Removed Cylinders to Solve Sticky Valve

I've been slowly working on the sticky valve problem.

I removed Cylinder #2, the one with the sticky valve and covered the hole to keep dirt from blowing in around the hangar doors.

I decided to make a new tool for for removing the valve spring keepers.  I tried buying one but didn't like what I found.  Years ago I had modified the handle of my, 7th grade, tack hammer to do the job.  It never worked great but it was my inspiration for this one. I had some 1/4" steel rod, like the hammer handle, so that's what I used.

I cut a piece I thought was long enough, folded it in half and started forming the bends.

The hooked end goes under the rocker arm shaft.

The step down is to push on the center of the spring retainer.

The wide gap is to have room to get the 2 keepers in or out.

With the end hooked under the rocker shaft the tool is pressing on the spring retainer.  To keep the valve from moving as you press down, the valves are resting on the flat top of this wooded block.

The block is made from a piece of 1/2" plywood for the base with a piece of 4x4 screwed to it.  The 4x4 has the corners rounded, to fit in the barrel of the cylinder.  The angles at the top allow the cylinder to set down so the valves are on the top of the wood.  It works real good.  I got the idea from an old training movie.

You press down on the handle to expose the 2 keepers.  I use a good magnet to remove the keepers while pushing on the handle.

I took the new valve and stuck it in the guide from the top to see how far in it went before sticking.  It stopped about 1/4" from the bottom of the guide.  It should have fallen all the way down.  The build up of carbon stopped it.

I didn't want to use a power tool because I didn't want to accidentally make the inside diameter too large and then have to get the guide replaced.  It's a 7/16" diameter hole.

I tried a variety of 1/2" brass and steel brushes.  The brass did nothing.  The steel brushes worked, but very slowly.  I also made a stick of 3/8" dowl to hold Crocus Cloth for final polishing.

The thing that worked best was the small blade on my Swiss Army knife.  Stick the blade in the hole, from the cylinder end, the curve of the blade prevents scratching the wall of the guide.  Use it ase a screaper to scape the carbon as you rotate the cylinder around the blade.  It's still very slow, but better than the wire brush.  I used the brush after scaping with the knife.  It was surprising how much carbon came loose as a fine powder.

I also tried Easy-Off oven cleaner.  It worked well to soften the carbon on the valve stem where you could spray a good coating and let it set over night.  

I used a Q-tip to apply it in the guide but really never got enough to do much.

It might have worked if I could have blocked the end of the guide and filled it with cleaner.

To make sure I removed enough carbon without increasing the hole size, I measured the outside diameter of the valve stem and the inside diameter of the guide.  The book allows 0.0035" to 0.0055" clearance. The stem is easy to measure.  The guide hole rquires a hole gauge, which you adjust to fit the hole, then you measure across the gauge. I had to work from the top of the guide so the longer hole gauge was able to reach the bottom.  The anvils are spring loaded.  When you have it where you want you twist the handle to lock it, then pull it out and measure it, Very tedious.  There was so little wear that the best I could do was get the clearnace to 0.0035".  The valve really moves freely when you have that clearance.

To make sure the new valve sealed well I got some valve lapping compound.  The tube came from Advance Auto and the jar from NAPA.  It turns out they are both the same stuff.  The tube, 80036, was about $5and the jar, 39835, was about $8.  Either is probably a lifetime supply.  It's a water based gray paste with silicon carbide grit, from 120 to 220 grit.

Get a dab on your finger and apply it to the sealing surface of the valve.

Carefully reinstall the valve in the guide so you don't wipe off the grit or get it on anything but the valve seat.

You are going to oscillate the valve against the seat to lap the 2 to the same angle for a tight fit.  They make a stick with a suction cup on the end to do this but it takes a very long one to reach down into the cylinder.  Instead I used the drill chuck from the ShopSmith to grip the end of the valve stem and pull the valve against the seat vs pushing it with a stick.

