Lenoiresque, Part Two


On this page, I'm going to place my normal low resolution photos.  They load faster on slow hookups.  The difference is - If you click on the picture, a high resolution copy of the picture will load.  This will allow you to see more detail if you want to.  Hit the "Back" button to go back to the page.  If it's cumbersome or you just don't use it, let me know and I'll remove the feature to save server space.


10 February 2008:

I'm going to revisit the Lenoiresque engine project to see if I can make it run better and produce a little more power.  One suggestion I got from a viewer was to increase the size of the intake port and mixer.  Sounds good to me so I've removed the head and am starting on "fixing" some stuff that was sloppily done before I got the mill.


One thing I've never liked was the way the spark plug sat in the head.  For one thing, it ended up at a slight angle and also, the pocket I "milled" with the drill press was too deep and uneven, necessitating the addition of a washer to keep the piston from hitting the ground electrode of the plug.

I'm still learning the capabilities of my new mill and what I can't do.  One thing shown here is that I can't free-hand mill a circle.  To do that, I'll learn to use my boring tool.


The plan for the spark plug hole is to make an insert to thread into the old location, threaded properly for the plug.  I'm going to make it a light press fit into the stepped hole then insure the plug will stay put by either using JB Weld or threading some small machine screws into the joint between the head and the insert.  Maybe, like a belt and suspenders, I'll do both.


The next thing I'm going to do is re-do the intake valve cage.  As you can see, I've removed the original intake valve cage.  I've still got some thinking to do on this and may try a reed valve now that I can machine a good one.  A reed valve should close faster and maybe keep the backfiring down.  Whether it can stand the heat without distorting is another matter.


.............................some time passes......................


I've been to the shop and have reworked the spark plug.


The photos above show the reworked spark plug hole in the head.  The right hand photo shows the head with the plug in place.


I used the boring bar for my mill to clean up and enlarge the hole where the spark plug goes.  The bottom of the hole is 3/4 inch in diameter and the top of the hole is 1 inch in diameter.  I then turned an aluminum insert to be a 0.001" press fit on both diameters.  


I bored the small I.D. of the insert 1/2 inch for the thread.  I then bored another diameter on the top side of the insert that clears the body of the plug so it sets into the head and just barely sticks out past the piston side of the head (Remember the only clearance between the head and the piston is the thickness of the head gasket).  


I then threaded the small I.D. of the insert for the plug.  I need to get a decent 14mm spark plug tap!  The only thing I have now is a thread chaser for spark plugs and it cuts a rotten thread.  It won't run straight either.  At least the plug fits better and is more square with the head surface than it was. 


I've also decided not to add to the press fit because the major outer diameter of the insert will be clamped to the head by one of the head bolts. 


Next thing to do is to sort out what kind of intake valve to use.  I'll cogitate on it.......



11 February 2008:

Today, I decided to simply go with a larger intake valve and cage.

The new valve cage is made of a 3/4" pipe coupling and a nipple.  First, I threaded the nipple into the coupling.  Then I cut the coupling roughly in half and roughed-in the O.D's.  As I started on the intake valve cage, my first idea was to use the same valve that came out of it.  As I worked on the cage, I decided I'd be better off with a valve that had a longer stem.



Before finishing the cage assembly, I bored the head to get dimensions for a press fit for the cage.  On the right, I'm roughing in the valve seat.



Rooting around in my small engine parts, I found a valve from, I think, a Briggs & Stratton engine.  The stem was too big to suit me so I turned the diameter to just under 0.200".  I would have gone smaller but even with a center, it was trying to crowd away from the tool in the center.  As it was, the center diameter was about 0.003" bigger than the ends, so I dressed it down with a file, getting it within about a half thousandth.  I also thinned out the back of the head for lightness.


On the right, you can see the valve out of the lathe with the old end still on it. 



Next, I made a valve guide out of a 3/4" long piece of brass bar stock then put the works in the mill and used a 1/2" milling cutter to bore the hole for the intake runner.  This came out a bit wonky.  I didn't have enough wall thickness in the cage for enough thread to catch the 1/4" pipe runner well, especially after trimming the inside end of the runner.  It doesn't fit awfully well but with a little help from my friend, JB, it'll do for trial.


On the right, you can see the cage with the valve, spring and retainer in place.



Here it is, ready for the JB Weld treatment.  I may have to diddle with the valve spring but that's part of the fun.


