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Oilpressure


birger

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Dear Birger,THIS is a common problem for a V-12 and the flathead Ford,YEAH RIGHT tongue.gif.Are there any oil passages in the block that should be restricted or not restricted with the SWITCH to hydraulic lifters????Are you using the appropriate oil pressure sending unit with the pump you are using????I would think 10 or 15 pounds at hot idle and 30-40 going down the road would be normal.diz smile.gif

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the high capacity pumps are usually set at 80 psi relief pressure. If the oil galley line for the the lifters has the regular bypass valve(rear of engine) and relief valve at the front of the engine you should be ok. The correct relief pressure at the front of the engine will restrict oil pressure to the lifters to 20psi so high line pressue in the rest of the system shouldn't effect the lifter operation. Any "looseness" or excess crankshaft end play in the rear main may lead to leakage at the slinger seal in the rear main, especially if the drain tube on the rear main cap is partialy plugged with sludge. If the rear main is not leaking then you may be ok. The V12s are all equipped with 50 psi sending units and gauges so you could be running higher pressure at higher rpms. If the car runs fine and you are not using/leaking excess oil I wouldn't worry. One fix would be to install a relief spring in the oil pump to limit pressure at 50 psi and keep the advantage of the extra capacity of the 80#, high volumn oil pump. Normal oil pressure for these cars was listed in the owner's manual at 30 to 45 psi at 2000 rpm.

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Guest imported_V12Bill

Hey guys! Birger says he has 15 - 20 PSI at idle and 50 PSI at fast idle or rev. He doesn't say whether or not the engine has warmed up or is still on the cool side. What is wrong with those numbers? Most people would be glad to know that the needle will go to 50 PSI on their V12. Birger does not state whether or not the lifters clattered. I have to assume that they did not.

I would say that a V12 with the engine warmed up and using 20W 50 oil showing those numbers is ok. I believe the owners manual says 20 PSI on a warm engine at 50 MPH in high gear.

Bill

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Guest imported_V12Bill

Birger, I had a problem with noisy lifters on an engine that I had rebuilt and had set aside for several months to do other work on the car. I just let the engine run at a fast idle(1000 RPM or so) for about 20 minutes and it quieted down. Try that before you tear down the engine.

Bill

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Guest imported_V12Bill

Birger, The check valve ball can be replaced. I went to a bearing supply store and bought 100 ball bearings to fit. I think the size was 3/16and the cost was 1 cent each. I drove out the ball cage and cleaned up everything in lacquer thiner and reassembled all. I did this to all 24 lifters and have not had any additional problems. Lifters are in very short supply and we should all try to save the lifters we have.

Bill

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Looks like our tech experts have jumped on the problem. Some other observations, somewhat related....I don't know what year your car is, but I'm pretty sure the oil pressure gauge on pre-war cars doesn't go above 50 psi anyway. But as more knowledgeable folks have already said, your numbers sound fine.

Another interesting tidbit I learned about while reading old TWOTZ issues: all HV-12 cars take an oil pressure sending unit calibrated for 50 psi, while later, more common Ford units are calibrated for 80 psi. If you use the later one in place of the correct, earlier one, your pressure readings will be 5/8th of the true level. So if any of you are getting low readings, you might just quickly check whether you have a "50" on the stem of your sending unit or not.

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