Getting The Injection System Done And Making It Run.
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Go Back Home.
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28 May 2018:
Well, in response to a numerous request, here is a video of the naphtha combustion test I did this morning.
 Here's the link:
In case you're interested, the motor is running the engine at about 600 RPM.

Now, while motoring the engine, I will stufy the Lombardini injection pump sent to me by Doc.  I hope I can use some of it on this engine because it has the helix on the plunger to control the amount of fuel delivered.  This would be the easiest way to get the job done.  I will still have to come=up with the injector.

The Lombardini injector on the left, pump on right..
I'd like to use the injector, too but it's way too big to fit on this little engine.
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29 May 2018:
I took the Lambordini pump apart and think that I can make my own housing so it will be small enough to mount on the engine.
 
            Disassembled pump.                                                          The rusted spring in the outlet valve.

Here is a drawing of the important parts of the pump.
As you can see in the right-hand photo above, the pump got some water into it's outlet and rusted the delivery valve spring in two.  I'll see if I can get a replacement.  If anyone out there has one, it would be nice to have it.  I think the engine is a Model 6LD435 or 6LD435A.  I looked in the injection system specifications and the injector cracking pressure should be set between 2,755 PSI and 3,055 PSI, a lot higher than I plan for my injector so the internal pump parts should work fine on my engine.  Delivery volume could be too high but I think I can compensate by setting the stroke of the pump shorter or simply changing the amount the plunger can turn between full power and cut-off.   
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3 June 2018:
I thought I'd report on progress on the pump.  I've been working on CAD while doing yard work, etc. and think I am close to turning good metal into chips and scrap.

Design for the new pump.
I will mount the pump as an outrigger at the end of the camshaft.  I sure hope I get this right because it is a pain to re-engineer it.  With a little more design work to do, I will soon back in the shop.
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5 June 2018:
Here is the mount for the injection pump.

Injection pump mounting bracket.

The mount was made from a piece of 2" X 4" X 1/4" steel tube.  Whittling it to shape took a while.
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6 June 2018:
The pump housing is made and I think it will work.

The pump housing minus guts for now.
Tomorrow, time permitting, I will get the top cap for the pump done so I can assemble it.  When the cam follower is done, I can make the final measurements for the cam.  The linkage from the governor is going to be a bit on the Mickey Mouse side but it should work.  It will be a bit springy but that ought to allow the lever on the pump to be shoved to the cut-off position to stop the engine.  I'm interested to see how much the pump leaks through the plunger/barrel clearance.  There are no seals on this pump and Lombardini says that, if the engine oil level rises from Diesel fuel leakage, it's time to replace the pump.
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7 June 2018:
The top of the injector is almost done.

Injector top being test fitted.
Since I didn't have any L-10 steel of the right size and didn't want to turn down a really BIG round, I resorted to brass.  Expensive, but easy to machine.  What's left on it is to mill four flats for a 3/4" wrench.
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8 June 2018:
I really wanted to put a 7/8" hex on the top of the pump but don't have a collet that fits into a hex housing to do just that.  Shazam!  I came up with a neat way to get the job done.
 
Making the hex on the valve housing.

Since the outlet fitting has a nice hex on it, I decided to use it as an indexing tool.  As you can see, I used a 6-point semi box end wrench to locate the housing, making sure to take the slop out of the wrench to fitting fit.  The major diameter is 1" so, for the first three flats, I took off 0.0625".  Then, using the first three flats for references, I then set the mill to remove 0.125" from the remaining three flats.  I must say this was a brilliant move on my part.  A close inspection of the "nut" shows no difference in the slight O.D. between the ends of the flats.

I'd rather be lucky than good!

Here's the pump ready for the fiddly bits.
I've got some filing and fitting to do to get the fuel control lever to completely cut-off the fuel.  There was an eccentric in the original housing that worked on the barrel, rotating it a little each way and I think it was used during assembly to set the cut off.  When I built my housing, I used a simple 4-40 screw to locate the barrel.  What I have to do now is to file a little off of the bracket so the lever will move far enough toward cutoff to stop fuel output.

