| jfarrell | -- 07-11-2012 @ 4:14 PM |
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I've got a problem. The flathead engine in our 49 Ford was just rebuilt. I've put 44 miles on the engine. Because the intrument panel oil guage read 20 lbs of pressure or less, even on a cold engine, I replaced the sending unit with a mechanical guage. It still reads 20 lbs or less on a cold engine. Everything inside the engine is new. Any suggestions on how to troubleshoot from this point or suggestions on what could be wrong? Thanks. Jim Farrell
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| supereal | -- 07-11-2012 @ 4:28 PM |
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As an engine rebuilder, I can say that there are many possibilities, all of which will likely require pulling and disassembling the engine. The 8ba type engine uses a different oil pump pickup from the older type. It uses a press fit tube that tends to come loose. We braze them, just to be sure. The pressure relief valve on the pump may have a weak spring. If the cam, main, and rod bearings were not properly sized, that could account for it. I'd have a talk with the rebuilder. I hope you have some kind of warranty.
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| ford38v8 | -- 07-11-2012 @ 7:41 PM |
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With only 44 miles on the engine, you may not have a problem at all. New engines require a break in period to seat the rings. 20 lbs pressure is adequate to provide lubrication under mild runniung conditions. Log your pressure, mileage, and ambient temperature each day you drive, and watch for some improvement, which youshould see before your 500 mile oil change. Alan
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| supereal | -- 07-12-2012 @ 6:03 AM |
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Could be, Alan, but I'd be concerned about the low cold starting pressure. A 40 lb oil pump should produce more than 20lbs at that time. Piston rings do affect oil consumption, but not pressure. A loose bearing (s) certainly would. We always examine all bearing inserts before installation. It isn't rare to find one or more sets of the wrong size mixed in a box set. It only takes one to affect system pressure. We open all the crankshaft plugs to clean the oil passages on old ones, then tap and replace them. It is possible to lose oil pressure if any are leaking. I wouldn't run an engine with such low cold pressure, as damage is likely.
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| Stroker | -- 07-12-2012 @ 7:01 AM |
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One additional thought....you didn't mention what you were using for oil. Oil viscosity can greatly affect cold start-up pressure. I'll "side" with Super though regarding the fact that the problem isn't going to improve after additional miles. It's time to find the cause; correct it, and hope that you were just lucky enough to get two really pessimistic pressure gauges.
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| deuce_roadster | -- 07-12-2012 @ 7:04 AM |
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I would agree with Super on this. I thought the 8ba engines had 80lb pumps in them but even with a lower pressure pump there must be something wrong. If there is no external leak it has to be an internal leak of some kind for a newly rebuilt engine to have only 20 lbs pressure cold. I would suspect poor bearing clearence somewhere or maybe a defective releif valve. If the engine is quiet, maybe mains or the cam. Must be very disappointing, sorry you are dealing with this. I hope the rebuilder stands behind the job.
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| TomO | -- 07-12-2012 @ 8:02 AM |
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I agree that you should have more than 20# pressure cold and I doubt that it will get better with driving. An 80# pump should deliver at least 50# cold with 10W30 oil and you should not be using a thinner oil than that. I would go back to the rebuilder and ask his opinion of what should be checked first. Tom
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| joe b | -- 07-12-2012 @ 12:18 PM |
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Just a thought but it could be your sending unit. I installed a new crank and bearings in my '41 engine. It always had good high oil pressure. I decided to put a new sending unit on the engine for appearance as the one on the engine was dented here and there and looked bad. I ordered a new 80# unit. The engine oil pressure never got above 20# no matter what. This with 20-50 oil. Another sending unit and I was back in business. Either the part was mis-stocked or it is another example,of foreign cr*p. Ask your builder about the sender-you never know
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| supereal | -- 07-12-2012 @ 5:47 PM |
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I mentioned the 40# pump to say EVEN with a 40# pump, the cold pressure should be higher. I didn't say it quite right. I doubt the sending unit is at fault, as the post said the low pressure was verified with a mechanical direct gauge. This message was edited by supereal on 7-12-12 @ 8:19 PM
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| mdurhan | -- 07-14-2012 @ 3:04 PM |
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I'll be begging your pardon, Alan, but piston rings really have nothing to do with oil pressure..... Bearings? Yes. Oil pump? Yes. Oil pump by-pass valve? Yes. Oil viscosity? Yes. Mike There are more "barn finds" than barns.
