| Flatbob | -- 07-28-2012 @ 7:27 PM |
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The engine in my '36 has slightly over 300 miles on it and the first start of the day oil pressure is 10-12 lbs. at idle and increases to 30lbs. at about half throttle. After driving for 20 minutes or so I can only maintain about 12lbs. at 40 MPH, is this adequate oil pressure? Am using the stock oil pressure sending unit. This message was edited by Flatbob on 7-28-12 @ 7:34 PM
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| supereal | -- 07-28-2012 @ 7:37 PM |
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What type and viscosity oil are you using?
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| supereal | -- 07-28-2012 @ 7:38 PM |
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What type and viscosity oil are you using?
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| Flatbob | -- 07-28-2012 @ 10:56 PM |
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Super, am using 40W Pennzoil with ZDDP additive; I'll have to check bottles to see if non-detergent or detergent if it's relevent. There is little to no smoke coming out tail pipe. The OAT was in the low 100's but the car wasn't overheating and running smoothly. This message was edited by Flatbob on 7-28-12 @ 10:58 PM
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| supereal | -- 07-29-2012 @ 9:05 AM |
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Many of us use 20W-50. It is light enough to allow faster cranking, but the higher viscosity aids in keeping the pressure up when it is hot. ZDDP additive isn't necessary in your flathead engine, unless it is being run for the first time after a rebuild. Use only detergent oils. Once the cam lobes and listers are coated, regular oil is sufficient. Avoid synthetics, as they tend to leak past the old style seals. If you have an oil filter, 5 quarts is the refill. Four is the right number without a filter, regardless of what the books say. Overfilling adds to leaks, and may cause oil aeration if it reached the crankshaft weights. Widely fluctuating oil pressure, particularly when hot, really spooks newcomers to the flathead. Engine clearances are much wider the modern engines, and even when the gauge says it is near zero at idle, the bearings are safe. Just drive and enjoy the ride! This message was edited by supereal on 7-29-12 @ 9:06 AM
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| Flatbob | -- 07-29-2012 @ 10:54 AM |
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Super, thanks for the reassuring advice. I rebuilt the engine myself; it was my first flathead rebuild and therefore have some self doubt. At 300 miles can only get 90lbs. compression and 15-16" of vacuum, am wondering if I installed oil rings upside down on my 4 ring pistons. Will switch to the 20-50W detergent. This message was edited by Flatbob on 7-29-12 @ 10:56 AM
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| alanwoodieman | -- 07-29-2012 @ 12:33 PM |
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vacuum can go up if you adjust the timing a little,up a line on the distributer timing. did you hold the throttle wide open when checking compression? with all the plugs out? squirt a little light weight oil into the cylinder and see if the compression readings go up
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| supereal | -- 07-29-2012 @ 2:31 PM |
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If the oil rings were incorrectly installed, you will see some increase in oil consumption and a bit of blue smoke, but compression won't be affected much, if any. If you didn't hone the cylinders to break the glaze, it will take a long time for the rings to seat. Ninety pounds isn't great, but certainly acceptable. Honing provides a new surface to aid ring seating if done correctly. It is likely, in any event, that compression will improve with additional mileage, in any case.
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| Flatbob | -- 07-29-2012 @ 2:48 PM |
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Perhaps if I can be patient I will see an improvement in compression at 500 miles?
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| supereal | -- 07-29-2012 @ 5:08 PM |
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Probably, but I wouldn't worry. Drive and have fun!
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| doning | -- 07-30-2012 @ 12:23 PM |
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Super: What should the compression be? Compression readies the same for '37 85 HP?
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