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Old 01-29-2011, 12:12 AM
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80+ psi oil pressure: Harmful?

Long story short I bought a new (to me) '88 Scottsdale, 6" lift, 35's, Dana 60's front/rear, with a 472 big block caddy motor in it. It was -20 degrees below zero when I started it to drive it home after I bought it, so I wasn't concerned with the high oil pressure, but once it warmed up (195*F) The oil pressure dropped to about 70 psi at idle, but with even the slightest nudge of the throttle it would peg past 80psi on the gauge.(80psi is max on the gauge) Tomorrow I'll test it with another gauge, but if it's not the gauge I was expecting the pressure relief valve(spring) in the oil pump it's self.

I was wondering if running it at high oil pressures (probably well above 80psi) will or already did hurt anything?

The guy (supposedly) put 9:1cr pistons in it, a little hotter cam, and bored it out 20 over, dual exhaust, and other minor mods , but he didn't mention any high volume/pressure oil pump though...

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Old 01-29-2011, 04:06 AM
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Quote:
Originally Posted by QParker
Long story short I bought a new (to me) '88 Scottsdale, 6" lift, 35's, Dana 60's front/rear, with a 472 big block caddy motor in it. It was -20 degrees below zero when I started it to drive it home after I bought it, so I wasn't concerned with the high oil pressure, but once it warmed up (195*F) The oil pressure dropped to about 70 psi at idle, but with even the slightest nudge of the throttle it would peg past 80psi on the gauge.(80psi is max on the gauge) Tomorrow I'll test it with another gauge, but if it's not the gauge I was expecting the pressure relief valve(spring) in the oil pump it's self.

I was wondering if running it at high oil pressures (probably well above 80psi) will or already did hurt anything?

The guy (supposedly) put 9:1cr pistons in it, a little hotter cam, and bored it out 20 over, dual exhaust, and other minor mods , but he didn't mention any high volume/pressure oil pump though...
Only thing I would worry about is blowing the oil filter off if you rev it up cold.
I had a buddy in the service that had a radical small block in the front end of a corvair with crazy (100lbs cold) of pressure and couldn't hardly touch the gas till the engine warmed up to operating temperature and dropped down to 80 at idle. Red line on his engine was 7,500 rpm. Old rule of thumb is 10 lbs of pressure for every 1,000rpm. At 80 lbs, you have more than enough and is probably robbing your engine of power trying to pump that much pressure.

What wt oil are you using? At -20* I hope it's like 5w-30.
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Old 01-29-2011, 05:58 AM
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The first it will do is blow the oil filter gasket out. That does seem a little high. If the gasket came while you were driving down the road you could have major problems in a short time.
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Old 01-29-2011, 06:00 AM
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Not to mention causeing a rear main seal seep/leak...
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Old 01-29-2011, 06:04 AM
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What weight oil is in it? Hopefully not 50w !!!
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Old 01-29-2011, 06:22 AM
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Anything higher than 60-65 is going to cause excessive load on the pump drive shaft, blow the filter or gasket out, and cause rear main leaks.
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Old 01-29-2011, 07:38 AM
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My first guess would be a bad sending unit or gauge. Its unusual to get pressures that high with any common oil pump they might have used. Most rebuilders do not recommend high volume pumps with an SBC, since they do not need it.

Get a cheap mechanical gauge at the parts store and connect the line into the fitting where the sending unit is screwed in. Once you verify the real pressure, you will have a better idea of whether something needs to be fixed.

Bruce
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Old 01-29-2011, 08:24 AM
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To get >80psi I would think two things would have to occur at the same time:
1. Bad pump pressure relief valve or >80psi press rel valve spring (not typical).
plus
2. Excessive flow restriction from tight clearances, galley trash,or heavy oil.

I like pump that hits pressure relief on cold start up and operates below pressure relief warm.

I would triple check pressure as others said.

If pressure is really over 80psi I would have a looksee to verify right front rocker is getting oil.
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Old 01-29-2011, 10:43 AM
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I know for a fact that the oil pressure on a sbc is 80psi when you first start, and after warming up it drops down to 35psi idle, and 65psi when you bring the rpm up. This when you are using a high pressure, low volume oil pump. You either have high pressure, high volume oil pump. or the clearance on the bearings are very tight or both. the only thing is going to happen is blow the oil filter. That is what happen to a buddy of mine in his 340 Duster.
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Old 01-29-2011, 12:13 PM
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When I got it home I changed the oil to 5w30, so that should be fine, I'm in the process of checking it with a new gauge.

FWIW, It's a 472 big block cadillac, not a sbc.
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Old 01-29-2011, 12:16 PM
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I'm gonna go with the sender or gage as well.

I've had to replace both on my 79----but that truck has 400,000 miles on it.

Kinda weird to be driving down the hiway and notice ZERO oil pressure

Turned out that instance was just the sender.

I figured after 20 miles and no noise, I was okay till I got the sender replaced
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Old 01-29-2011, 12:20 PM
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I'm glad mine is high, not 0. I wouldn't have driven it if it read zero on the gauge.
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Old 01-29-2011, 12:30 PM
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Quote:
Originally Posted by QParker
When I got it home I changed the oil to 5w30, so that should be fine, I'm in the process of checking it with a new gauge.

FWIW, It's a 472 big block cadillac, not a sbc.
I Know its a caddy engine. I should of mention what ever a typical engine is with the engine oil pressure. Sorry
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Old 01-29-2011, 12:51 PM
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anybody know where to hook up a manual oil pressure fitting to the block on a 70's 472 bbcaddy?
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Old 01-29-2011, 01:02 PM
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Quote:
Originally Posted by QParker
Long story short I bought a new (to me) '88 Scottsdale, 6" lift, 35's, Dana 60's front/rear, with a 472 big block caddy motor in it. It was -20 degrees below zero when I started it to drive it home after I bought it, so I wasn't concerned with the high oil pressure, but once it warmed up (195*F) The oil pressure dropped to about 70 psi at idle, but with even the slightest nudge of the throttle it would peg past 80psi on the gauge.(80psi is max on the gauge) Tomorrow I'll test it with another gauge, but if it's not the gauge I was expecting the pressure relief valve(spring) in the oil pump it's self.

I was wondering if running it at high oil pressures (probably well above 80psi) will or already did hurt anything?

The guy (supposedly) put 9:1cr pistons in it, a little hotter cam, and bored it out 20 over, dual exhaust, and other minor mods , but he didn't mention any high volume/pressure oil pump though...
This is probably telling you that at a negative 22 degrees, the oil is so thick that it can't get out of the bypass faster than the the pump is putting it in. That's not to say there isn't a high volume pump in there, only to throw a lasso around the reasons you're seeing what your're seeing.

You might try a thinner oil, thought at -22 degrees the engine really ought to be hanging on a heater when it isn't running.



Bogie
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