Compression test C113 engine

[48SuperAIndustrial]

I'm starting to do some work on my '48 Super A Industrial tractor and I have some questions. It's magneto ignition, a bit hard to start and once it's running it smokes, not heavy, but constant light smoke. Radiator stays full and no oil film on the coolant so I'm not worried about head gasket leaks.

What's a typical cylinder pressure reading for a C113 in a 1948 Super A?
I don't have a 6 V battery in the machine now. Can I get accurate enough cylinder pressure readings if I hand crank it over making sure the cylinder I'm checking goes through multiple compression cycles until my gauge reading maxes out?

If I need rings and liners, any recommendation on best suppliers? How about miscellaneous gaskets? I'm looking for good quality and not the lowest price. If I need to rebuild, I only want to do it once. The tractor is retired from use so this refresh should last decades.

Thanks in advance. Mike

[tst]

you can use a 12 volt to test it, doubt if you can crank it long and fast enough by hand, a good engine can hit a 150 lbs tight and fresh, about the lowest you want is 90 lbs for iiot to be useful at all, check the plugs for sight of antifreeze when you pull them

[Bill V in Md]

I would also run the engine to warm up, followed by turning fuel off, switching magneto off, removing all spark plugs, leaving choke off (open) and opening throttle wide open. Use the starter and allow it to crank over at least 6-8 times.

[48SuperAIndustrial]

Thanks for the advice. It'll probably be a week or more before I get back to where the tractor is stored and have time to run the test. Any advice on rings and liners if I determine I need them down the road?

[tst]

best way is a cylinder leak down test

[Eugene]

Can I get accurate enough cylinder pressure readings if I hand crank it over making sure the cylinder I'm checking goes through multiple compression cycles until my gauge reading maxes out?

Your compression reading will be about 60% of what you would get using the starter. The results may not be as uniform as using the starter.

[48SuperAIndustrial]

Thanks. Everyone brings up interesting points and it's got me wondering why cranking speed would have an effect on the psi. When I hook up the gauge, I'll do a test with the starter followed by a test cranking by hand to see if there is a PSI difference.
The compression gauge has a check valve that holds pressure until I release it and when I check compression on a single cylinder rope start engine, I can see the pressure build in the gauge as I pull the rope several times until the gauge pressure maxes out after 5 or 6 compression cycles.

[tst]

big difference turning a single cyl engine by hand and a 4 cyl tractor engine

[48SuperAIndustrial]

Thanks. I've been cranking it for about 55 years and I think my right arm is bigger than my left from the work out some days. I'll keep a log of the readings cranking by hand and with the starter and I'll also do the leak down test you advised and I'll post the results.

[getitrunning]

if you have it running it might be good to get it up to temp and run some sea foam or OMC engine tuner or other similar product though it to cut though built up carbon in the engine. something like that may just fix the smoking problem. an engine will not run or have severe lack of power if compression is too low. cranking the engine over several revolutions till the compression gauge maxes out and the needle in gauge will go no higher will get you accurate reading.

[48SuperAIndustrial]

Thanks. The engine does run and the tractor drives fine. It was used weekly to cut a couple acres up until 2012 when it was retired. For the last 11 years, it has only been run and exercised once or twice a year which is not enough. I've regularly cranked the engine over once or twice a month so it has stayed free, however, it is probably carboned up and maybe a ring or two is stuck or maybe all the rings are worn. It has probably been 20+ years since it's last rebuild.