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Re: pardon my ignorance...

Subject: Re: pardon my ignorance...
From: (Denise Thorpe)
Date: Mon, 10 Jun 96 11:24:33 PDT
Will Zehring asked:

> Fellow fiends:
> I am catching up on the digests (I've been out of town) and read the posting 
> regarding fluctuating oil preasure and have grown confused.  
> --How can the gauge be reading 90lbs if the engine has a 60 lb oil preasure 
> relief valve?  Doesn't the valve open at 60 lbs and therefore establish an 
> maximum upper oil preasure at about 60 lbs?
> While it is always better to have oil preasure than to not have it:
> --why was the engine designed and built with a 60 lb oil preasure relief 
> valve if it can run happily and safely at 90 lbs?  
> --might not some high preasure gasket seals (head gasket) be stressed with 
> 90 lbs of oil preasure?
> --What are the chances the oil gauge is the problem?  Might not the fellow's 
> needle be loose and the indicated preasure is not the true preasure?  Or... 
> is the fellow's engine's relief valve not functioning properly?  Did you 
> install an "uprated" spring in the valve assy?
> Or, am I completely missing the point (again)?
> Will Zehring

Dunno.  But I knew someone who modified their oil pump for increased pickup
('55 MGA, it was #255 or so) and ended up with 90 lbs of pressure.  The 
head gasket didn't leak, but the back of the gauge did spraying oil all over 
the carpeting.  My daily driver '66 B has the same modification (made by a 
die grinder, or Dremel tool, as you guys like to call them) but to a much 
lesser extent.  My car has 80 lbs of pressure and no leaks yet--at least no 
leaks from excess pressure.  The engine didn't leak at all for the first 60K 
miles or so.  Now that I'm building all these engines (two) I'm tempted to 
pull the pan off my daily driver and look at the pump so I know how it's 
done--I forgot--but then my car would no longer be a driver.

In answer to your previous question, Will, oil takes the path of least 
resistance.  Glad I could help.

Speaking of gauges, I was once told that the combo oil pressure and temp 
gauge is called a safety gauge and it was designed so that the two needles 
would form a vertical line when everything was as it should be.  This is 
so that the driver can verify the condition of the car at a glance.  If you 
look at the gauge, this is about 55-60 lbs of oil pressure and 180 degrees 
F.  My car has a 160 degree thermostat and the modified oil pump, so the 
needles in my gauge form a slightly offset line about ten degrees clockwise 
from vertical.  Anything else upsets me.

Denise Thorpe

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