Allis C Oiling System

Jaden

Member
Location
Eastern Nebraska
My "C" has a problem where the engine will lock up after a few minutes of running, even though oil pressure remains 15 PSI. Dick L. has previously posted some good pictures showing internal oil flow. These pictures are from the outside. I am listing my assumptions. If anyone sees a mistake, please correct. I am wondering if a line plugged.
A= Filtered oil return passage to oil pan
B= Oil supply to bottom of filter and pressure guage
C= Supply from pump
D= pipe to up
E= Side of tee- oil to camshaft
F= Oil to rockers
a226088.jpg
 
Define "locks up". As in she get so tight it won't turn over by hand? If that is the case, you just as well buy a rebuild kit and fix it. How long does it need to sit before you can get it to turn over again? Does it have any coolant in it? Sounds like the pistons are getting hot and getting tight.
AaronSEIA
 
Oil pressure in not an indicator that the bearings are or not being oiled in this engine like most. Oil pressure is built between the filter and the pressure regulator in the stem of the oil pump. In this system oil is delivered to the bearing from free flow oil being flung (centrifugal force) from the center of the camshaft thru the cam bearings to the main bearings. It is also flung out little holes in the camshaft onto the rods that is then picked up with the holes in the base of the rods as they spin and forced into the rod bearings.

StuckAllisCEngine-vi.jpg


With this system all the bearings can be totally shot and still have good oil pressure. There is no way you can find your problem without removing the pan and checking each bearing.
 
Engine pulls down and stops. You can't turn it with a crank unless you wait about 20 minutes. Doesn't seem hot as in lack of coolant. I would like to identify the problem before rebuilding it.
 
Additional info: I had the pan off and checked and fitted the rods about 6 months before. All looked good. This occurred just after I changed oil and filter. The filter is a Purolator L30007.
 
If you remove shims from the bearing caps without filing the ends of the bearing shells you can get enough bearing crush to pinch in on the crankshaft.

If it were mine I would remove all the spark plugs, drop the pan and loosen all bearing caps. I would tighten each cap one at a time and had crank the engine over several times before tightening another cap. You should be able to find a tight bearing. When working on a crankshaft that has not been fresh ground it is best to check clearances with the rods as close to 90? from bottom as possible and get the caps back on. The narrow diameter of the crankshaft journal will be with the rod straight down. It will be a little wider on the sides when it is down. If you have .002 wear out of round on the crankshaft and you set your clearance at .002 with the rod down you would have .000 on the sides. If the crankshaft is only out of round by .001 and you set the clearance at .002 and you did not file the thickness of the shims removed the extra bearing crush could easily be .001 which could give you .000 clearance on the sides. (when you crush something it gets wider) The rod being stronger than the bearing shell when you over crush it, it only has one way to go and that is in toward the crankshaft journal. That becomes a break!
I hope this explains some of the (possible) problems and a place to check.
 
I had that problem and it was lack of coolant. If it was oil and a bearing locked up, you would hear a knock next time you startup... Low water or lack of flow will allow piston rings to lockup a motor. Let it set 30 minutes and it will startup and run OK... NO KNOCK.. I would flush the radiator and block and check pump flow.
 
I have a B that would lock up solid after about a few minutes work. It would then start and run good after 20-30 munutes.
I pulled the engine and tore it down. What I found was the #2 connecting rod pinch bolt that secures the wrist pin was not holding the wrist pin tight. The wrist pin wound move over and scrape on the cylinder wall hard enough to lock up the engine.
I suggest, pull the head and look at the cylinders, I bet you'll
find a big gouge on one of the cylinder walls.
 

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