The Upside Down Engine

Part Two

Go To Part Three
where we convert the engine from the troublesome
slide valves to the more modern conventional
poppet valves.


This is where we may get the engine to run.  Fixing the valves will probably do it.


7 April 2014:
Last night, I thought that the reason that the valves leaked so badly was because of distortion of the thrust plate.  When I designed it, I made sure it was made of a really stout piece of steel so it wouldn't distort under pressure but what do I know.  To prove the point, today, I made a jack so I could push on the center of the thrust plate to see if that was the problem.  Here's the jack I made:

The Home Made Jack.

This little jack uses a 1/2-20 screw as the jacking mechanism.  The base is a scrap of 1.75" bar stock.  Never throw anything away!

After making the jack, I made a spacer that fit between the manifolds and allowed me to put pressure from the skid to the center of the thrust plate.  Starting with the four hold down (up?) bolts just barely snug, I put pressure on the center of he thrust plate and applied air to the cylinder at TDC on the compression stroke.  It leaked like a sieve with air coming out beside the valves.  I tightened down the hold down (up?) bolts and the leakage didn't change.

There was nothing for it but to take down the valves and see what was the matter.  Here's what I found:
Showing the damaged Teflon seats.
I selected the Teflon (PTFE) because of it's 600 degree F temperature rating.  Looks like it doesn't like fire leaks!  Well, I guess it's back to the 'ol drawin' board.  I just might try making a steel plate to replace the upper Teflon seat, leaving the bottom one there.  Now, I've got to check out the suppliers to see what's available.  I think that some accurate polished 0.062" steel plate would work.


13 April 2014:
I decided to go ahead and make a steel plate to replace the upper Teflon plate.  The material is 0.062" A2 air hardening tool steel.  I had my doubts that I would be able to machine it but it ended-up being very nice to work.
The newupper valve plate.
After cutting the plate until it was a no-slack fit in the depression in the engine head, I used some Timesaver lapping compound to get a preliminary fit of the valves to the plate.  

The spring shown is one of four die springs I'll use for clamping the valve plates together.  The plate will be coated with iron filled epoxy before being assembled.   The epoxy will be allowed to firmly harden before again lapping the valves in place before applying pressure and checking the valve timing.  Will it work?  Who knows.  Stay tuned for the next exciting chapter in the continuing saga of The Upside Down Engine.


15 April 2014:
Progress is being made.  The head has been drilled for oiling the top surface of the valves.  The valve plate has been drilled to match the holes made in the head and slots have been milled to distribute the oil..
Valve plate showing surface that fits against the head.                    Valve plate showing valve side and oil holes/grooves.
The oil holes were drilled using a hand drill (electric).  There was no plan here, just to get a passage from the outside to the top of the valve plate.  After the holes were drilled, one in each side, the valve plate was coated with Dykem.  The plate was held in place in the head and the holes were marked using a piece of wire.  After the plate was removed, holes were drilled in it to meet the oil holes in the head,

Then, the valve plate was turned over so the side that contacts the valves was up.  It was mounted in the mill and an 1/8" end mill was used to cut 0.030" deep slots as shown in the right-hand photo above.The copper line shown in the photos will temporarily be used with an oil can to oil the valves.  If the valve arrangement works out, I will make-up oilers to connect to the lines.

Then, the top surface of the valve plate was super cleaned along with the surface of the head that the valve plate meets-up with and iron filled epoxy was spread on the plate, making sure that there was a good coating around the ports.  The epoxy is supposed to do two things.  It is supposed to bed the valve plate and is also supposed to seal the joint between the valve plate and the head.

When assembling the valve plate, valves and manifold, I used a piece of vinyl to seal between the valves and manifold.  This was so that, if any epoxy oozed out, it wouldn't glue the whole works together.  

Valve plate assembled with new screws and springs with hack helping press the assembly together as epoxy hardens.
While I was at it, I made studs to replace the clamping bolts.  The studs are threaded 1/4-20 and are jam fits in the head.  The other (nut) ends of the studs are threaded 1/4-28 for about 3/4".  The fancy nuts eliminate the need to use a wrench when adjusting the clamping pressure and the fine threads allow fine adjustments.

