Van's Air Force
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Exhaust Valve
- Thread starter RVadmirer
- Start date
I did it on a Continental C-85. I was at a fly-in. Fortunately, a valve guide reamer was available to me. The mechanics at the FBO, just happened to be there on Saturday morning. I did it with just a few hand tools I carried in a small tool kit in my airplane, and a piece of rope. I went to a local hardware store and purchased the mechanical fingers so I could manipulate the valve once I knocked it out of the guide. I would recommend a small magnet to help get the valve spring keepers out. I picked them out with a tiny screwdriver. It was a fight while holding the valve springs compressed, with another tool.
This happened to me 500 miles from home. It is really amazing what can be accomplished with not very much in the way of tools, and a willing helper or two. This happened at Jackson, CA. I flew the plane to Modesto later that day, then home to Eugene, Oregon the next day. The engine ran another 1100 hours without trouble .
This happened to me 500 miles from home. It is really amazing what can be accomplished with not very much in the way of tools, and a willing helper or two. This happened at Jackson, CA. I flew the plane to Modesto later that day, then home to Eugene, Oregon the next day. The engine ran another 1100 hours without trouble .
I can tell you about the technique for an 0 200 Continental. I suppose other
engines would be similar.
Remove the spark plugs on the offending cylinder. Bring the piston to TDC and move it down an inch or so.Start feeding a 1/4" rope into the cyliinder. when you have filled the cavity slowly rotate the prop to compress the rope against the exhaust valve. Having removed the valve cover, use a spring compressor to remove the valve spring retainers. Reverse the rotation of the prop and remove the rope from the cylinder and to allow space for the valve.
Spritz the valve stem with penetrating oil and gently tap the valve with a soft hammer, eg brass. The valve will fall out into the cylinder. With a light directed into the bottom plug hole, capture the end of the valve stem and pull it out through the top plug hole. Remove the buildup on the stem with penetrating oil and a very fine crocus cloth.
Get an adjustable reamer and set it the slightest amount bigger than the id of the valve guide. Lubricate the reamer and run it down the guide, keeping it aligned with the bore. Inspect the guide to see if all the carbon has been removed. if so, run a paper towel down the guide to clean up the stuff from the ream job.
Try the valve in the guide, you do this by inserting a piece of safety wire with a semi circle bent on the end at a right angle into the valve guide..Insert a second safety wire with a semi circular loop on its end into the top plug. capture the valve stem near the head, as you do this ,capture the stem end of the valve with the other wire. carefully guide the valve stem back into the guide. If it moves smoothly, reinsert the rope into the cylinder and reinstall the valve springs and retainers. By the way, you need to hold the mini mag light in you mouth to illuminate the cylinder as you are capturing the valve for reinstallation.
After all of this, reaming guides is usually a temoprary fix. The primary reason that valves stick is because they are worn and combustion byproducts are driven into the guide. I believe also that Lycoming engines have a tendancy to bell mouth the guides, which again allows carbon to travel into the guide and causes sticking valves.
engines would be similar.
Remove the spark plugs on the offending cylinder. Bring the piston to TDC and move it down an inch or so.Start feeding a 1/4" rope into the cyliinder. when you have filled the cavity slowly rotate the prop to compress the rope against the exhaust valve. Having removed the valve cover, use a spring compressor to remove the valve spring retainers. Reverse the rotation of the prop and remove the rope from the cylinder and to allow space for the valve.
Spritz the valve stem with penetrating oil and gently tap the valve with a soft hammer, eg brass. The valve will fall out into the cylinder. With a light directed into the bottom plug hole, capture the end of the valve stem and pull it out through the top plug hole. Remove the buildup on the stem with penetrating oil and a very fine crocus cloth.
Get an adjustable reamer and set it the slightest amount bigger than the id of the valve guide. Lubricate the reamer and run it down the guide, keeping it aligned with the bore. Inspect the guide to see if all the carbon has been removed. if so, run a paper towel down the guide to clean up the stuff from the ream job.
Try the valve in the guide, you do this by inserting a piece of safety wire with a semi circle bent on the end at a right angle into the valve guide..Insert a second safety wire with a semi circular loop on its end into the top plug. capture the valve stem near the head, as you do this ,capture the stem end of the valve with the other wire. carefully guide the valve stem back into the guide. If it moves smoothly, reinsert the rope into the cylinder and reinstall the valve springs and retainers. By the way, you need to hold the mini mag light in you mouth to illuminate the cylinder as you are capturing the valve for reinstallation.
After all of this, reaming guides is usually a temoprary fix. The primary reason that valves stick is because they are worn and combustion byproducts are driven into the guide. I believe also that Lycoming engines have a tendancy to bell mouth the guides, which again allows carbon to travel into the guide and causes sticking valves.
Something tells me this part also involves some language not suitable for small children.
I'm not sure if it's appropriate to these engines, but they do make stiff brass brushes for cleaning up valve guides. You can chuck em in a drill and give em a quick spin.
I used the spring loaded mechanical fingers to manipulate the valve once it was in the cylinder. You don't have to worry about dropping the valve. I aligned the stem with the guide and carefully used the piston to push the valve into the guide.