Oh, yes, that IS a screw starter between the camshaft and the follower.  It is there as a temporary prop to keep the follower from falling off.  Note that I've added a bleeder screw just this side of the fuel inlet barb.

When I assembled the pump this time, I left the delivery valve poppet out so I can determine the start of fueling.  Once I get the cutoff lever filed to where I want it, I will attach a fuel tank to the pump, bleed it and measure the actual position of the follower at the start of delivery.  Then I will determine the maximum fuel point and measure the follower position again.  These measurements will give me the information I will need to make the cam that drives the pump.  Now, since I've never done this before, I may find some "aw-shoots" but that's part of the learnin' process.
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9 June 2018:
The measurements are done and the cam will have a rise of 0.060 for full fueling.

Here's the setup for measuring start of delivery and max fuel.
The pump cam will have a major diameter (end of delivery) of 1.990" and a minor diameter (start of delivery) of 1.870".  This allows about 0.020" extra for overtravel.  It's designed to have the follower a few degrees into the ramp before fueling starts.

I've also substituted a lighter plunger spring for the stock one because I need to minimize load on the un-hardened cam.  If it's too weak, engine speed will be limited.

The cam should be done tomorrow and I will then motor the engine to make sure all works.  I have to keep in mind that this pump may not work due to the fact that it is for a the larger Lombardini 6LD435 engine that has a displacement of 26.6 cubic inches as opposed to the 2.48 cubic inch volume of my engine.  This makes the pump about 10.7 times too big.  Because of this, I have some doubts that delivery can be throttled back enough.  We'll see.

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10 June 2018:
Got the cam made but something went wrong with the dimensions.  I put it all together and the pump doesn't pump.  I think the pump stroke is wrong.  I'll take some time off of the project and try to winkle out what's the matter. 
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12 June 2018:
Back on the job.  I got the pump figured out.  I had the pump plunger too high by about 0.050".  Once I lowered it by that amount, it started pumping just fine.

Then, I started-in again on the injector.  So far, I've still got a lot of dribbles and side squirts.  Changed the poppet angle to around 15 degrees and am now in the process of getting the valve lapped-in again.  Tomorrow, we may see a spray but I wouldn't hold my breath.  Got some fiddling with springs to do.

The latest iteration of the injector.
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15 June 2018:
Well, today, I got the injector poppet lapped until it made a "sort-of" acceptable spray.
 
            The injector tip.                                                           The injector installed on the engine.
I got it all on and decided to give it a spin to see if it would make smoke.  I got the camera going and motored it then increased the fuel.  Nothing happened except that the gasket on the injector to head joint blew.  Then the intake valve stuck from interference with the injector so off came the head for a bit of a re-work.

I was using the body from the original test injector and hoped that it would seal on the threads.  Not!  Even a gasket didn't help.  I will make a new bottom half of the injector, this time with a flange so I can use a copper washer.  Also, the previous injector was about 0.100" short.

Since the engine didn't fire, I deleted the video.   I'll try again when I get things fixed.
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17 June 2018:
Back at it today, I did some CAD on the injector.

The new injector design.
This design uses the top of the previous injector, modified for length and a different fuel line fitting arrangement.  That and the copper gasket washers are what I got done aside from the CAD today.  Not shown in the drawing is the spring that holds the poppet shut.

I've decided to go with a 10 degree seat and 15 degree valve face on the poppet.  This will make it easier to lap it to fit.  I may try to make the head of the valve by heating it and hammering a rough shape, then machining the face.  The previous poppet was two piece, peened into place on the stem.  That was really difficult to make because it is so small.  The body and valve are all that is left to make.

The injector shaft is threaded 12-24 and screws into the head with a copper sealing washer.

A follower of this page says that I should be careful to not let the injector get trapped in the head by carbon build-up in the threads.  After it is debugged, I will apply some anti-seize compound to the threads.  That should help the situation.  I've had that problem with The Homebrew Hvid explosion cup getting stuck due to carbon build-up.
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18 June 2018:
FIRST SMOKE!  
Nothing too much to brag about but the engine did make smoke (lots of it!) and sounded like it was running although I didn't take it off the belt.
   