I'll let the epoxy set-up for a couple of days then will dissamble it, remove the plastic, clean out all the slobbered epoxy and then reassemble it with fine lapping compound.  After hooking up thje linkage, I will motor the engine without the spark plug in place to fully seat the valves against the valve plate.  If I'm lucky, it will then hold compression and run.

When I'm sure it will run, I'll work out a throttle valve for the intake and a linkage to the governor.


17 April 2014:
I disassembled the valves and removed the excess epoxy this morning.  After clearing the oil holes, I lubed it up and put it back together.  When I was reassembling the bellcranks, I found this.

Broken yoke.
I guess the yoke failed due to the high drag of the valve when I was trying to get it to seal.  I've already replaced the other yoke on this bellcrank so I'll make the replacement like it.  I do like the later one piece design better and should have done all of them that way.  As a matter of fact; if I had it to do over, I'd make both bellcranks out of a single piece of steel and eliminate all the welding.  They'd also be more accurate.

When I get the yoke made and back on the bellcrank, I can time the valves and ass if they will seal without further lapping.


18 April 2014:
Spent the day making a new bellcrank.  This time I made it in one piece and used a bronze bushing in the pivot point.

The new intake bellcrank.
After tramming the valves, I applied TimeSaver lapping compound and re-assembled the valves.  After motoring the engine for about 15 minutes, it was quittin' time.  More tomorrow.


19 April 2014:
Well, today, I tried to run the engine.  After fiddling with the "squeeze" on the valves, it made good compression and tried to run.  However, when I advanced the ignition until it was almost pushing the motor, the piston ring blew out.  I've made the executive decision to go ahead and make another piston and buy "store boughten" rings for it.


22 April 2014:
Today, I ordered a set of 40mm X 1.5mm piston rings.  These are replacement rings for a Stihl FS280 chain saw.  40 mm (1.574") is about as close as I can get to the 1.557" bore of the engine.  The rings will be 0.018" oversize. There are two approaches I can take.  One is to simply gap the rings so they will fit the bore with clearance and the other is to mount the rings in a mandrel and turn the diameter to 1.557".

The first option has the downside of the rings not being a perfect match to the cylinder but they should break-in to fit.  The second option has the rings fitting the bore perfectly (it says here in the fine print) but the downside is that a machining screw-up could trash them.  The width of the rings is 0.0591" so, if they don't work, the grooves could be opened up to 0.09375" and custom rings ($$) fitted.  Depending on how I feel about it when the rings come in, I could do either option.


29 April 2014:
This was a good news/bad news day.
 I had ordered the 40mm X 1.5mm rings which are replacement rings for a Stihl FS280, whatever that is.  They came in yesterday.
 Here are the piston rings.
I decided to only resize one ring.  A fixture was made from some 1.5" bar stock.  A diameter, narrower than the ring was turned which allowed the ring to be held clamped in place with a thick washer while almost completely compressed.
The fixture for turning the rings.                                                                    In the lathe.      
                          The resized ring.                                                      Grooved piston with resized ring in top groove.
The ring was turned to a compressed O.D. of 1.557", the size of the bore.  The end gap was fine as-is.  The only thing I didn't like is that the rings are notched for an anti-rotation pin.  The notch is facing up so the pressure side has full contact with the bottom of the groove.  I grooved the piston for two rings and tried the piston with the resized ring in the top groove and the second groove empty.  The piston ring sealed but acted like there was no ring at all, the drag was so little.  Not wanting to have any more ring trouble, I decided to do an experiment.

The second ring was not re-sized.  The gap was filed for about 0.010" gap and it was placed in the second groove.

Resized ring in top groove with 0.018 oversized ring in second groove.
There's slightly more drag now and, after motoring for a while, there was virtually no blowby so I guess that particular challenge has finally been met.

When I hooked up the ignition and started fueling, at the sweet spot in the fuel mixture, the engine would fire but the combustion pressure caused the valves to leak.  I cranked up the tension on the valve block as far as I dared and it was better but there was no joy. The engine, when it fired, would blow past the valves and I could feel the valve block moving every time it did that.  After fiddling with valve block compression for a while with no joy, I noticed a shred of Teflon that had been sheared off by a valve so I quit for the day.