After getting home, I treated my fuel with TCP on a regular basis. I didn't have any more trouble.
After getting home, I treated my fuel with TCP on a regular basis. I didn't have any more trouble.
Kyle Boatright
Well Known Member
This brings back memories. I learned the rope trick at SnF one year in the GA campground at the West end of the field. A couple of slightly inebriated folks came over, asked if I had any tools they could borrow because they needed to repair a sticky valve. What I had was very limited, but it was enough (except for the reamer they had borrowed from a someone earlier in the day) In a couple of hours they dropped the valve, reamed the guide, and reasembled everything. Most of this was by flashlight with me peering over their collective shoulders.
I was impressed.
I was even more impressed when it ran properly the next morning...
I was impressed.
I was even more impressed when it ran properly the next morning...
Barry
Well Known Member
Early this year I did check the exhaust valves on my O360.
Here in France the local flying club uses a go no go gage.
Basically you need to drop the exhaust pipes so as to see where the exhaust valves go into the cylinders. Remove the rocker cover and then release the valve spring mechanism so that you can slide the valve into the cylinder. The trick is to try and avoid the valve falling into the cylinder. I used a flexible gripper to try and hold on to the end of the exhaust valve. Once the valve is out of the valve guide try the go/no go gage. If the go end of the gage will no go due to the guide having a deposit on it ream out the guide with a half inch reamer. Then slide the valve back into the guide and reassemble. If as happened to me the valve drops into the cylinder you can eventually fish it out with a magnet. After 700 hours on my Lyc O360 I had two valves guides that needed reaming out. I have noticed the engine to be smoother since doing the valve guide work.
Hope this helps
Barry RV6a F-PRVM grounded for 3 months with a broken leg!!
Here in France the local flying club uses a go no go gage.
Basically you need to drop the exhaust pipes so as to see where the exhaust valves go into the cylinders. Remove the rocker cover and then release the valve spring mechanism so that you can slide the valve into the cylinder. The trick is to try and avoid the valve falling into the cylinder. I used a flexible gripper to try and hold on to the end of the exhaust valve. Once the valve is out of the valve guide try the go/no go gage. If the go end of the gage will no go due to the guide having a deposit on it ream out the guide with a half inch reamer. Then slide the valve back into the guide and reassemble. If as happened to me the valve drops into the cylinder you can eventually fish it out with a magnet. After 700 hours on my Lyc O360 I had two valves guides that needed reaming out. I have noticed the engine to be smoother since doing the valve guide work.
Hope this helps
Barry RV6a F-PRVM grounded for 3 months with a broken leg!!
Mike S
Senior Curmudgeon
Yep, been there, done that.
Another trick is to just spray the valve stem with penetrating oil ---I like "Kroil"-- and spin it in the guide with a cordless drill. This works for a valve that isnt stuck so bad it needs a hammer to move it. You done even need to push the valve out into the cylinder for this one.
Beware of one "Gotcha" though, I have had the rope tie into a knot inside the cylinder---------if the rope starts to get stubborn on the removal, dont try to force it
------find out what is going on, and maybe you wont have to go ahead and remove the jug for a stinkin' knot, like I did
Another trick is to just spray the valve stem with penetrating oil ---I like "Kroil"-- and spin it in the guide with a cordless drill. This works for a valve that isnt stuck so bad it needs a hammer to move it. You done even need to push the valve out into the cylinder for this one.
Beware of one "Gotcha" though, I have had the rope tie into a knot inside the cylinder---------if the rope starts to get stubborn on the removal, dont try to force it
------find out what is going on, and maybe you wont have to go ahead and remove the jug for a stinkin' knot, like I didOK NEW PROBLEM>>>>
Well..... as John W or Ronnie would say, my offending cylinder's exhaust valve is not even close to being stuck. It is smooth and has very little wobble. So now I'm wondering what causes that cylinder to sputter at first startup of the day....
Plugs look good. I'm lost!
By the way, the rope trick isn't a slam dunk. You have to keep screwing around with it to get it positioned properly to hold the face of the valve. And the SB doesn't make any mention of what to look for. It just says what to do if it's stuck. No comment on how that should be determined.....
I'm assuming a valve that can be pushed in and out very smoothly and spun on it's axis as well as pulled tight against it's seat and then turned and squeaked is about as good as it gets?
Now what's that morning miss???????
Well..... as John W or Ronnie would say, my offending cylinder's exhaust valve is not even close to being stuck. It is smooth and has very little wobble. So now I'm wondering what causes that cylinder to sputter at first startup of the day....
Plugs look good. I'm lost!
By the way, the rope trick isn't a slam dunk. You have to keep screwing around with it to get it positioned properly to hold the face of the valve. And the SB doesn't make any mention of what to look for. It just says what to do if it's stuck. No comment on how that should be determined.....
I'm assuming a valve that can be pushed in and out very smoothly and spun on it's axis as well as pulled tight against it's seat and then turned and squeaked is about as good as it gets?
Now what's that morning miss???????