The lapping process is simple.  With the valve tight to the seat you rotate the valve back and forth about 40 degrees until you feel it moving smoothly.  You really feel the grit at first.  Then move the valve off the seat, rotate 90 dregees and repeat.  Keep doing this in sets of 4 90 degree moves until you barely feel the coarse grit.

Clean everything well to be sure no grit is left to get where it shouldn't be, then pressure test the cylinder to assure you have a seal.  Repeat the process if needed until it seals.  They do make lapping compound as fine as 1,000 grit.  I didn't order any.

I didn't want to lubricate everything, put the piston back in and reinstall the cylinder on the motor just to leak ckeck it.  Instead I made up a plate to seal the bottom of the cylinder.  I used some scrap 1/8" steel, some 3/8" nuts and bolts from Tractor Supply, and some 1/8" cork gasket material glued to the steel plate.

Snug the bolts up and it seals, so you can use the cylinder differential pressure tester to slowly apply pressure.  Yea no leak.

There was no logic by which I can believe this was the only cylinder with carbon built up in the exhaust valve guide.  I couldn't in good conscience put this one back on and ignore the others.  Off with the next cylinder and repeat the process.

When putting cylinder 4 back on I couldn't get the hydraulic valve lifter to compress to get the shaft back through the rocker arm.  I called my friend Caleb Glick, who has since died and will be sorely missed.  He explained that the check ball in the plunger was stuck and that the plunger can be removed with a magnet, then cleaned.  This involved removing the casting which has tabs cast in it to prevent the plunger falling out of the lifter.

Once the casting was off the plungers are easy to remove with a magnet.

The long piece on the left has the check valve in it.  It lets oil flow through the lifter and up the push rod to lubricate the rocker and valve. I blew Brake kleaner in the small tube untill it was cleary open, then I oiled everything and put it all back together.

I found one of the lifters on cylinder 2 was not compressing so I took the cylinder back off and cleaned the check valve on it.  All 8 lifters are now working fine.

Cylinders 2 and 4 are on, and 1 and 3 are off to clean the valve guides.

Cylinder 3 was easy, but I replaced the valve on cylinder 1.  Even though it hadn't stuck it was worse than cylinder 2.  It took more force to pound out the valve.

After the first lapping the valve had some leakage.  I blued the sealing surface on the new and old valves, installed them with no compound, and only oscillated it a few degrees.  There was a small low spot on the seat which needed some more lapping.

 

I also found that the new valve had some chatter in the original grinding.  The 3 arrows point at high spots you gan see in the bluing.  Chatter basically leaves little flat segments with corners between them.  The little high spots, corners, cause leakage until the lapping smooths them down.

I could hear a very slight leak even though the pressure was good.  I put a few drops of soap solution on top of the valve.  You can see the bubbles all the way around the valve at 10 psi.  More lapping.

With the valves working the cylinders are back on and pressure checked just to be sure, all 4 were good.

One side at a time the exhast and baffles went back on and everything was reconnected and safetied.

When I finished today I just need to clean up the mess, do one more inspection, and reinstall the cowl sheet metal, we're getting there.

Airport Finished - Sticky Exhaust Valve - No Flying

 They finished the new runway a couple weeks ahead of schedule.  It's flat end to end. You can almost read the numbers from the other end. 

Looking SW down Rwy 5 you can see the grass where the taxiway was.  Because it sets so much lower than the runway all taxiing may have to be on the runway.  That will really limit how many planes can be in  the pattern at one time to about 2 or 3.  We'll find out in the spring when we can drive on it.

Hangars, looking west.

No more down hill to the north.

The town had the official ribbon cutting November 16th.  Well Done.

With the runway open I needed to finish my Condition (Annual) Inspection.  Since it ran out during the closure I couldn't go flying to warm up the engine before checking the compression.  I decided to check the engine compression cold, then recheck it after a flight.  The compression check was my last task.  All the valves looked good with the borescope and cylinders 1,3 and 4 all had good compression.  Cylinder 2 had no compression.  The leak is through the exhaust valve.  The motor runs full rich, no mixture control, and I've had high cylinder head temps, so carbon buildup on the valve stem and guide was suspected.