    The latest injector.                                                                            Making smoke!
As you can see, it made smoke and stunk-up the shop.  It would only run with the fuel almost all the way on and didn't make enough power for me to try taking it off the belt.  Also, it appeared to blow a lot of unburned fuel past the rings, an indication of poor spray pattern.
Who IS that old bald headed guy in the flick??

Along with finishing the injector, I raised the compression to the maximum (without making more shims).  I will re-visit the injector tomorrow.  Once it is running fairly well, I will hook up the governor and make a cooling system.  I think I've got a small piece of air conditioner condenser left up in the attic to make it out of.
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19 June 2018:
I found one reason the engine didn't run well and smoked.

Poppet pushed back into it's guide.
As you can see, the poppet had been blown back into the bore of the injector.  No wonder it was flakey.  The reason this happened is that I made the previous poppet head too small.  In any case, I didn't like the way heating and peening a head on the drill rod worked, distorting it at the head end.  My solution was to use my Dremel toolpost grinder to turn the 0.069" drill rod down to 0.048" at the end then, using some 0.125" drill rod, making the head, drilling it to just fit over the turned end of the stem.  The head was slipped over the turned area and the stem was peened to hold the head firmly in place.
   
        Head on stem ready for peening.                               Peening the head of the injector poppet                                  Grinding the 15 degree face on the poppet.
Note the home-made collet to hold the poppet stem in while working on it.  Not seen is the split that is sawn parallel to the bore of the "collet" to allow it to clamp the drill rod in place.  Using the Dremel as a toolpost grinder is all right except that it doesn't give a really fine finish on small parts, making it necessary to spend the better part of the morning lapping it to fit and seal in the injector body.

When the poppet was finished, shims were added to the spring to get the cracking pressure up to around 1,200 PSI.  Although nothing to write home about, the spray was finer.  After putting the injector back on the engine, the timing was retarded to about 10 degrees ATDC and it was motored and, using the heat gun for a minute or so, it started firing.  Not wanting to run it long enough to overheat, I did find that it runs better and, at the end of the short run, I flipped the belt off and the engine continued to run for a few seconds but finally slowed and stopped.  I think that with an hour or so of constant run time, the compression will rise and it will run better.  The goal is to be able to crank start it and have it run reliably.  

Core for the radiator.
I went up to the attic and found the remainder of the air conditioner condenser coil.  I will use it for a radiator which is next on my list.  Once that is done, I will hook-up the governor, make an adapter for the outside exhaust and will then be able to run it without stinking up the shop too much.  It is hot and humid here in the Panhandle of Florida and, yesterday, I turned off the air conditioner, raised windows and ran a fan to clear out the smoke.  During that short time, the ways on the lathe and table on the mill got a haze of rust from condensation.  Not good!

It will probably be a few days until I post again.  Maybe by that time, I will have it running with the outside exhaust and will make another video of it as it progresses to a show ready engine.
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22 June 2018:
Today, I finished the radiator and started on the skids.
 
Radiator.
Tomorrow, I will finish the skids and give them a coat of paint then I will rework the injector poppet.  I think my homemade "collet" got the poppet a thousandth or so off center and, when I lapped it, there is a groove around about half of it.  That is probably what is making it run erratically.
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23 June 2018:
Making progress.

Skids and radiator done.
I'd rather be lucky than good.   After hooking up the plumbing and filling the radiator, I find that I have no leaks after a couple of hours.  I will confess that the soldering job wasn't perfect because when I tested it in the sink, there was one little "spritzer" in a corner of the top tank.  A touch of the soldering iron fixed that.

Before I attempt to run it any more, I'm going to give the injector poppet another workover.  When looking at the lapped face of the poppet, I can see a little groove on one side and no groove on the other.  In thinking about it, I believe my "collet" is the cause of a little runout when I faced the valve.  I think I'll try to chuck it in the mill and use a stone mounted in the vise at a 15 degree angle to touch up the face.  This means that I'll have to re-lap it but I think the slight groove (as near as I can tell, it's about 0.001" deep) may be causing an uneven spray pattern.

