| 6lucky13 | -- 10-21-2013 @ 3:21 PM |
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I'm planning to switch from 10w-40 motor oil in my '37 engine to 20w-50 oil. Should I expect to see a difference in indicated oil pressure? The motor currently runs at about 20 lbs at idle to 30-35 while driving with the 10w-40. Jon
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| Old Henry | -- 10-21-2013 @ 3:32 PM |
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I got 5 psi more from changing from S.A.E. 30 to S.A.E. 40 (I don't use multi-vis oil if I can help it.) Old Henry (The older I get, the better old looks.)
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| supereal | -- 10-21-2013 @ 4:05 PM |
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I have used Castrol 20W-50 for years. It helps maintain pressure when the engine is hot, yet allows good cranking when cool. When I take an engine apart using this oil, it is very clean.
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| joe b | -- 10-22-2013 @ 7:00 AM |
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I also have used Castrol 20/50 in my '41 for 16 years. I agree with Super. I did change to 40wt and a quart of Marvel Mystery Oil to try to cure a valve problem. My oil pressure dropped significantly. This attempted fix did not work and I went back to Castrol. Oil pressure is back to what it was.
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| keith oh | -- 10-23-2013 @ 7:44 AM |
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I do not know what the rational for using MMO for low oil pressure was, but for your "Valve Problems" dribbling MMO through each side of your carburetor with the engine running at a fast idle stands a much better chance of relieving valve problems.
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| joe b | -- 10-23-2013 @ 1:35 PM |
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Keith, I also did that but it did not fix the problem. Some suggested to use MMO in the oil so I tried it as I thought what have I got to lose?
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| supereal | -- 10-23-2013 @ 8:41 PM |
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I wouldn't expect valve problems unless it was confirmed by a dry/wet compression test. MMO may have its uses, but it can, and will, cause spark plug contamination. Adding anything to the fuel or down the carb before properly diagnosing a problem is a waste of time and money. Adding it the oil can result in loss of effectiveness of the package of the oil's carefully engineered additives. This message was edited by supereal on 10-23-13 @ 8:44 PM
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| joe b | -- 10-24-2013 @ 6:02 AM |
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Super, that is exactly why I changed the oil after about 85 miles with the MMO. Could you explain the "dry-wet" compression test? I have only used the tester dry I think.
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| supereal | -- 10-24-2013 @ 7:45 AM |
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Remove all spark plugs from the engine, and block the throttle open. Test each cylinder and note the compression. Then, squirt oil into the cylinder and retest. If the compression goes up, the rings are worn. If not, the valves are not sealing. Doing diagnosis saves lots of time when tracing problems. Just guessing almost always results in complicating the situation.
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| supereal | -- 10-24-2013 @ 7:45 AM |
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Remove all spark plugs from the engine, and block the throttle open. Test each cylinder and note the compression. Then, squirt oil into the cylinder and retest. If the compression goes up, the rings are worn. If not, the valves are not sealing. Doing diagnosis saves lots of time when tracing problems. Just guessing almost always results in complicating the situation.
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| TomO | -- 10-24-2013 @ 8:33 AM |
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High oil pressure is not necessary for engine longevity. Many Fords and Chevy's have given long service with oil pressure in the low teens. The oil has to be clean and the oil passages must not be clogged to get long engine life. The main reason you should monitor the oil pressure is for a change in the normal reading. If your oil pressure drops when accelerating, you may be low on oil. If your oil pressure drops from its normal range, you should check for a failing pump or worn bearings. The oiling system on the flatheads was designed to use 30 weight oil in the summer and lighter weight oil in the winter. 10W-30 is equivalent to 30 weight when the engine is at operating temperatures and 10W when the engine is cold. The multi-viscosity oils are superior to the single viscosity oils in that they flow better when the engine is cold and give the same protection when the engine is at operating temperatures. Tom
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| TomO | -- 10-24-2013 @ 8:44 AM |
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High oil pressure is not necessary for engine longevity. Many Fords and Chevy's have given long service with oil pressure in the low teens. The oil has to be clean and the oil passages must not be clogged to get long engine life. The main reason you should monitor the oil pressure is for a change in the normal reading. If your oil pressure drops when accelerating, you may be low on oil. If your oil pressure drops from its normal range, you should check for a failing pump or worn bearings. The oiling system on the flatheads was designed to use 30 weight oil in the summer and lighter weight oil in the winter. 10W-30 is equivalent to 30 weight when the engine is at operating temperatures and 10W when the engine is cold. The multi-viscosity oils are superior to the single viscosity oils in that they flow better when the engine is cold and give the same protection when the engine is at operating temperatures. Tom
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