oil pressure! motor new, start up 75 lbs ! now1lbs at1400 rpm - Hot Rod Forum : Hotrodders Bulletin Board
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Old 02-23-2004, 09:20 PM
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oil pressure! motor new, start up 75 lbs ! now1lbs at1400 rpm

please help! pro built 355 small block. mellings hi volume oil pump. at start up ran at 2500 rpm for 30 minutes for cam break in. oil pressure stayed at 65 to 75 psi throughout. engine temp never over 170 degrees. retourqued intake, heads, and run valve lash, changed oil and filter and added oil cooler and adapter for cooler lines. started back up had leak at adapter, turned off engine. took adapter and cooler off. restarted engine and oil pressure was at 35 psi at 2500 rpm. at idle pressure drop to1 to 2 psi. check oil psi gauge, oil level ect. removed valve covers, started engine and at idle oil pressure remained at 1 to 2 psi. oil very slow and weak comming to rocker arms. shut engine down. dont know if complete info on engine is needed, everything is new. thank you for your time. im at my whits end. do not want to pull engine unless you all think it nessary.

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Old 02-24-2004, 12:49 AM
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First off, I would get a direct screw in gauge and read it at the front oil gallery outlet at the front of the block and see what it says, most oil gauges are not accurate below 10psi, some as high as 15 psi. my cutlass has a sbc and a high volume oil pump, after it gets hot the gauge reads zero psi oil pressure, you have to take into account, hot oil is thinner, and at this low of pressure it`s passing through the oil filter, which slows it down more, and the cam is what`s driving the oil pump which runs at half the crank speed, so if the engine idles at 650 RPM the oil pump is only turning 325 RPM. another thing you can do is remove the oil pressure sending unit and check it for trash, we had did a rebuild on a friends sbc, sometimes it read it had great oil pressure, other times it would read zero and never move, we cleaned the sending unit and solved the problem. If the engine doesn`t have any kind of death knocks or rattles at idle, I wouldn`t worry about it, normal oil pressure is usually 10 psi per 1000 RPM.
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Old 02-24-2004, 06:57 PM
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Could your oil pickup be clogged from the break in lube you used? Was it a new pickup? Did you clean it if it was used?
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Old 02-26-2004, 08:01 PM
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10 psi per 1000 is at max rpms not 10 psi at 1000 etc. ie 6000 rpms=60 psi safe. cut filter open and check for filings and that will tell u whats going on. I can peg a gauge with a speed handle, so something is wrong.
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Old 02-28-2004, 07:24 AM
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Kind of a longshot....but a broken or jambed up pressure relief spring or valve in the oil pump. I had a Buick 400in that suddenly had no oil pressure at idle but did get decent pressure at 2000rpm or above. Turned out to be a nylon tooth from the cam gear had wedged in the pressure relief valve and was hanging it open.
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Old 02-29-2004, 07:19 AM
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My question is was the pump primed properly before being installed in the engine? Also a high volume pump will suck a stock oil pan dry before the oil has a chance to drain back down and if this is the case you'll either need to change to a different oil pan or change pumps. Either way 1lb of oil pressure is too scary to me and could eventually wipe out the bottom end, I'm not used to anything under 30lbs. at idle warm.
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Old 02-29-2004, 12:54 PM
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Do you have a plastic line going to your guage?If so make sure line is not crimped somewhere.
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