slowing down engine

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Randy

Guest
I need some hints on slowing my McCormick Deering 1-1/2 down.

I have already retarded the ign timing to TDC, reworked the throttle plate to fit tighter, removed the throttle governor springs, lengthened the throttle rod to assure a closed throttle, Strengthened the intake valve spring.

That gets me about 150 RPM..

If I advance the exhaust valve it slows down more & if I place a spacer under the intake valve spring cap to limit intake valve travel I can get it down to around 100 RPM.. I feel it should easily go down to about 60 RPM’s but can’t seem to find a way to do it.. I have tried retarding the ign timing to after TDC but that seems to help very little & makes the exhaust louder & much hotter..

Any other suggestions from all the experts here?
 
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DICK GRAYBILL

Guest
Randy if you can get a 1 1/2 hp to run 100rpm I think you are doing very good. I'd be glad if I could get my Economy and Jaeger that slow. Dick in central Pa.
 
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Chuck Martin

Guest
Did you reduce the tension of the governor springs? Short of running it on the rich side, you could start working with fuel blends, try reducing the octane, or a slower solvent additive. I've had luck adding fuel line antifreeze to keep from running too rich at a slow rpm. (You can also run an engine with almost no compression on nitro methane) As when handeling and hazardous materials, take all required safety precautions! Good luck!
 
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Joe Morris

Guest
Randy, I'm afraid you are trying to accomplish something that is probably impossible on a throttled engine like the I.H.C. M engine. I have been fooling with old engines for many years and I have never seen an M that would run very slow. It' just not their nature. This can be probably achieved with most Hit and miss engines provided they are are of higher H.P. say like 3 to 6 and up. Smaller engines just don't have the flywheel weight to keep them turning very long before fireing again. I hope you achieve your 60 rpm goal. If you do let everyone know how you did it. Joe Morris
 
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Randy

Guest
Chuck, I have completely removed both governor springs & links.. The only spring tension left is the carb throttle shaft spring.
 
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Randy

Guest
Last night I did retard the spark just slightly more and restricted the intake valve travel a little more & did get it down to about 90 RPM's.. If I hold some drag on the flywheels I can get it down to about 35 exhaust firings per minute (probably about 70 RPM's but can't hold tension on the flywheels & use my hand held tac at the same time. Tonight I'm going to play with exhaust back pressure as it seems to slow down more if I hold my hand over part of the muffler..

Chuck, On the fuel volatility issue-- lower octane fuel actually ignites easier than higher octane fuel so that won’t help me. I have tried some kerosene in the fuel & while that does seem to help it also tends to foul the spark plug due to lack of combustion heat at real low RPM’s. Running rich does slow it down but it tends to foul the spark plug & I don’t like the trail of smoke coming out of the pipe.

Thanks for all the suggestions—I’m pretty sure I will get it down to 60 RPM’s if I stay after it. Any other suggestions please let me know.
 
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Kevin Hesse

Guest
I have a 3hp "M" that will run around 50rpm. I machined a venturi for the carburetor that only has a 1/4" throat and is about 1 1/2" long. also I made a idle screw so that I can adjust the throttle plate opening. lastly the timing is about 15 degrees after TDC
 
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Randy

Guest
Kevin, thanks for the input.. I worked on the 1-1/2 a little more last night and with some further intake valve movement restriction and a little more playing with the ign timing I did get it to run pretty even at about 68 RPM’s.. I don’t think I will be able to get the 50 RPM’s you are getting as the compression is pretty good in this 1-1/2 and the flywheels are lighter than yours so the flywheels actually stop for a moment at full compression at about 60 RPM’s.. I did manage to get it to run at about 60 RPM’s but it would tend to stall once in a while when the crank would stop turning at full compression. Actually 68-70 RPM,s sounds pretty good as that is about one firing pop just short of every 2 seconds..
 
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