I won't know if I can improve the face until I chuck it up and indicate the stem.  If the chuck has a little runout, I may be able to rotate the stem a little and minimize it.  As it is, I'm working past the limit of "teensy" I can reliably do.
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24 June 2018:
Well, I worked over the injector poppet on the mill.
   
Checking runout of stem.                                               Setting angle of stone.                                                   Truing up the poppet face.
I put the poppet in the mill chuck and trued it up by bending the stem so there was no runout.  Then, I put a small Arkansas stone in the mill vise and set it to grind a 15 degree face on the poppet.  Working the poppet back and forth over the stone while engaging it about 0.0004".  The stem seemed to be better but after a couple of hours, I decided that it was good enough.  Not!
 
Blowby mess.                                                                              Radiator leak.
After making an exhaust adapter (that leaks!), I spent a couple of hours stinking up the shop.  I set the injection timing to about TDC and it wouldn't fire regularly even using the heat gun on the intake..  I then set it a little after TDC and it acted like it wanted to run but not quite (still using the heat gun).  I set the timing to about 10 degrees after TDC and, with the heat gun, it made sounds like it wanted to run.  I let it run on the motor with heat until the top radiator tank was pretty warm.  At that point, I set the injection volume to a point where it was only smoking slightly gray, removed the heat and then flipped off the belt.  The engine continued to run but, because it's a Diesel, I had to constantly either adjust the fueling or hold a rag to a flywheel to keep it from overspeeding.

Although it ran on it's own, I'm still unhappy with the amount of white smoke it's making.  It also struggles to accelerate even when enough fuel in injected to make it really smoke.  After the run, I noticed that it was leaking a little compression back through the injector so I will again remove the injector and work on the poppet some more.

As you will notice in the last couple of photos, the radiator is leaking.  I will have to remove it to lift one of the side braces to see where the leak is and fix it.

Something I might try is to lower the compression a little to see if I can get it to fire closer to TDC.  I'm sort of flying blind here but, as with The Homebrew Hvid, there was a lot of fiddly stuff to do and things to learn.
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26 June 2018:
After spending some more quality time working on the injector poppet face and re-working the exhaust system to eliminate the leaks and subsequent stink in my shop, I motored it for a bit and, after finding the sweet spot on the fuel delivery lever, I hooked up the governor and motored it until it was running.  To give it a test, I drained the tank of #2 Diesel fuel and poured in some Jet-A (kerosene).  Motored it a bit more then removed the belt and made the movie before I messed it up.


AND, I did mess it up.  Deciding that I could make it run better by tweaking the fuel delivery, governor springs and the pump timing, I finally succeeded in getting it to where it would not run off the belt.  I'll figure it out tomorrow.

Running on it's own on the governor.
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27 June 2018:
Today, to minimize stinking-up the shop for another day, I moved the engine and stand outside.  It didn't take but a few seconds of motoring with no added heat to get it firing but I couldn't get it to sustain running off the belt.  Since it was HOT and humid outside, I quit after about two hours.

One thing I did ascertain is that it does as well with a compression shim removed so the rings must be breaking-in.

Tomorrow, I will yet again work on the injector.  It is not leaking but I think the running difficulty is caused by a bad spray pattern that is getting worse.  I also intend to make a fuel delivery stop screw to limit the maximum fuel permitted.  Right now, I can increase fueling to the point it quits firing and wet stacks.  It's kinda obvious that would happen because the pump volume is for a much larger displacement engine.
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28 June 2018:
I had a breakthrough of sorts today.  I pulled thje injector and removed the poppet.  Chucked it back in the mill chuck and pushed it around until the stem was running true.  Then, I put the rubber polishing disc on the Dremel and grabbed it in the mill vise.  After setting the angle to 20 degrees, I spun the poppet into the wheel and found that it cuts a lot better than the stones and gives a near mirror finish.  After getting the face as true as my limited facilities allowed, I lapped the poppet in the injector housing using some very, very fine alumina lapping compound.  When I hooked it up to the pump and motored the engine, I was happy to see a nice mist pattern from the tip.