It looks kike the Teflon idea isn't going to work so tomorrow, after doing a post-mortem on it to make sure, I think I'll make a steel thrust plate.  There will be higher friction but less give with the steel but it can stand the heat better than the Teflon.


30 April 2014:
I took the valves apart and found that nothing much was wrong.

Valves with Teflon bottom slider.
I really don't know where the flake of Teflon came from because the slider looked okat to me except that it had some rub marks on it.  Because I didn't want to take the chance that the Teflon was okay, I made a steel replacement for the slider.

Valves with new steel slider.
With the steel slider in place, I re-assembled the valves and am now in the process of lapping them in again by motoring the engine with Time Saver compound working.


4 May 2014:
Today, the engine run under it's own power for the first time!

After several days of intermittent motoring with the spark plug out to lap-in the valves to their new thrust plate, I was motoring it while sitting and talking to a new gearhead friend who was visiting our next door neighbor.  He asked how long I should have to motor it before the valves would seal well enough for it to run.  I said I didn't know but stuck my finger into the spark plug hole and it blew my finger right back out so I decided to screw in the plug to see if the valves still leaked.

With the plug in, the valves leaked just a slight amount so I decided to hook up the ignition and turn on the gas.  After twiddling with the spark timing a bit and getting the mixture set, the valves were leaking smoke so I tightened the thrust springs a little and, when I did that, engine was making sounds like an engine and was "pushing" the motor.  I flipped the belt off and, Voila', we have smoke and noise!
I regulated the speed by changing the ignition timing and skibbered oil all over the moving parts and made a video.  Here it is!
Once I have it running better, I will concoct some kind of throttle control and connect it to the governor.

It's a real relief to have this unusual arrangement run.  That's what it's all about.  Almost as good as White Castle hamburgers!  An I having fun or what??!!


9 May 2014:
Well, after running the engine less than an hour, it started laboring.  After I stopped it, I found that the valves were binding.  In fact, as I turned the engine slowly, they groaned as if they were galled.

Today, I took the valves out and here's what I found.
      Tops of valves (exhaust on top)                                                     Bottoms of valves (intake on top)
As you can see, the valves are making pretty good contact with the pressure plates in the port areas but there is about 0.004" of wear as shown at the end of the sliding contact.  There is also a little galling on the bottom surfaces of the valves in the vicinity of the ports.  I think this is lubrication related so, before abandoning them, I will try drilling oiling holes and milling grooves to see if I can get them to oil better.

If this doesn't work, I'll be forced to change to either bronze (alloy??) or either cast or malleable iron for the valves.  I have corresponded with Wayne Grenning who is an expert in slide valve engines and he says that when he made a new head, pressure plate and valve for one of his Otto patent engine restorations; he made the new head and and pressure plate from cast iron and a 75% tin, 25% copper alloy for the slide valve.  This bronze alloy isn't being made commercially any more and I don't have the funds to have the valves cast of the custom alloy so I will have to go with a common grade of metal.

If I do have to make new valves, I will increase the thickness from the 0.250" they are now to either 0.375" or 0.500".  Either way, I can accomodate the extra thickness by milling out the pressure plate.  In doing this, I can get rid of the 0.0625" wear plate that replaced the Teflon.

By the way, Ron Gerlach added some insight into slide valves and was pleased that I'd given up Teflon in the valve train.  Well, I did have to prove it and I proved that Teflon doesn't work where heat expansion and very hot gases are present.


13 May 2014:
Due to a shop accident on 10 May (three fingers involved and 32 stitches!), work on the project will be on hold for two weeks or more.

DAGNABBIT!  Right after getting back from rhe hospital..


30 May 2014:
Well..........I'M BAAAAAACK!  The Doc has given me permission to go back into the shop as long as I'm careful.  I'm again able to make a fist and can sort of grip stuff but need to build up the strength in that hand.  It looks like the end joint of the pinkie finger is going to have limited motion because of the trashed bone.  I've also got numbness on one side of my third and pinkie fingers so have to be careful of where I put them.  If they get injured, I might not know for a while.

