We recently got our 1947 WC Allis Chalmers running after it had been in storage from '88 to '04. For the first 3 to 4 hours of running the oil pressure was always in the middle of the normal range (the gauge is new and only shows a normal range, not psi). A few days ago we drove it about 5 miles to the local county fair to run in a parade. About half way there the oil pressure started slowly dropping to the very bottom of the normal range. It was running fine, so we ran it in the parade and then drove it home (the oil pressure never got any higher). We started the tractor again this morning and the oil pressure was back in the normal range. The engine idled for about 15 minutes and the pressure dropped a little, but it was still in the normal range. We adjusted the idle screw and needle valve on the carburetor (they were set too rich). The oil filter is new (Agco brand), there is fresh 30w oil in the engine, new spark plugs (Autolite 295’s) and a rebuilt carb. The engine head had been removed and reinstalled (the engine rusted and the pistons got stuck while it was stored and the head was removed to 'un-freeze' it so it would start), but the gasket was not changed (it leaks). Also, the oil pan, push rod cover plate, and front crank shaft seals leak. Any ideas on why the oil pressure the pressure would suddenly drop so low like this? On shorter trips, the oil pressure never dropped significantly. The engine was rebuilt back in '81 (not sure what work was done on the camshaft and bearings) and only has about 25 hours on it. At initial cold start-up, there is some blue smoke out of the exhaust, but it eventually goes away, but while the engine is running, there is a slight smell of oil burning. We have not adjusted the pressure relief valve yet. Could the fact that the carburetor was set too rich have anything to do with this? Any ideas that any has on why the oil pressure would change like this would be greatly appreciated. Thank you.
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