1990 Ford 4.0 oil pressure

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cratemodel014
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1990 Ford 4.0 oil pressure

Post by cratemodel014 »

Hey guys I have a 90 ford 4.0 that has great oil pressure at cold idle(50psi). Once it warms up pressure drops below 5 lbs. Engine has been rebuilt. Crank was turned with fresh bearings, new cam bearings. As far as I can tell all oil galley plugs are in place. Also has a new oil pump. Any ideas on what is happening to my oil pressure when it warms up?
cratemodel014
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Re: 1990 Ford 4.0 oil pressure

Post by cratemodel014 »

Went to a mechanical guage. Dont have bearing clearances in front of me but if I remember correctly they were a little on the tight side. 5w30 oil
mag2555
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Re: 1990 Ford 4.0 oil pressure

Post by mag2555 »

Why was the motor rebuilt?
I never put a new oil pump in if its outputting good pressure and its clearances check good, as in it would not be the first time I have had new pumps with bad pressure bypass springs, or pressure check ball seats that where deformed!
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Keith Morganstein
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Re: 1990 Ford 4.0 oil pressure

Post by Keith Morganstein »

How is the pressure when rpm is increased?

Do you have a Fram filter on it?
Automotive Machining, cylinder head rebuilding, engine building. Can't seem to quit #-o
jsgarage
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Re: 1990 Ford 4.0 oil pressure

Post by jsgarage »

Crate, I had a SBC Z-28 that did that (in a used car). On teardown, I found one cam bearing that was absolutely roached although the stock cam was fine as was the oil pump. A friend that races these things said that was a sure sign the engine was overheated at some point. As was said, check your bearing clearances and be sure to include the cam bearings!
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