The word to the wise is to be sure to have your hand the heck out of the way of the cooling fan of that electric chainsaw.  I was going to test it before completing the assembly and when I pulled the trigger, the motor torqued and threw the fan end of the motor into my hand.

So much for the boo-hoo's.

Today, I worked on the valves.  While I was laid-up, I got a piece of malleable cast iron for the new valves and some 0.015" thick Neoprene to try to get the demand regulator to work right.

       Valve blank roughed-out                                                    Using slitting saw to separate the valves.
The new valves are being made from a piece of 3/8" (nominal) malleable cast iron.  First, I cut out a piece that was the width of two valves plus a small saw kerf.  Using a shell mill, the iron was made flat and both sides parallel.  The reason I milled the iron before cutting it was to make sure both valves were the same thickness.  All of that went well but I had very little extra material to cut it and have the valves be the proper width for a good fit.

Well, darn!
This necessitated my using a 0.014" thick slitting saw in the mill.  I got all the way through and when the valves separated, the saw disassembled itself.  Then I found that, for the last couple of inches of the cut, the saw had drifted.  The misalignment is what destroyed the blade.  My only theory is that the blade (which I picked-up at the Zolfo Springs flea market) had one side of the set that was dull, making it cut a curved line.  Anyhow, the drift of the saw cut was enough to consign a half a day's work to the scrap pile.  Luckily I had enough material to start over.  This time, I gave myself a lot of extra length and width to be able to use the band saw to separate the valves and have enough left over to clean the valves up.

Tomorrow, I may be able to get the valves assembled and lapped.  I'll let the engine motor over while I swap the diaphragm material from the former 0.062" rubberized fabric to the 0.015 Neoprene.


1 June 2014:
I've gotten several things done in the last couple of days.  While the engine was motoring to see what the valve seat contact pattern would be, I made a throttle butterfly for the mixer.

Throttle parts for mixer.
While I had the mixer apart, I replaced the thick diaphragm with the new 0.015" material.  The jury's out as to whether the thinner diaphragm makes the regulator work like it should.

Before putting the mixer back on, I took the valves out to see what the seating pattern was.
Compression side of valves.                                                                   Pressure plate.        
The compression side of the valves looked good with almost all the bluing worn off in the important areas.  The pressure plate part is not quite so important as it doesn't have to resist pressure.  I applied a thin coat of very fine Time Saver lapping compound to the presure side of the valves and motored them for about an hour before taking it apart and cleaning the remainder of the lapping compound off.          
Governor hook-up.                                                                   Link to throttle.
The governor hookup is presently a crude approximation of what it should be.  I use a small torsion spring to hold the throttle shaft in the open position and a heavier spring between the governor rod and the throttle bellcrank to pull the throttle closed.

I belted up the engine and, after just some motoring to try to dial-in the valves, I decided to take Wayne Grenning's suggestion and ditch the die springs, substituting spacers.  This gives a more positive control of the valve seating pressure.  Again motoring, I turned on the ignition and the fuel and the engine tried to run.  After a little tightening up of the thumbscrews on the pressure plate, the engine began to run strongly.  In fact, it would drive the motor and the only way to keep it from overspeeding was to retard the ignition timing.  I think it's one of those engines that really wants to run!

I piddled with the governor adjustments without a lot of success.  The spring that is connected between the governor rod and the throttle bellcrank is too weak to allow any real governor control.  I think that tomorrow, I will try a solid link instead of the spring.

All in all, the engine ran better than ever and, after about an hour of smoking-up the shop, I shut it down to give it a rest.  Things are looking-up!


2 June 2014:
I made a solid link from the governor arm to the throttle bellcrank and the governor now works although it is a bit sluggish.  It could possibly work better in the future with use and limbering up of the parts.

The engine ran for over two hours today and the valves work better the longer it runs.  I still have issues with the demand regulator.  With the ignition timing advanced to where the engine runs "easy", the governor shuts the throttle enough to cause the regulator to cut-off the gas.  The engine falters until the governor opens the throtle enough for the rebulator to resume feeding gas.  The result is what appears to be the governor hunting.  Now, if I retard the timing a bit, the governor has to hold the throttle open more and the regulator feeds gas steadily and the engine runs steadily as well.  Applying some load to the engine has the same effect.

