmel wire brush through the spark plug hole.... safe way is to remove the cylinder if you can not get to it......not so safe way is to try some needle files or a small stone with the Dremmel through the spark hole but scratching the valve is not good and most assuredly that will happen.....also tube brushes

1642200335181.png brush.png
 
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TFF

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A rocker arm does not push down perfectly straight on the valve. There is a lateral component. I imagine that guide, valve or both might have “grooved”. If it didn’t wear we would never have any of these problems. I would probably pop the stem out the plug hole again. A little scotchbrite for a few minutes. Check the top of guide with the ream again. It’s good to be careful, you don’t have to work like an open heart surgeon. Act like a hack surgeon. Just make sure the valve gets back in.
 
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Aviacs

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Back in one of my early posts with all the pix, i documented a scraper made of aluminum bronze scrap.
Same material as many valve guides, maybe harder than some. But it will not scratch the valve stem.
To get it to fit in the sparkplug hole, the inner face is bored to the same radius as the guide stem. With the valve pulled up, it will reach the valve neck and works well enough. It can be "sharpened" with a file, too, if necessary.

1642210734382.png

954 Aluminum bronze is also ridiculously tough = it is not going to chip or shed particles down the cylinder.
The "Snagger" tool cable also tends to break up some of the looser, crustier carbon deposits.
 
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Victor Bravo

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Aviacs... NOW I understand what the bronze scraper is for ! I thought you used it to clean the guide, but now I see it is to scrape the valve stem. A-HA !!! I used a scotchbrite, a "chore girl" copper wool pad, and a small brass brush in a Dremel tool.

I did two of the cylinders this evening: Rope trick, keepers off, valve stem cleaned up of grunge, valve guide reamer, valve lapping compound, rinse with spray oil to wash out most of the gunk and lapping compound, reassembly.

The plan is to do all the cylinfders this way, then do TWO final spreay rinse operations using gasoline to make sure the lapping compound grit is all washed out and won't stay in the engine.

My funky custom wire hooks and magnet-on-a-stick tools are working very well. Getting the valve back through the guide has turned out to be the easiest part of the job.
 

Aviacs

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Glad everything is working for you!

While cleaning, be sure to get all the grease used on your reamer out of the guide, too. Other wise it will just turn to carbon.

smt
 

Victor Bravo

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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.
 
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proppastie

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I have no idea why some of them needed significant pressure on the reamer and some didn't
stuck oil ring......MMO (Marvel Mystery Oil)...after you are done squirt in to and leave in cylinder on the ones that were a problem. Worth a try...
 

Pops

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Put on a pair of bib overalls, and a pair of gum boots and a chew in his jaw and keep his mouth shut accept to spit he will be OK.

Keeping his mouth shut-- there is about 4 different dialects in WV. If he didn't talk with one of the dialects, they would know he's a foreigner.
Now, if he had a Lincoln County dialect, he would be top dog.
 
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