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Old 09-12-2007, 11:15 PM
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Oil Pressure Problem

I have just rebuilt a 350 SBC and have a prob with the oil pressure, at 2000 RPM it used to run at 40 psi now when it's hot it runs at 30 psi at the same revs but if you take your foot off the gas the pressure increases to 40, I can vary the oil pressure up and down with the throttle when I'm coasting at 2000 rpm. Has anyone got any ideas?

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Old 09-13-2007, 12:20 AM
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Welcome to Hotrodders Rust. Being you didn`t say if you have a electrical gauge or mechanical gauge, all I can say is if electrical, check and clean the sending unit. How old is the gauge? If mechanical, how much air does it have in the line? It really don`t sound like it has a oil pressure problem it`s just tending to move around more than you perfer.
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Old 09-13-2007, 03:31 AM
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Preessure Gauge

It is a mechanical gauge, and I have bled the air from the line
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Old 09-13-2007, 05:55 AM
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If you built it with a no bypass filter adapter try a new oil filter, if the block wasnt cleaned real well after machining it wont take long to clog the filter.

Larry
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Old 09-13-2007, 06:01 AM
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Quote:
Originally Posted by rustrodder
I have just rebuilt a 350 SBC and have a prob with the oil pressure, at 2000 RPM it used to run at 40 psi now when it's hot it runs at 30 psi at the same revs but if you take your foot off the gas the pressure increases to 40, I can vary the oil pressure up and down with the throttle when I'm coasting at 2000 rpm. Has anyone got any ideas?
Hi, if you know your engine clearance's are all correct, and you ruled out air in your gauge line, i would guess that your pump pickup tube could be loose, sucking air, or the tube is to far off the bottom of the pan. I like to see the pickup 3/8 off the bottom. good luck sam-missle
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Old 09-13-2007, 04:20 PM
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Filter

I,ll change the oil filter today and post the result
Thank you
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Old 09-13-2007, 06:39 PM
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I don't think air in the pressure guage line will be a problem. Pressure is pressure, whether it's full of oil or air.
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Old 09-14-2007, 12:55 AM
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I have just put on a new oil filter and the problem is still there.
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Old 09-16-2007, 10:41 AM
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pressure is pressure, yes, but air will compress under pressure. Oil will not.
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Old 09-16-2007, 01:54 PM
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I've never had problems because of air in my oil pressure line, it seems to work the same either way.

When you say you can vary the oil pressure with the gas peddle, does the oil pressure seem like its connected to the acceleration of the vehicle? if the pickup is cracked it could be the oil is sloshing away from it and exposing air.
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Old 09-19-2007, 11:25 AM
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Oil pressure problems

I had a similar problem on a 415 sbc stroker I built, with some help from this forum it turned out to be to much oil in the pan. I run 6 1/2 quarts in a 7 quart pan and my oil pressure problems went away. Turns out the crank was foaming the idle I would loose pressure about 3000 rpms and as soon as I let off the pressure would go up. Might be worth a shot.
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