On the right is the combustion side of the head showing the new intake valve.  I'm going to leave the exhaust valve alone for the time being.  The only thing I'll change is to eliminate the exhaust runner, letting it vent straight out of the cage.


Next time, I'll work on a mixer.  Since the engine ran with the previous 1/8" pipe components on the intake, I'll fiddle around with some 1/4" pipe junk.  The flutter choke worked pretty well too, so I think I'll make another one, albeit better than twice as big.



12 February 2008:

Today was mixer day!  I got most of the big parts done.  All that's left is the needle valve assembly and the venturi.


The body of the mixer is made out of a defunct pressure washer pump body.  I cut off a likely piece and trimmed it to leave as little unwanted stuff as possible.



 The picture on the left shows cutting the last of the unneeded stuff off.  I them put the piece in the mill and hogged off most of the remaining unwanted stuff.



On the left, I show the main body of the mixer.  The ugly thing on the left is an air conditioning fitting that's been shortened and a piece soldered on.  I bored what you see on top of the ugly thing and turned the mixer body so I could press the body into the now lovely thing.  This will make up the flutter choke housing.



I took another ugly thing (in this case it was part of a steam radiator bleed valve) and made the flutter valve seat.  On the right, you can see all that's left of the ugly thing after I whittled on it some.



Here's a picture of the head with the epoxied intake runner and the mixer (sans needle valve).  I stil have to drill the the flutter valve housing and tap the flutter valve seat for mounting screws.  It will be a simple matter to make the flutter valve disk and pick out a suitable first-try spring.  Note that I've made an arrangement to adjust the flutter valve spring tension without having to take the seat off.


The venturi is going to be a removable insert that will be accessible after taking the flutter valve seat off.  I'll probably use a set screw in the mixer body to hold it in place.  The needle valve assembly will be soldered where the big hole now is and the venturi will end immediately ahead of the jet.


Ever Onward!


13 February 2008:

Today, the mixer got finished.


The flutter choke disc and spring is done.  On the right photo, I took one of the eccentric followers from the dead pressure washer pump  and made the needle valve housing from it.


I made the needle valve out of an 8-32 machine screw.  The jet ends up midway in the diameter of the air flow from the 0.312" venturi (not shown).  The thingie in the bottom of the right hand photo is a first attempt at a check valve.  It wouldn't seal so I made another one out of brass.


Here you see the mixer body with the needle valve housing ready to be soldered in place.   On the right is the completed mixer along with the new brass body check valve.  


The little fittings are made out of steel 10-32 machine screws.  To make the threads seal like pipe threads, I turned tapers on the ends of the screws then tapped the female threads about four turns using a tapered tap.  The screws were drilled out to #55 drill size (0.052").  The drilling was done in the lathe and was a bit tedious but made a cute little pipe nipple and the fuel line hose barb.


Tomorrow, time permitting, I'll put it all back together, fuel it up and see if it will run any better.


14 February 2008:

Well, today was one of those days.  Since the shop was a mess, I cleaned up the joint some.  Then as I was assembling the valves, I found that my new intake valve was not seating properly and burned a couple of hours getting it lapped and sealing right.  


After putting the head back on and hooking up the ignition, I had a heck of a time getting it to run at all.  When it did run, it would only occasionally hit two licks in a row.  I fiddled with intake valve springs, mixture, timing and swapped plugs to no avail.  Now, I wish I'd kept the 'borrow' of the variable speed drive so I could belt the engine up and motor it at a low rpm until I got things adjusted right.  For a while, it was running on it's own but poorly.  AND my arm is sore from spinning the engine.


I'll get back to it in a couple or three days.


15 February 2008:

Today was a short shop day.  I tried an idea that had been percolating for a while.  I made stronger valve spring so the valve would close 'smartly' and keep the intake runner explosions from happening due to slow closure of the valve.  This made it even more persnickety!  I then had the brainstorm to make the stronger spring almost long enough to contact the keeper when the valve is closed.  I then made another spring, larger in diameter but much weaker to close the valve with very little force.  A new keeper washer has a groove in it to keep the larger, weaker spring concentric with the stronger one.


The theory of this is that the valve needs to crack open easily to let in the maximum amount of fuel/air but, once open, must have a strong enough spring to snap it shut quickly.  Time ran out before I could test the arrangement but I don't think it'll make a whole lot of difference in the overall running of the engine.