After putting tht injector back on the engine, I made a fuel delivery stop that mounts on the pump and limits the maximum amount of fuel the pump can supply.

Fuel stop.
While fiddling with the fuel stop, I found that the engine had very little compression.  There was excess rocker clearance on the exhaust valve.  When I pulled up on the stem, it reluctantly closed.  After slathering on some oil, I tapped the valve to work it loose.  It appeared to be moving fine so I rolled the whole works outside and motored it.  After some smoking and knocking, it started firing without the aid of heat or naphtha.  After some more motoring, I threw off the belt and it almost stayed running.

A few tweaks to the cam timing and governor, it was running reasonably well without a lot of smoke.  The fuel stop was set to where the engine didn't wet satck and it was allowed to run.  After about a half hour, it "sorried out" by slowing down and smoking more and more.  When it stopped, I checked and, sure enough, the exhaust valve was sticking again.  More oil and tapping and it ran for another half hour before sorrying out again.  This time, the valve was working fine but was not seating.  Tomorrow, I will pull the head and see what gives there.
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30 June 2018:
For the last couple of days, I've been chasing minor stuff.  Today, I pulled the head and found that the exhaust valve had a carbon spot on it's face.  A little light lapping with very fine alumina cleaned it up fine so I figured it was ready to go.  Put it all back together using a stiffer exhaust spring and, after using the heat gun it started and ran nicely, better once it warmed-up.  Today, it hardly smoked at all and there was not a drop of slobber from the exhaust.  After about an hour, it started smoking and sorried out again. Tried letting the engine inhale some Marvel Mystery Oil and it came back and ran all right for a few more minutes before doing the same thing.  Low compression!

Tomorrow, the head comes off again to try to figure out what the problem is.  What I may do is chuck the valve in the lathe and turn it at angles that narrow the seating face.  Then, I will lap it again and put it all back together.  Since the cams aren't hardened, I may put the weaker spring back on, especially since the stronger one didn't seem to alleviate the problem.  The theory du jour is that the wider seating face allows carbon to accumulate until it props the valve open just enough for compression to be bled-off.

I may put the compression shim back in.  That's the one I took out a few days ago.  Maybe it will be easier to cold start.
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2 July 2018:
I reworked the face of the exhaust valve.  I turned it to about 40 degrees.  The seat is about 45 degrees.  Then I lapped it and got a nice pattern.  Yesterday, I ran it for about 45 minutes and it was doing well, hardly smoking at all, running at about 600 RPM.  This afternoon I dragged it out and ran it for about another hour or so then it sorried-out again.  No compression.  Snapping the exhaust valve to it's seat makes the engine regain some of it's compression but I'll have to pull the head again and lap the soot off of the seat.

All this is in spite of putting the compression shim back in,and running about 10% Marvel Mystery Oil with 10% naphtha in the Jet-A fuel.
    
Tomorrow, I may reface the exhaust valve to about 35 degrees to see if that will make it cut through the carbon better.  If I thought I could come up with a rotator for that small valve, I'd consider trying it but that would be a bit on the teensy side for me to successfully make.
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5 July 2018:
After another hour or so, it quit again.  Same problem.  Although the engine was running very well with virtually no smoke, it eventually started smoking and slowed to a stop.  It acted as if it was binding and laboring to stay running but, immediately after it stopped, it still turned easily but had little compression.  After taking a day or two off of the project, I will pull the head yet once more and see if the valve seat looks the same.  If so, a decision will have to be made whether to make a new valve with a cast iron head to replace the steel one that is presently giving trouble.

In the meantime, I may work on the fuel lift pump and day tank.
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8 July 2018:
And once again, the exhaust valve was refaced and reground.  The seat was perfect, yet, after about 30 minutes running, it sorried out again.  A thought occurred and that is the valve may be stressed and the heat is warping it.  Maybe I should take a torch to it, heating it to a very dull red and letting it cool slowly then facing it once more and lapping it to see if it will work better.