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| mdurhan | -- 07-14-2012 @ 3:05 PM |
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Delete. (Duplicate) This message was edited by mdurhan on 7-14-12 @ 4:13 PM
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| ford38v8 | -- 07-14-2012 @ 9:37 PM |
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With everyone ganging up on me, I guess I'll just admit defeat and slink away to lick my wounds! Alan
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| keith oh | -- 07-15-2012 @ 7:57 AM |
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If you have a bypass oil filter make sure the restrictor fitting has been installed on the "in" side of the filter.
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| Old Henry | -- 07-15-2012 @ 8:57 AM |
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ford38v8, I'll side with you that 20 lbs. pressure is certainly enought to lubricate the engine. It's not pressure that lubricates but flow. If you have any pressure at all you have flow and that's all that counts. I ran many years with that pressure or lower. Even now with new rebuild and new pump I'm still not much above 20 lbs. after warming up. I personally think that low oil pressure is one of those "phantom deamons" that plague flathead engines like oil leaks that are really not much more than that - phantom deamons. Old Henry (The older I get, the better old looks.)
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| supereal | -- 07-15-2012 @ 2:15 PM |
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It doesn't matter whether the oil filter restrictor is in the input or output side of the filter. We usually put them on the output so the full flow reaches the filter element first. The restrictor is necessary to prevent starving of the oil flow by bypassing the regular channels.
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| jfarrell | -- 07-15-2012 @ 6:37 PM |
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I'm using 20-50 Castroil. The oil filter is hooked up using stock lines. I've put a wire through the lines to make sure they are not plugged, and they aren't. How do I tell if the car has a oil filter restrictor? Thanks. Jim Farrell
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| keith oh | -- 07-15-2012 @ 6:44 PM |
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Whether restrictor is on the in or outside flow through the bypass filter, oil pressure will not read accurately if not restricted. Pressure will show faster if it is on the in side of the filter.
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| supereal | -- 07-16-2012 @ 7:38 AM |
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This discussion regarding filters has opened another thought on why a newly rebuilt engine has low oil pressure. It is possible that the filter restrictor was left out, or the orifice is too large. We solder the fitting shut and drill a 1/16" hole in the plug. Anything larger will cause low pressure by bypassing oil flow. Most of us were assuming that the engine had decent pressure before the work. I'd look at the restrictor before taking the engine apart. The main virtue of the bypass type filter is allowing an extra quart of oil to the correct four quart fill. The filtering action is low, at best.
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| deuce_roadster | -- 07-16-2012 @ 9:17 AM |
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By taking the oil filter out of the equation with a pipe plug you may have an "Ahh HA" moment and have the problem figured out. I hope it is as simple as no restriction at the filter.
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| jaxV8carz | -- 07-16-2012 @ 10:54 AM |
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Does the restrictor orifice at the oil filter canister inlet have any effect on oil pressure?
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| supereal | -- 07-16-2012 @ 11:24 AM |
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Yes.
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| jfarrell | -- 07-16-2012 @ 6:44 PM |
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I disconnected the lines and fittings to the oil filter. I ran a wire through both lines. They are both open. The line that goes into the side of the oil filter canister has a brass fitting at one end that goes first into the canister. The steel fitting on the end of the line goes into the brass fitting. The brass fitting has a very small opening on the end that threads into the canister. I put a 1/16" drill bit into the end of the brass fitting and it fits. A larger bit will not fit. Am I correct that the brass fitting is the restrictor? Am I also correct that what I described sounds like there is a restrictor in place that it is probably the correct size? If so, it looks like next is to pull the pan and look at the oil pump? Thanks to everyone. Jim Farrell
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