Cylinder 1 Exhaust.  The oil stain is from oil I sprayed in the cylinders to help prevent rust while it sat.

Cylinder 2 Exhaust

Cylinder 3 Exhaust

Cylinder 4 Exhaust

Caleb Glick convinced me to clean the valve stem and guide without removing the cylinder.  My first step was to remove the rocker and valve springs.  To hold the valve closed while I compressed the spring, I bought a 50 ft. roll of 1/4" nylon rope.  I fed 25 feet into the cylinder with the piston down, then rotated the piston to top center, compressing the rope against the valve.  It took that much rope to get the rope tight, without the piston going past top center. With the springs removed I clamped a drill chuck on the end of the valve stem.  I was able to pull the valve tight and compression checked good.  It looks like we're on the right track.

I tied a length of flat rib stitch cord to the groove in the stem where the little keepers for the spring retainer sit.

Then, with the piston at bottom, I used a brass rod to gently tap the valve into the chamber.

I used a piece of safety wire to fish out the cord and move the end of the valve stem to the spark plug hole.

There is some soot build up on the lower end so I cleaned it up and polished it with crocus cloth.

I used a round wire brush to clean the valve guide.

The valve stem and guide were oiled and the cord was then used to pull the valve stem back through the guide.  I used a curved end rib stitch needle to lift the valve end to get it aligned with the guide.

The rope was used to hold the valve while I compressed the springs to put the springs back together.

I should have checked the compression first.  It's better but I still have a leak through the valve.  After some experimenting, I've decided to remove the cylinder and replace the valve.  I've ordered parts from Fresno Air Parts.  They should be here in a couple days.

I have removed the grills from the Nose Cowl so when this is back together we'll see if that helps the temperature problem.

Nose Cowl Inlet Discoveries

 I'm still trying to solve my high cylinder head temperature problem.  Cylinder cooling depends on the size of the inlet openings, to get good inlet pressure.  Then the baffles have to assure the air coming in goes through the cooling fins, with no leaks.  The rate of airflow across the cylinders depends on the outlet size to create a pressure drop from above the cylinders to below them.

I started with the assumption that the Taylorcraft nose cowl openings were obviously larger than the old cowl so it should work fine.  I've worn myself out looking for leaks and playing with the outlet opening and skirt.  I've made some improvements but never solved the problem.

The other day I had the bright idea that maybe the grills on the Taylorcraft cowl were blocking the airflow.  After all the Taylorcraft used a 65 HP motor and mine's 85 HP.  I decided to remove them and see if it improves the flow, when the airport reopens in November.  This required removing the nose cowl to get them out.

While I was removing the nose cowl I decided to position the old nose cowl so I could visually compare them (I don't throw things away until I'm sure I won't ever want them).  I think the current term is OMG.  Houston, we have a problem.  The useful area of the Taylorcraft openings is clearly smaller than the old cowl inlets.

Time to lay this out in CAD to learn some truth.

I used the prop opening to align the 2 cowls in TurboCAD.

The Yellow line is the old Inlet.  The one thing you see is that it is positioned to focus air on the cylinder head.

The Magenta line is the top of the front baffle.  The best airflow is above that line.  Most of the Taylorcraft inlet is below that line.

Yes the grill is blocking airflow to my cylinders.

Here are the numbers:

Old  Inlet                                  T'craft Inlet

33.9 sq in                                  58.6 sq in without Grill  (much bigger)

                                                  39.2 sq in with Grill       ( not much bigger)

Above Line

26.1 sq in                                   23.6 sq in without Grill (10% smaller)

                                                   15.5 sq in with Grill      (41% smaller) OUCH!!!

I've removed the grills and redone the skirt without the lip.

They're ahead of schedule on the runway so I may wait to recover the fuselage until after the runway is done so I can see if this is the answer.

They have the base gravel down and this runway really looks good.

The first picture is looking SW and the second looking NE.

Very flat, slightly downhill to the NE