302 oil pressure

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Apr 21, 2008 | 08:41 PM

Mick1930

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Joined: Dec 2007

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From: MA.

302 oil pressure

<TABLE id=HB_Mail_Container height="100%" cellSpacing=0 cellPadding=0 width="100%" border=0 UNSELECTABLE="on"><TBODY><TR height="100%" width="100%" UNSELECTABLE="on"><TD id=HB_Focus_Element vAlign=top width="100%" background="" height=250 UNSELECTABLE="off">I have a used unknown milage 302 in my 56. I is very clean and looks great..but when it starts the oil pressure fluctuates. Get the revs up at it goes to 40psi and if I let it idle it goes down to 25. My other car is a newer model and the oil pressure guage always stays in the middle normal range.
So can some of you please give me some of what you see in these old motors.
Runs fine though..not taken it on the highway , just around the block.
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Apr 21, 2008 | 09:00 PM

eman92082

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From: Valley Center, California

25PSI at Idle and 40PSI above Idle is perfectly fine and normal. What you are seeing is the actual pressure with the old gauge.

New car gauges are electronic and buffered to death. They don't really discriminate much between low or high pressure. They look the part, but they aren't much better than a dummy-light. You either have pressure or you don't.

Apr 21, 2008 | 09:11 PM

Mick1930

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From: MA.

Thanks E-man,
What would you expect at hot idle?
This is a used 302 and it is all pretty and painted..just do not know any history as it was in the 56 when purchased.
But as long as I see pressure and it fluctuates..no problemo?
The guage is a new chepo one from Autoparts it has the clear tube running from the engine..lots of air little oil in there..

Apr 21, 2008 | 09:47 PM

sparky

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From: Comox Valley, Canada

In order to read accurate you will have to get rid of the air, it will act like a shock absorber sort of and give fluctuations and incorrect readings.........just loosen the nut at the guage with the engine running the air will bleed out.....ps wont hurt to have a rag handy and do not loosen the nut more than necessary to let the air escape.

Apr 21, 2008 | 10:04 PM

eman92082

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Joined: Apr 2007

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From: Valley Center, California

Yeah - The fluctuation you see is just a result of the Oil Pump rotating speed in the lower RPM range. You really see it when you have the wet line to the Gauge.

I should mention that there's nothing wrong with electronic senders from companies like AutoMeter or Stewart Warner etc. I was referring to the gauges that the factory installs like in my 2000 Lariat. Low Idle or freeway, hot or cold, the gauge just sits at 3/4 and never moves except on start-up.

You'll get a lot of opinions about what oil pressure should be. If the engine is stock and driven reasonably you should be OK. The hot pressure will probably drop 10 PSI or so. Your oil viscosity, engine clearances and relief spring have a lot to do with the result.

Apr 21, 2008 | 10:07 PM

eman92082

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From: Valley Center, California

Sparky is right also. I assumed you were referring to fluctuation with engine RPM. If the needle is bouncing around that's another issue.

Apr 22, 2008 | 01:12 AM

Sandidande

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Joined: Jul 2006

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From: La Mesa (East San Diego)

Hi Again Mike,

If you are getting those readings that's actually pretty good. My 390FE with a Melling High Volume (not high pressure) might get up to 40 cold then settles to 30 to 35 hot. It idles at 22-25 hot at 600 rpm. And I've only got 2000 miles on the engine.