Oil pressure on Allis CA

[Wolfgang]

To all you mechanical wizards: My 1953 Allis CA initally was raised on 30W non-detergent. Recently I went to 10W-30 high detergent. Noticed little decrease in oil pressure, ran 20hrs +, changed oil. Put same 10W-30 back in, noticed a loss of oil pressure again. Few days back hauling a load of firewood, approached steep grade....you know the type.....engine holds back but just can"t. Right after that oil pressure went to almost nothing. Engine runs fine, temp very normal, oil pump works cause it sprays like crazy with oil filter off, and engine is full, oil filter and housing full. Can you fellows help me out. Do I have a bad oil gauge?
Thanks
 

[Jerry Coulter]

You might have sludge choking up the oil pickup screen. Might be best that you drop the pan and give the lower end a good cleaning.
 

[old]

10W-30 oil is really 10W oil with additives that in theory make it act like a 30W oil when warmed up. Bet if you change the oil to a straight 30W detergent oil your pressure would come right back to what it had been in the past
 

[ddl]

Did you change the filter? I have heard that different filters will mess with the pressure. I replaced my canister with a regular encased filter so i don't know if this is true or not.
 

[steve(ill)]

may not help, but just FYI... the pump puts out a fixed volumn. The filter is packed with cotton swab and is very restrictive. THE filter allows 15% of the oil from the pump to go thru it and dump back to sump. The remaining 85% of the oil goes thru the cam shaft and sprays thru orifices at the bearings on the crank and pistons. There is also an external oil line going to the head that lubes the rocker arms and valves..You dont necessarily need high pressure, you need flow. THe PSI gauge is just a way to verify flow. Filter should have a 1/4 inch steel tube inside it with a 1/8 inch hole (i think) to regulate the flow thru the filter and back to sump. Thicher oil, more restrictive filter, smaller hole in the filter tube, and good pump seal faces are all ways to increase flow and pressure.