I seem to be getting really hard hits when it does fire, hard enough to shake the table the engine's sitting on.  This could just be the normal Lenoir cycle sound or it could be detonation.  I may try regular gasoline instead of the naptha to see if it will fire 'softer' with higher octane fuel.  If that is not successful, I could make a head spacer to increase the head space to see if more volume will help any.  


17 February 2008:

I got the engine to run a little better.  Let me explain how.


Note: Engine bore = 2.750"  -  Engine stroke = 2.536"  -  Engine swept volume = 15.063 cubic inches


It was suggested by one reader of this page that Lenoir engines actually had quite a bit of head space so I made a really thick head gasket (0.129") and added it to the gasket I've been using (0.063") and an earlier gasket (0.027"), bringing the combustion space from 0.062" to 0.218".  I also figured the ratio of volume between the time the piston is at the top of the stroke and the bottom and got 40.9:1.  With the new larger head space, it is 11.68:1.  In an Otto cycle engine this would be the compression ratio.


On the left is the double-concentric valve springs, temporarily used.  On the right is the setup as I left it running best of all since the intake modifications.  I found that the concentric valve springs weren't needed so I removed the strong (small diameter) spring and left the weak one.  The ignition timing is about 55 degrees after TDC and this also agrees with what the guy said about his Lenoir.


After fiddling this to the point of boredom, I think I'll either make another thick gasket and add it to the pile, lowering the ratio to 7.31:1 and see if that helps.  If I think I'm on a roll, I can make a 0.5" thick aluminum spacer to get the ratio down to about 5:1 (slightly lower if I count the two head gaskets it will require.  That way, if I get really disgusted, I can just convert it into an Otto cycle engine!


18 February 2008:

Well, I think I've turned the corner today.  The engine ran faster than it has ever done, about 400 RPM by my guesstimate.  (24 March note: Originally, I put the number down as 2,000 RPM but, after thinking about it, I corrected it to the number you see).  Here's what made it run so much better.

Here's the spacer that lowers the volume ratio.  It goes between the head and the block.


I made the spacer out of a piece of cast aluminum I had around.  It is 0.625" thick and, with one 0.027" thick gasket between it and the head and the spacer and one 0.062" thick gasket between the spacer and the deck, I get a volume ratio of 3.55:1.



Here's the engine running right along with the spacer in place.  In the right-hand photo, I turned off the flash so you can see the motion.


It only took a little fiddling to get it to run pretty well and some intake valve spring changes were made to try to stop the backfiring.  Nothing I did to the spring stopped the popping and finally, I put my hand next to the exhaust port and it was backfiring out the exhaust port, which is something new.  Looking down the port at the valve head, I can see fire every time it backfires.  I held up on the valve stem to add to the spring force and it didn't change so the valve is seating all right.  This is a good omen (I think)!


Since it was so happy running, I just let it backfire.  It seems it backfires the most when the fuel mixture is optimum.  Another discovery is that the engine makes the highest RPM with the timing set to only 5 degrees past top center.  This means that the engine is only admitting fuel for about 5 degrees of crankshaft rotation and the expansion of the burned mixture is pushing the piston all the way down.  I think the backfiring is caused by the fuel having not burned completely by the time the piston is close to the bottom of the stroke and the exhaust valve opens.


It "4-cycles" regularly for some reason and mixture adjustment can't get it to "2-cycle" (fire every revolution) as it should.  It may be that when the intake valve snaps shut upon ignition of the charge, it sends a shock wave (and some exhaust gas) back through the mixer and causes the next intake cycle to be lean.  I looked very carefully at the flutter choke and can't see any sign of this, though.  If it can be made to fire regularly, I think some useable power can be extracted.


I quit for the day at this point and will think about the latest developments to try to get it to run even better.  


Since I have the exhaust valve timing set to open the valve about 10 degrees before BDC and close about 10 degrees BTC, some cam timing and duration adjustment is in order.


19 February 2008:

First thing today, I experimented some more with timing and had it running fairly well.  It was still 4-cycling, though.  Then, I noticed that oil was seeping out of the head spacer.  First, I thought the gasket was leaking but, while it was running I could see small bubbles coming out of the spacer itself.  I knew the casting had some sand voids in it but didn't know that some of the void tracks ran a long enough distance to cause problems.


The above photos show the void areas that had to be sealed.