I've tried starting the engine by pulling over the flywheels but it seems to need a pretty good spin with the electric motor for it to start.  With a good spin, it starts after a couple or three times over compression.  I'll build a starting crank and that should solve that particular problem.

At one point this afternoon, the engine ran for almost an hour without missing a beat.  As soon as I get some more details taken care of, I'll make another video.


6 June 2014:
Other things have kept me from finishing the engine.  Today, though, I took the time to make a starting crank so I don't have to depend on the motor to spin it up.

And a fine starting crank it is!
After I finished the crank, I had time to give it a try and, although I had to spin the engine at a pretty good clip, it did start.  The handle is made from a hunk of Nylon bar I had in the bin.  I'm not too proud of the shape of the handle but it does the job.  

Tomorrow, I'm going to take it outside and run it for a few hours to finish breaking the valves in and see how they hold up.

Yet to do is an oiling system for the valves.  Right now, I just give the oil ports a few drops every so often.  Originally, I thought I'd just make a couple more drip oilers but I may make an oiler like those used on the Otto engines and others.  This type of oiler is just a dish that contains oil.  Above the oil level in the dish, there is a gear reduction driven by the cam shaft that has a little crank and a dipper that picks up a drop of oil every so often and deposits it in a little funnel. I don't see any reason why I can't make one with two little cranks, dippers and funnels to do both valve oil ports.  I'm a-thinkin' on it.


7 June 2014:
While the engine was running in the driveway, I decided to make another video.  It ran about another three hours today.


11 June 2014:
After a pause, I got back into the shop again today.  I checked the wear pattern on the valves and found that they weren't quite seated.  To help remedy this, I applied some extra fine Time Saver lapping compound and motored the engine for an hour or so. The pattern is better now and the engine is running better.  After cleaning up the valves again and putting it all back together, I ran the engine for about four hours and the only thing I need to work on beside the demand regulator/mixer is the adjusting nuts for the valve backing plate.  After a while of running, it gets sorry and I find that one or more of the nuts has worked loose.  Because there is very little pressure on the nuts, they tend to creep loose.  My paln is to try putting some packing or Teflon in the unused spring pocket.  I'll put just enough to take up the excess space and gently squeeze against the stud threads.

I've also started on the Otto-style oiler for the valves.

The beginnings of the valve oiler.
The plan is to make a ratchet wheel that is pushed by a pawl that is connected to the intake valve rod.  I'll probably make the ratchet wheel with about 40 teeth.  Then, using a method I saw on YouTube, I'll use a 1/4-28 tap to make a worm wheel about 1" in diameter which will be driven from a 1/4-28 thread on the ratchet shaft.  This will give a lot of reduction and will occasionally meter a drop of oil to each valve oil hole.


12 June 2014:
Today, I tried out the "worm gear from a threading tap" method of making a worm gear.  It took a while to make the fixture to go in the lathe but, once I got the diameter of the blank figured out for 61 teeth and got everything lined-up, it worked like a champ.
         Making the worm gear.                                                                    The worm gear and the worm blank.
A tap is mounted in the chuck of the lathe and the blank is fed into it and allowed to turn with the tap, making a serviceable worm gear.  I used a 1/4-20 tap to make the gear.  The stock I wanted to use was 1.000" in diameter which came out making the gear have 62.832 teeth.  Since this is not possible, I reduced the tooth count to 60 teeth.  To calculate the diameter of the blank for 60 teeth, figure the radius for the teeth.  20 teeth per inch divided into 60 teeth gives 3.00" circumference.  Dividing this circumference by Pi (3.1415925) gives a diameter of 0.9549".  This is the diameter I turned on the blank.

One thing I learned is that you have to be careful to not make the "teeth" of the gear deeper than the normal thread depth for a tapped hole.  If you go too far, the threads begin to eat themselves.  I saw this right as it started to happen and quit at that point.

The worm and gear with the "dabbers".
Pieces of the old brass valves were used to make the stand for the mechanism.  Some more 1" stock for the crank cheeks for the oil pickup rods finished off this part of the oiler.