The good news is that it only took a little heat to get it firing.  The rings must be breaking in.
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10 July 2018:
Back at it today.  First thing I did was to roll it outside and see if it would run after quitting the last time I ran it.  It did start easily with a minimum of heat and ran fine for about 15 minutes before sorrying-out.

I rolled it back in, pulled the head and removed the valves.  The exhaust was again sooted-up.  Some modifications to them was done.
 
Unmodified valve on top, modified valve on bottom.
The valves are actually about the same size but the close view makes them look different.  What I did was to chuck them up in the lathe and turn the bottoms of the heads and stems.  This would let them dissipate heat faster and breathe easier.  Then they were heated to a dull red and allowed to cool slowly to relieve any possible stresses.  While I was at it, I enlarged the intake and exhaust ports as much as I dared.  A bit more lapping and the whole thing was put abck together.

When I ran it, It went for about an hour and a half before it quit.  Toward the middle of the run, the governor started hunting a little, indicating to me that the engine was loosening up as it's parts became better acquainted.

I'll let it "rest" for a day or so and then, without doing anything to it, see if it will run and, if so, for how long.

If all else fails, I guess I can remove and strip the head and try to get it hot enough to relieve any stress that may be in it.

I'm also thinking about making the starting handle, fuel lift pump and day tank using the Lukenheimer oiler jar that was given to me at the Zolfo Springs show this year.
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18 July 2018:
It's been over a week and I haven't done much to the engine except get the day tank made and a start on the fuel lift pump.  I haven't goten to pulling the head and piston yet.

And, yes.  I had to lean one pushrodover to clear the bulb.
 In spite of my best efforts, I got the Lunkenheimer bulb too close to the exhaust pushrod and had to bend the rocker a little to get it to move freely.  That won't do so I may mill out a slot for the fuel line to the injection pump, make an offset base plate  and shift the whole works over toward the injection pump about a quarter inch.

The tallest of the standpipes is for the fuel to enter from the lift pump, which will be mounted on the right-hand side of the aluminum stand.  The shorter standpipe is the one to allow excess fuel to drain back to the tank through the tubing on ;the side facing the camera.  The outlet standpipe is very short and it's outlet is at the side opposite of the camera and goes to the fuel inlet on the right-hand side of the injection pump.
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19 July 2018:
I took the day tank assembly off and made modifications to move it away from the pushrods.  Everything looks copacetic now.
 
Here is the re-located day tank and the partially complete llift pump
Of course, the Law of Unintended Consequences reared it's ugly head.  The actuation of the piston of the lift pump is to be off of the exhaust lifter.  I had it all designed (but not built!).  Now, it needs a re-design due to the relocation of the pump on the day tank assembly.

Soon, I hope to get a fuel tank made and hooked up so I can see if the lift pump works.  Once this is done, I have to do the valves and check out the wrist pin bushing.
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21 July 2018:
I made up a fuel tank from a piece of brass pipe with a couple of 0.015" thick brass ends.

And a fine fuel tank it is.
The lift pump is finished and working.  the plunger is a 1-1/2" piece of 1/8" drill rod (silver steel) with a 1/4" foot pressed on.  The foot acts as the return spring mount.  The seal that I tried and, so far is working fine consists of a 0.200 long piece of 1/4" diameter PTFE (Teflon) that has been drilled so it is a slight push fit over the pump plunger.  The top end of the Teflon piece is chamfered at about 45 degrees and fits into a countersink at the entrance to the pump bore.  The spring presses the Teflon chamfer into the countersink to allow it to squeeze slightly over the plunger.
 
Fuel; tank, lift pump and day tank all hooked up and working.                                       Lift pump, plunger and seal.                
The piece that fits over the exhaust lifter and goes over to the lift pump plunger was one of those cut-and-try exercises.  So far, it is also working fine.

It took a bit of motoring to get the pump to prime then work out all the air in the lines but it filled the day tank and kept a little ahead of the injector pump going full tilt.      