After thoroughly cleaning all oil from the area, the spacer was heated until it was just too hot to touch.  In the left photo, JB Weld (metal-filled epoxy) is being buttered over the affected areas.  In the right photo, the whole works was heated again to help the epoxy flow into the voids.


The part was heated in order to drive out all the remaining lacquer thinner that was used to clean it.  In addition, the heat makes the epoxy much more liquid.  When the hot spacer cools off, some of the epoxy should be drawn into the porus area.


While the epoxy cured, I made a small butterfly valve for the intake runner so I cold throttle the engine.


After re-assembly, it was noted that the throttle did little to control the speed of the engine.  Ignition timing still has the major role in speed/power regulation.  The compression leaks from the voids are now fixed.


It ran all right for a while but, as it ran, it got weaker and weaker.  I looked for more leaks in the spacer and head but found none.  Then, I noted that there was more breather smoke coming out than normal.  When I stopped the engine (it almost stopped by itself), I checked the valves and they were seating.  Turning the engine backwards (so it would have compression), it was noted that where there was normally a lot of compression, there was almost no compression at all.


Turning the engine, I could hear a squeak coming from the cylinder area.  I think the piston skirt has collapsed or it's got broken rings.  Since the original (Tecumseh??) engine was designed for maximum pressure to be at or just after the top of the stroke, maybe the stress from running it with the maximum pressure point far down the stroke caused the side thrust on the piston to be strong enough to break the skirt.  It sure did rap when the timing is set later than about 70 degrees!


Tomorrow, I'll tear it down to see what the matter is.  I may be in the market for a piston and rings.


20 February 2008:

The engine is disassembled and nothing major seems to be wrong.  Just for the fun of it, I measured the end gaps of a couple of the rings.  Wow!  The oil ring had a gap of 0.232"!  The top ring has a gap of 0.050".  Methinks that it will need a set of piston rings!


I measured the skirt clearance and it is about 0.010", not too bad.  The top two ring grooves measure 0.082 wide and the oil ring groove measures 0.188".


Now, all I've got to figure out is what make of engine it is so I can buy some new rings that I can gap correctly.  The engine has a bore of 2.750 and looks hardly worn at all.  The stroke is 2.536, the nearest fraction to this number being 0.53125" or 17/32", making the fractional bore and stroke 2-3/4" X 2-17/32".  It seems kinda odd but that's what I measured.


In looking at the pictures of the block I'm using, does anyone know what make and model of engine it is so I can order rings?  I -think- I heard the name Tecumseh when I was given the box of parts.


28 February 2008:

The new rings arrived from Otto Gas Engine Works.  Dave Reed got them out within a day from the time I ordered them.  They're now in the engine and partly broken-in AND my arm is sore from cranking.  It wasn't what you'd call tight, just had some drag and didn't want to run.

After fiddling around with cam and ignition timing I had it up to a blistering 314 RPM, as shown on my newfangled optical tach.


I got tired of stinking up my shop so I made a scientific exhaust system.  You can see the plastic hose that wanders around and out the window.  I had to quit when the hose started melting.  I gotta get something a little better.


Here's how the timing worked out today at the time I quit and it was running pretty good.  The exhaust valve is set to open at 170 degrees and close at 332 degrees with ignition occuring at 345 degrees.  Wierd!  I'm going to have to cogitate on that a little.  I did notice that it was 4-cycling, never hitting twice in a row so I think what's happening is that with ignition occuring 15 degrees BTDC, it's lighting the charge from the previous stroke.  When the charge is lit, the intake valve does not open at all on the intake/power stroke because there is pressure from the combustion that was started at 15 degrees BTDC.


With the charge burned up, when the plug again fires at 15 degrees BTDC, there's nothing to light so it then gets a full intake stroke which is lit the next time the plug fires at 15 degrees BTDC.


Now, if I retard the ignition timing until it fires well after TDC (where it should be firing), it makes very little power and can't carry itself for long and sounds like it is pinging lightly.  I'm gonna think on that one for a while.


24 March 2008:

I done thunk on that one for a while.  What I had was a logical result of the exhaust valve closing way early.  Today, I made a chart and, using a DC motor as a generator and measuring the voltage output, I could make some fairly valid measurements.  I figure the belt loss plus the drag of the generator provided some load.  This is a little like a really sloppy prony brake, the voltage being relative to the crankshaft speed.  The Lenoiresque engine never produces very much power, just as the original Lenoir did but since the original was a double acting engine and was much larger, it produced a useable amount of work albeit at a very low effeciency.

