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Old 08-27-2006, 05:58 PM
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sbc oil pressure problem

today when driving the car i noticed a very strange problem,, normal pressure is 30-35 at idle rising to 60-65 at 3000 and above.. today while just cruising along i noticed that the pressure was down around 30 psi at 3500.. when i backed of to 3000 the pressure went up to 45.. i am using good oil and it is clean,, the bypass is blocked and the filter has been on the motor less than 700 miles.. what is happening

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Old 08-28-2006, 09:41 AM
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any one have any thoughts on this
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Old 08-28-2006, 10:55 AM
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What filter?

Did you check the oil level?
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Old 08-28-2006, 11:15 AM
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Sounds like to pick up fell out of the pump. I would check the oil first though. It could just be very low.
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Old 08-28-2006, 02:43 PM
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moroso racing filter,, oil level is good , 10 qts.. took sump down and everything appears ok, pickup is still on the pump, pulled rear main and it looks perfect, same with rod bearings ... ran it for an hour this morning and it would not do it again,, pressure was normal, 7o cold at idle, 40 idle hot rising as soon as i rev thew engine.. what is going on
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Old 09-03-2006, 02:30 PM
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took the car out this morning and it did it again,, have decided on a new oil pump and a system one oil filter,, come on guys someone must have some ideas about this,,, george
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Old 09-03-2006, 03:05 PM
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What kind of gauge(s) do you have? If it electric, does your voltage reading change at the same time? Just a thought.

what oil pump are you using? High volume?
Could it be filling the heads at high RPMS and the return holes can't keep up?

Does the oil pressure stay low if you rev it higher?


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Old 09-03-2006, 03:13 PM
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40 psi hot idle is really high. Almost every SBC I've owned has run around 10 to 15 psi at a hot idle. Sounds like you have a high pressure pump. I don't think you have anything to worry about as long as pressure increases with rpm. But as stated earlier you may be pumping your pan dry thats all a high pressure pump is good for on a street car. IMHO.
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Old 09-03-2006, 03:15 PM
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sticking pressure relief valve, only at times when RPM drops. Also rare but possible, a piece of trash (bolt/nut/stone/hard jb weld) moving around in an oil passage. How did you plug the bypass?

I had a bad oil pressure and temp gages last week from europe some place. Auto meters solved my oil pressure and temp problems.
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Old 09-03-2006, 06:03 PM
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oil pump is high volume pump,, pressure gauge is a mechanical autometer unit,, problem occurs at around 3500rpm which is fairly low and increases pressure if i bring the rpm down a little,, i have checked everything i can think of , bearings are good pump looks ok , pickup is welded on.. i built this engine 2 yrs ago and it has been fine to now ,, problem started suddenly, it was ok one day and the following day was giving problems,, have done no work on the motor that could in any way cause this to happen,, by the way the bypass is blocked with an after market part and i am using a 7 qt sump and an accusump to prevent oil starvation at high rpm..thanks for giving my problem some thought
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Old 09-03-2006, 08:52 PM
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I have had lot of different engines. It is what happens to you when you are 60 years old. Most have been race engines. I've seen a lot of freeky stuff.

What about trash in the pan like pieces of silicone or something about the size of a quarter, big enough to partially block the oil pickup when the pump is sucking enough oil to bring it up to the inlet but heavy enough that it falls away whenever the RPM drops. This would fit your symptoms.


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Originally Posted by zephyrc
oil pump is high volume pump,, pressure gauge is a mechanical autometer unit,, problem occurs at around 3500rpm which is fairly low and increases pressure if i bring the rpm down a little,, i have checked everything i can think of , bearings are good pump looks ok , pickup is welded on.. i built this engine 2 yrs ago and it has been fine to now ,, problem started suddenly, it was ok one day and the following day was giving problems,, have done no work on the motor that could in any way cause this to happen,, by the way the bypass is blocked with an after market part and i am using a 7 qt sump and an accusump to prevent oil starvation at high rpm..thanks for giving my problem some thought
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Old 09-03-2006, 09:10 PM
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i know this probably dont help but sb chevys are safe at 7 psi. are you using oil restrictors? might not be letting oil return fast enough.
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Old 09-03-2006, 11:14 PM
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He has a huge pan and large oil supply. If his valve covers were filling up there would be evidence of pressureization of the valve guides which would cause it to smoke pretty bad.

Quote:
Originally Posted by runn141
i know this probably dont help but sb chevys are safe at 7 psi. are you using oil restrictors? might not be letting oil return fast enough.
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Old 09-04-2006, 07:44 AM
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Did you try another filter?
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Old 09-04-2006, 11:58 AM
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Quote:
Originally Posted by Bob147
Did you try another filter?
yes, i changed the filter twice, they were all moroso racing filters, i have ordered a system1 oil filter now just in case it is the filter quality.. how far below the crank should the oil level be in the pan
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