After doing some numbers, I have decided to make the ratchet with 18 teeth (20 degrees apart) and the worm ratio is 60:1, giving a total ratio of 1080:1.  The ratchet pawl will be driven off of one of the valves so, if the engine is running at 500 RPM (250 ratchet strokes per minute), 1080 divided by 250 gives about 4.32 minutes per rotation of the pickup rods.  This will make the output one drop in about 4 minutes and 20 seconds.

I again made life hard for myself by not using CAD or sketching the oiler with dimensions.  If I had it to do over, I would have made the input shaft higher so I could raise the mechanism and give myself more room for the pickup rods to dip into the oil.  It should work as it is, though.


14 June 2014:
.........Have you ever had one of those days..........

I've been fiddling with the valve oiler.
The oiler so far.
After several false starts, here's what I've got.  On the photo on the left, the wheels turn counterclockwise.  The hooked pieces are supposed to pull up a drop of oil as they leave the oil bath which goes to just below the copper standpipes.  As the hooked pieces approach the top of their arc, the drop is caught by the little wire which transfers it to the standpipe.  The other end of the standpipe is connected to the tubes that go to each end of the valves.  As shown in the left-hand photo, the drop, which I've manually applied to the hooked piece, is just about to be transferred to the standpipe.

After fully assembling the oiler, I turned it with the lathe.  For some reason, the hooked pieces do not pick up any oil.  I've got to figure out if it's a function of the shape of the end of the pieces or the fact that the pieces angle out of the oil instead of being drawn straight up.  For whatever reason, drops don't form.

Once I've figured out what I'm doing, I'll be done.


17 June 2014:
Well, after all this time of fiddling with the rotating oiler, a couple of days ago, I finally said to Hell with it!  

Yesterday, I started re-working the oiler to what I'd originally thought about using.  It uses a common oil reservoir with a master shut-0ff toggle and a needle valve and indicator for each feed.

New oiler ready for assembly.
         Assembled oiler.                                          Oiler mounted and plumbed-up.
I got fancy with the lid, machining the body and a piece that I removed from the original oiler so they fit together.  Then I made a Lexan top "glass".  Gee, it only took two days to get this done.  Counting the off-and-on work on the other oiler, it took about two weeks.

Tomorrow, I'll whip-up something to put some drag on the valve pressure plate nuts.  They tend to work themselves loose after some running.  After I get that done, I'll sit in the heat and enjoy some stack music!  Sweat is good, isn't it?


20 June 2014:
Yesterday, playing with my video editor, I made another video of the engine running, probably the last of the series.  I did learn that my 'puter is again lagging in the speed category.  I sure hoped I wouldn't need to swap CPU or Motherboard (or both) and add memory but, some of the edits take a minute or more with the CPU running at 100% to do.  Dang!  If it ain't one thing, it's another.
I still have some adjusting to do on the governor.  

The last time I ran the engine, I think the demand regulator was working all right but the only way the engine would run was with both the mixture needle and the demand sensitivity full-on.  The plan is to change the demand valve from a needle valve to a pallet valve.  That way, the demand valve will be either full on or full off and the fuel mixture needle that is ahead of it in the gas stream will control the amount of gas that is metered.

--------------------------------- Later the same day --------------------

Well, I worked on the governor linkage with nothing but a cosmetic inprovement, if that.  I also modified the demand regulator with the same result.  I'll try again tomorrow.


21 June 2014:
Here is a photo of the re-aligned governor rocker.
Previous governor rocker.                                                                    Modified governor rocker.
It's not obvious just what I did to the governor rocker arm unless you look at an earlier shot.  The move required a little creative bending to make the bottom of the rocker align with the throttle rod.  This was necessary due to abandoning the intake valve stroke governing idea that required too much power from the governor and didn't work.  This change didn't make the governor work any better.  I may just leave well enough alone because this engine will just be a running display queen and won't be required to do any work.

Next, I changed the demand regulator pallet valve to one with a smaller orfice.  