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24 July 2018:
After pulling the head, I pulled the piston and found that it was really, really clagged-up.  It was so bad, all I wanted to do was to dump it into the solvent.  Too black and gooey to risk contaminating my camera.  Trust me, it was bad.  The top two rings were almost stuck and the grooves had filled-in behind the rings to the point I had trouble getting the piston out.

After cleaning it all up, I checked the wrist pin and found the bushing to be loose.  I don't know exactly why it loosened up because it was totally covered with oily slime.  Looking in my bushing box, I found another bushing so I pressed the old one out and replaced it.  This time, instead of reaming it, I used the old wrist pin as a mandrel to lap the new bushing to fit a new wrist pin (a 1/4" hardened, ground and polished dowel pin).  After reassembling the piston and rod, I turned my attention to the head.

The heat treating department here at Hoyt-Clagwell got a visited and gave the head the hots.  I don't know just how hot it got but it was just past blue using my mapp and proplane torches.  I let it cool slowly.

The head after stress relieving treatment.
When cool, I lapped the valves and found that the head had moved a bit from the stress relief.   It took a while to get the lapping done.  I put it all back together, rolled it outside and, after an injection timing adjustment (set to deliver fuel at just after T.D.C.), with a minute of heat, it decided to run.
 
                  Running fine just after taking it off of the heat gun.            If you look carefully, you wills see the fuel squirting from the supply pipe.
I got out my lawn chair and watched it run for about an hour.  Just as I was thinking it was near to prime time,.....................

Just as it was falling on it's face.
..........it suddenly started smoking and fell on it's face.  After it quit, I checked and once again it is very low on compression.  At this point I'm about at a loss as to what to do to fix the problem.  After pulling the head once more, I'm sure I'll find that the exhaust valve face is clagged-up again.   After about a half hour, I added a half ounce of Marvel Mystery Oil to try to keep the clag from building up.  Now, I don't know if the Marvel Mystery Oil didn't have time to stop the clagging or caused it to happen.

I may try changing the valve face angle to something like 40 degrees instead of the 45 it now is.  This should allow the valve to wedge itself more firmly into the seat.

Oh, well - if it was easy, everybody would be doing it.
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27 July 2018:
I again pulled the head and again lapped the clag off of the exhaust valve face and seat.  While I was at it, I harrowed the sealing face on the valve by about half.  Also, this time,when I put it back together, I used a much stronger spring on the troublesome exhaust valve.  I also left the exhaust pipe off to eliminate as much restriction as I could from the exhaust system.

I checked the injector.  Cracking pressure is about 1,200 PSI and it sprays well, making a fog of atomized fuel.

Rolled it outside and started it.  AGAIN, it fell on it's face after less than an hour of running.  One thing, when it runs well it runs very well.  Here's another video of it running today right before it began smoking and quit.
The fourth video in the series.
As you can see, it wasn't smoking but just a little, not enough to cause the engine to clag badly.   Maybe, since the head is not cooled, fuel boils in the injector.  It would take a LOT of heat to make it boil at 1,200 PSI though.   The next time I run it, I will check the head temperature.
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28 July 2018:
Another frustrating day.  After having thought about it for a while, I decided that it needed to rotate the exhaust valve to keep the face and seat clean.  
 
The valve rotator.
In the photo on the left, you can probably see the small flanged ball bearing (off of a dead hard disk drive) that is fitted into the exhaust spring.  In the same photo, the piece below it and to the left is the new retainer.  It is turned upside down from it's normal position.  There is a diameter turned that contacts the inner race of the bearing so it will turn with the valve and retainer.  The music wire piece is a sort of primitive ratchet that makes the retainer turn as the valve opens.  After adding another wire piece (not shown) that adds a little friction to the retainer so it doesn't turn back, it works well.  With valve spring pressure on the keeper, there is just enough friction to make the valve follow the retainer.  In operation, the valve turns about ten times a minute.

I thought this would do the trick but again, after about 45 minutes of running nicely, it started smoking and sorried-out once more.  It will be interesting to see what the sealing surfaces look like.

