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Old 06-03-2010, 11:15 AM
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oil psi scare

ive got new motor put together using a melling 10552 oil pump. supposed to be 10% more volume. it holds 50 psi cold and after i drove it for a few minutes at operating temp. 180 degrees, it only gets 20 psi idling in neutral and about 12 psi in gear. but when i rev it up it goes back to 50 psi. i also have a screen type windage tray in the motor. is this anything to be worried about?

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Old 06-03-2010, 11:18 AM
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i would worry about the 12psi in gear, if it were 15-20 psi in gear that would be okay (still slightly low but not bad) but not 12psi. who built the motor, did you get a spec sheet, what where the bearing tolerances
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Old 06-03-2010, 12:32 PM
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i built the motor, the bearing clearances are stock, about .00025. i went back out and checked it again and now with the idle at 850 rpm it is 20 -23 psi and in gear about 15 to 18 psi. but as soon as i tap the throttle it goes to 35 psi and about 50-60 psi above 2000 rpm. i haven't got the motor completely tuned and at 500-600 rpm in gear with a slight miss is when it is 12 psi. im thinking about going to a heavier oil 20/50, im using 10/40 now.
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Old 06-03-2010, 12:47 PM
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10/40 should be fine, and i think you ment .0025". even on a stock engine i wouldn't have it idling in gear at less than 600rpm and at 15psi you are fine, general rule of thumb when it comes to oil pressure is that you want the psi to be 10lbs higher than the rpm you are running. i'll have to expain cause that does sound a little wierd.

say you are idling in nuetral at 850rpm then you want atleast 18-19psi, if you are idling in gear at 600rpm then you want ateast 16psi, say you are cruising on the highway at 2700rpm then you will want atleast 37psi. you get the idea now. now say that you motor wont reach over 55-60psi then i wouldn't run it past 5000rpm, but if you can get 70psi out of it then i would feel safe turning about 6000-6200rpm
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Old 06-03-2010, 01:04 PM
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i remember reading for 1000 rpm i need atleast 10 psi. if so i should be ok. i havent really checked it above 6000rpm though.
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Old 06-03-2010, 02:15 PM
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Quote:
Originally Posted by runn141
i remember reading for 1000 rpm i need atleast 10 psi. if so i should be ok. i havent really checked it above 6000rpm though.

i wouldn't go by that, i would want atleast 15-18psi at the least at 1000rpm
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Old 06-03-2010, 02:30 PM
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Quote:
Originally Posted by my87Z
i wouldn't go by that, i would want atleast 15-18psi at the least at 1000rpm
so far it is 20 to 25 psi at idle hot and 15 to 18 in gear. im just gonna drive it, if it blows it blows. if so ill just eat the $4500 and get out of this hobby.LOL
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Old 06-03-2010, 02:49 PM
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Quote:
Originally Posted by runn141
so far it is 20 to 25 psi at idle hot and 15 to 18 in gear. im just gonna drive it, if it blows it blows. if so ill just eat the $4500 and get out of this hobby.LOL

as long as you are above 15 psi at idle in gear and it's idling around 600rpm in gear then you are fine. i wouldn't worry about it
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Old 06-03-2010, 03:19 PM
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Quote:
Originally Posted by my87Z
as long as you are above 15 psi at idle in gear and it's idling around 600rpm in gear then you are fine. i wouldn't worry about it
thats about what it is at. I thank you or your help.
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Old 06-03-2010, 03:51 PM
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What brand oil filter are you running.
Its sounds like loose bearings to be honest.
The numbers you posted are not awful but not what I would expect from a fresh engine.
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Old 06-03-2010, 04:32 PM
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I wouldn't worry about it unless it gets worse, I had a street/strip 406 that idles at 10-15 psi hot, it lasted for 10 years and was still fine when I pulled it apart to go faster. As long as the pressure comes up as soon as you raise the rpm from idle you will be fine.

Just for reference, the stock oil pressure light sender Chevy uses comes on at 4-7 psi.
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Old 06-03-2010, 04:46 PM
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Quote:
Originally Posted by T-bucket23
What brand oil filter are you running.
Its sounds like loose bearings to be honest.
The numbers you posted are not awful but not what I would expect from a fresh engine.
fram oil filter
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Old 06-03-2010, 04:48 PM
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Quote:
Originally Posted by T-bucket23
What brand oil filter are you running.
Its sounds like loose bearings to be honest.
The numbers you posted are not awful but not what I would expect from a fresh engine.
since it is summer time, im gonna change to 20/50 just to see if there is any change.
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Old 06-03-2010, 11:27 PM
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Your oil pressure is fine. My 03 Dodge Ram with a Hemi idles hot around 4-8lbs. stock. But at speed, it's 60-70lbs.... crazy.

Ditch the Fram Extra Guard (unles you are doing really short oil change intervals - 3K or less) and get a filter with a anti-drain back valve.

I would stick with the 10/40 unless you are in a 'hot climate'. The 20/50 in my 327 with .0025 on the rods and .0020 on the mains didn't bump up my hot idle much, maybe 1-2 psi. And for that matter it didn't effect WOT runs much either, maybe 2-3psi. It REALLY bumped oil pressure when cold, which I didn't find desirable.
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Old 06-03-2010, 11:40 PM
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I've used and liked Wix since I was a kid.
http://www.wixfilters.com/wheretobuy/index.asp
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