SBC Oil Pressure Problem....!!?? - Hot Rod Forum : Hotrodders Bulletin Board
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Old 07-23-2005, 09:34 PM
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SBC Oil Pressure Problem....!!??

Heres the story. I installed a 1987 and up roller set up in a 1969 block. I had the machine shop drill and tap into the center oil canal of the block in order to install this setup. When I built the engine, I used a new crank, all new bearings, I plastigauged every bearing and they all were all between .002 and .003 of clearance. I installed a new high volume oil pump.

For some reason, when the engine gets to operating temp, the oil pressure drops to about 10psi when idling. When driving it goes to about 35-40psi. This is a bit lower than what im use to. When the rpm is brought up to 4000 to 5000, The oil pressure maybe hits 43psi. Im use to idleing at 25-30psi and running at 45-60psi. Could the oil be seeping throught the bolts that go into the oil canal? Thats the only thing I can think. Can anyone recommend a good thread sealant? I already pulled the pan off and installed another new oil pump, but the same thing happens. The only other thing I can think of is maybe the mechanical oil gauge is reading wrong? Is that possible? Any info will help. Thanks.

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Old 07-23-2005, 10:45 PM
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When did this start happening, recently? Just checking since you're saying you're used to idling 25-30psi and running 45-60psi. It wouldn't hurt to check the oil guage but I'm not sure what test to do. Hopefully someone more experienced will come in and help you out more .
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Old 07-23-2005, 11:19 PM
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SBC's are notorious for their crazy low oil pressure, yet it doesn't really affect them at all. It could be a problem somewhere but if all your clearances are in check i wouldnt worry about it too much
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Old 07-24-2005, 04:03 PM
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With that same engine, before when it was a 350, is what I am talking about. Also all the other engines I have built had the same higher oil pressure. Im thinking the oil pressure in the block is pushing through the threads of the 3 bolts holding the roller setup down. Could this be possible???
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Old 07-24-2005, 05:00 PM
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My truck has about 10 psi at idle as well but it's been like that for a while now. It bothered me at first but there really is no load on the engine at idle anyway. If your oil pressure comes up quickly with your engine speed I wouldnt worry about it. There will be a point where the pressure will not rise any higher because if the relief inside the pump. Maybe thats why you say it never goes above 43 psi. Any of the high volume pumps Ive ever used come with a different spring (lighter or stiffer) to raise or lower the relief point.
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Old 07-24-2005, 05:09 PM
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your numbers are fine, watch for a decrease, otherwise don't worry yourself.

K
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Old 07-25-2005, 11:45 AM
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I had the identical problem recently with my BB chevy. It turned out that the guy who sold us the main bearings gave us standard sized instead of the .010" oversize that we asked for. We wasted a lot of time , work and fuel before we found that out. You might want to pull the oil pan and recheck a main or two unless you know for sure that they are correct. Another possibility may be a missing galley plug in the front of the block under the timing cover.
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Old 07-25-2005, 02:14 PM
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ChevyElC81
I think lots of answers have come that didn't address your first question. So, if you have a high pressure/high volume pump, and the screws have not fallen completely out of their holes, I'd say the retaining screws are definitely not the cause.

Did you put in the high pressure pump spring?? Is the pump a high volume pump, or simply high pressure? If you install a standard volume pump, and do not install the high pressure relief spring, and have a small error in your gauge, it'd be pretty natural to see the pressures you are seeing.

Pat
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Old 07-25-2005, 04:40 PM
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Master fixer

If you had the block hot-tanked on this build-Your machinest may have removed the oil galley plug thats located under the rear main cap -this is the main feed outlet for the oiling system. If the plug is missing, the oil is bypassing back to the pan, missing the filter as well even at higher RPM's. Stick a small shank screwdriver in the hole and if it goes in more than 3" the plug is gone. This is a rare condition but has the same symptoms you are having. You can see the plug with a flashlite if there is room to look. Good luck!!!
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