Demand regulator pallet valve and seat.
Second time on the demand regulator seems to be the charm.  The pallet valve consists of a disc of rubberized fabric glued to a steel mount. This mount is threaded 6-32 and sandwiches the diaphragm between it and the spring cup.  A very short 6-32 screw holds the works together.

I ran the engine for a while to check out the mods.  It did fine until it warmed up then, while I was fiddling with the ignition timing, governor speed and fuel mixture, the valves mysteriously began to leak.  I'll check this out tomorrow.  It could be that the valve timing has slipped.  This happened once before when the intake eccentric slipped on the shaft.  If this has happened again, I may either add another setscrew or just drill and ream them for taper pins.

When this little engine is in the mood, it will start easily and runs well for as long as I want to run it.  At other times, it is temperamental.  I don't know whether this is simply a trait of slide valve engines or something is changing.  So far, I haven't been able to zero-in on a single root cause.   I do think that once I get it to run well again, I'll just leave it the heck alone and see how it does.


22 June 2014:
What I found out after removing the valves and the thrust plate was that the thrust plate was leaking between itself and the engine head.  When I put it in the last time, I used a thin film of bearing set Loktite to seal it to the head and the Locktite apparently didn't like the heat.

Valve thrust plate showing leakage paths.
As you can see, there are combustion leaks around the ports in the joint between the head and the thrust plate.
Bottom (non-pressure side) of valves.                                                  Top (pressure side) of valves.    
Inspection of the valves shows that they are seating fine and nothing else needs to be done to them.  I checked the valve timing and it was right on the money so the setscrews on the eccentrics are holding.
New "gasket for thrust plate.                                                            Gasket tinned in sealing area.
To try to get a good seal between the head and the thrust plate, I decided to try a thin copper sheet that I very lightly tinned at the critical area to increase the thickness of the "gasket" about 0.0005".  I figure the copper and solder are malleable enough to form to the surfaces of the head and the thrust plate.  

Running the engine, I still have some leakage in this location so, if after running it some more tomorrow it still leaks, I may just take it back apart and simply grind out the ends of the cavity the thrust plate fits in and let the valves seat directly on the head.  The only reason I'm using the thrust plate is to take-up the space the original Teflon thrust sheet was in.  If I do eliminate the thrust plate, that's just one less place for leaks to occur.  Doing this will raise the valves by 0.062" (the thickness of the thrust plate) but that will simply put the valves back in the same plane they were in with the Teflon thrust sheets.

Data plate.
Since the engine is definitely a runner, I went ahead and stamped and mounted the data plate on the engine.  This is the last plate I have and since Jerry Evans of South Africa, who made these plates, has died, I will either have to do without or find someone else to make them.  I've done a lot of etched prototype printed circuit boards in the past so I could get the chemicals and find a way to make negative transparencies and do it myself but the process is messy.


29 June 2014:
After running the engine some more, the valves didn't seat-in any better so I decided to change things so the valves seated directly on the head.  I ass-u-med the surface of the head where the valves were to seat was close to true because I'd milled it flat for the Teflon seal.   After grinding and filing the ends of the valve seat cavity in the head so the valves would seat directly on that surface, the fun began.

I used lapping compund on the top surface of the valves but, no matter what I tried, I couldn't get the valves to quit leaking and they were tighter at the end of their stroke than at the beginning.  
Valve thickness measurements.                                         Flattening them.    
I measured the thickness of each valve at six different places and found that the valves had worn unevenly.  This is probably because of all the different seat arrangements I'd tried, each one of them contributing it's own bit of uneven wear.  I carefully set the valves in the mill and, using a shell mill set to the same height, skimmed the surfaces where they seat in the head.  This got the thicknesses to within .002" of each other.  I'm not sure why they didn't come out closer because I was careful to orient them the same way, tap them down against the parallels and didn't change the quill or knee between the two valves.

Close enough, I guess.
Anyway, I'm now motoring the engine with the spark plug out and going out every hour or so to oil the bearings, apply a little very fine lapping compound and tweak the pressure plate setting.  Tomorrow, I'll see if it's any better.

Go To Part Three
where we convert the engine from the troublesome
slide valves to the more modern conventional
poppet valves.

BOY, This is fun!

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