About that time, I noticed that the lift pump had quit so there is another thing to take care of tomorrow.
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30 July 2018:
Yesterday, once more reworked the exhaust valve which was not warped.  Both the valve and seat were only carboned-up.

Just for giggles, I shimmed the compression ratio as high as the engine design would allow, approximately 25:1.  At this compression ratio, I couldn't get the engine to run off of the belt and it still required heat to start from cold.  Previously I tried 16.1;1 which had the engine running but took a lot of heat to get the fire started.  The best so far was a compression ratio of 
17.8:1 but it still took some heat to get it to fire.  If all else fails, I may try something between 17.8:1 and 25:1 to see if there is a sweet spot in that range.

The reason for poor cold starts could be due to leaking piston rings.  When I had it apart to replace the wrist pin bushing, the rings were wearing evenly but I necessarily disturbed the seating when I removed the piston.  Maybe, if I can get more running hours on it (if I don't wear out the head bolt threads!), the rings will seat.

Once I go back to it, I may try #2 diesel fuel to see it it behaves better as far a clagging-up is concerned.  A last resort will be to buy some of the model airplane diesel fuel, which I understand is sort of a witches' brew that could run cleaner and ignite better.

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1 August 2018:
I got a suggestion from SMOKSTAK the other day that maybe my cam durations are too short.  As designed, the intake is 180 degrees and the exhaust is 200 degrees.  I was given a diesel valve timing chart that shows that the intake duration to be 230 degrees and the exhaust to be 245 degrees.  It also shows the intake valve opening 25 degrees BTDC and the exhaust valve closing 15 degrees ATDC, giving an overlap of 40 degrees.  I've checked and find that I have enough clearance at the 17.8:1 compression ratio to be able to accomodate that kind of overlap without crashing the valves.

At this time, I've designed a new exhaust cam with a duration of 245 degrees.  I will swap the old 200 degree exhaust cam to the intake and discard the 180 degree cam.  This will at least allow the engine to breathe better.  I found that, if I used the cold heat gun blowing into the intake, the engine ran a little better so it may be choked from cam durations and timing.  We'll see.
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22 August 2018:
It's been a while so here is an update.  On Doctor's orders, I am on light duty until I get cut on so not much time has been spent in the shop.

What I have done are a bunch of tweaks.  Most of them were unsuccessful, all having to do with the clagging of the exhaust valve.  Because I couldn't get rid of the heavy smoking, I reworked the injector poppet a few times and finally have it to where it is doing reasonably well.  The cracking pressure is only about 1,000 P.S.I. and that's as high as I can get it due to not having a heavier spring and a means to compress it.

I made a couple of iterations of an exhaust valve rotator.  All of them broke after some run time and they didn't seem to improve the clagging problem.  

Because of this, I decided to narrow the exhaust valve sealing area by grinding a 30 degree face on one side of the 45 degree sealing face and a 60 degree face on the other side.  The sealing face is now narrowed from about 0.060" to about 0.020".  Today, I ran it for about a half hour and it sorried out again.  I changed to a stiffer valve spring, tapped the valve stem to cut through the carbon and it ran for over an hour before I shut it down.  

There are still some injection timing tweaks to do to try to eliminate the now faint smoke, although the cracking pressure should also be raised to about 1,500 P.S.I.  I really don't have a good way to check the timing so I am moving the injection cam one way and the other, going for maximum happiness.

Right now, I'm running it with a mixture of Jet-A fuel and naphtha.  The ratio is about six to one.  I think the naphtha helps ignition on cold starts.  Eventually, I will try it on #2 Diesel fuel to see if there is any change.

Oh, yes - The water temperature in the top tank of the radiator is about 170F when it stabilizes.  The bottom tank is much cooler so the radiator is doing it's job well.  I may try pinching off the coolant flow to get the top tank temperature up to around 200F and see if that affects the smoking any.

Tomorrow, I may test run it again to see if it will run continuously for a couple of hours.   
Boy!  This is fun!

In case you see me about to do something really stupid and want to warn me, here's my email address
[email protected]
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