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Old 01-26-2003, 12:33 PM
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Small chevy, Dialy driven, Big cam, Intake, Carb, Headers, Exhuast, The usuall stuff. I've noticed after 3 years of service that the oil pressure will stay steady at 40 pounds at cruising and fall slightly to 35 while under load such as a hill or light acceleration. Then Increase while coasting to 40 pounds down the same hill in front of my house. The problem is more exaggerated after I exit the highway and the oil temps are a little warm. Almost non existant while the engine is still cold first thing in the morning.

What do you think? I'm partial to worn rod and mian bearings.

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Old 01-26-2003, 01:51 PM
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your problem usuley comes from worn thrust main bearings, is vech. auto or standard? autos dont normanly wear mains thrust surface. only cure is replace bearings and crank. good luck
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Old 01-26-2003, 02:14 PM
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5 speed to be exact.
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Old 01-26-2003, 07:10 PM
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Completely normal, the phenomena you have just described is load induced pressure loss and it typically happens on engines with looser clearances than new. As the engine gets loaded the bearings will actually pump more oil out of the clearance space leading to a slight reduction in oil pressure on the gauge.

Don't worry about it until it drops 15 pds or more under load, then it's serious wear.
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Old 01-26-2003, 07:33 PM
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Sounds like main bearings to me, nothing to really worry about yet though. At cruising/idle, the engine has high vacuum acting on the pistons which holds the crank up in it's bores against the oil feeds (oil pressure reads normal). Under load, there's less vacuum acting on the pistons (and more force trying to push the crank down), allowing the crank to settle in it's bores away from the oil feeds. This allows more oil to escape creating less pressure. If the pressure actually increases during decelleration, I would be a little more concerned with the bearings.
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Old 01-27-2003, 06:40 AM
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I'm not used to running these small chevy oil pumps stock. I know it's only rated at 30 pounds and 15 at idle at normal temps but they make me a little nervous anyway. This motor already spun two bearings before and I just keep wiating for it to happen agian. I haven't torn into the motor yet. I'm gonna wait untill the new shop goes up in the backyard. (30x40, 20 foot ceilings and a floor lift). I guess it'll last that long.
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