I'll chart some of my valve and ignition timing settings and show the voltage at the generator:

Test Number:       1                  2                  3                 4                  5                  6

Exhaust open:    170 deg        179 deg        179 deg        165 deg        165 deg        155 deg

Exhaust close :   359 deg        359 deg         10 deg          11 deg          17 deg          17 deg

Ignition:               60 deg          59 deg           X                45 deg         47 deg          43 deg

Generator volts:   10 V             9.8 V             X                11 V            12 V            11.5 V

Since the apparent power output was at a maximum with the settings of test number 5 and declined with further advancing of the exhaust valve opening, at this time we can conclude that barring any other changes, that was the maximum power attainable.  


- In test number 3, performance didn't improve enough for me to take the trouble to measure the ignition angle or note the voltage output.  

- Most of the time, when the measurements, the engine was almost 2-cycling steadily as it should.

- All timing angles are After Top Dead Center.


After resetting the valve timing per step 5, I removed the generator load from the engine and did some ignition and fuel mixture tweaking to see how fast it would run and if I could get it to 2-cycle regularly.  I found that I could get it to 2-cycle pretty well with the ignition timing in the vicinity of 25 degrees.  On an impulse and with the engine running, I removed the exhaust runner and let the engine exhaust directly out of the exhaust port.  There was an approximate 100 RPM increase in speed with nothing else changed, making me think I need to enlarge the exhaust port.  After tweaking the fuel mixture, it was running 404 RPM and the engine was 4 and 8-cycling.


I then set the ignition timing to approximately 45 degrees and measured the RPM at 270 with the engine pretty much steadly 2-cycling as it should.


The final test at the step 5 valve settings was for maximum RPM.  Timing and mixture were tweaked and the intake valve spring tension was increased a little and the maximum it could do was right at 520 with much spitting out the exhaust.  I have the feeling that "the timing uncertainty" of the atmospheric intake valve is partly to blame.


I also noticed some slight leakage around the intake valve cage so, when I have it apart to enlarge the exhaust port, I will take a look to see if I can see where the leakage is coming from.


21 December 2010:

After procrastinating for a couple of years, I've finally decided to post a YouTube video of The Lenoiresque Engine.


For this run, I set the valve timing so the exhaust opens at 165 degrees past TDC and closes at 0 degrees, giving a duration of 205 degrees.  Ignition is set (variable) to around 10 degrees ATDC and it seems to run about as well as expected at these settings.


Here's the flick:

In case the above doesn't work (like on an Ipad)


23 December 2010:

Yesterday, I fiddled with the Hvid and thought about the Lenoiresque.  If you watch the movie, you will hear that the engine is only occasionally firing every revolution.  Most of the time, it fires every other revolution.  I tried adjusting the firing point and fuel mixture (pump gasoline which knocks less than naphtha) and only got it to hit twice in a row occasionally.


My theory is that, since I added the extra 9/16" of head space, it couldn't scavenge properly and the contaminated mixture needed an extra cycle to pass out of the cylinder.  To try to prove this, I removed the spacer and substituted a 1/8" thick gasket, giving a 1/8" head space.


As I thought, once running, if the ignition point was retarded (longer intake cycle) beyond a certain point, the engine would act like detonation was taking place.  This was alleviated by fiddling with the valve and ignition timing.


Presently, the exhaust valve still opens at about 165 degrees but I've now got it set to close at 355 giving a duration of about 190 degrees.  The engine runs fairly well at about 200 RPM with the ignition point at about 25 degrees ATDC.


I found that, if the exhaust closes past zero degrees (TDC), the intake cycle is naturally shortened and I suppose a little of the exhaust could be sucked back in.  With the large headspace, this timing seemed to work all right but with the small headspace, the exhaust sucking caused a drop in performance (if you want to call the way it runs "performance").


If someone knows what the valve and ignition timing of an actual Lenoir engine is, I'd really like to know.  As it is, with this engine, ignition varies from about 25 degrees ATDC for "idle" to about 40 degrees ATDC for speed.  Power is almost non-existent.


I don't know that we're accomplishing anything much

- but -

BOY!  This is FUN!

Stay Tuned!  I'm always happy to hear your comments and suggestions.  Please email me at:

[email protected]