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Re: [Tigers] Oil Pressure

To: Dave Munroe <dave@munroe.ca>
Subject: Re: [Tigers] Oil Pressure
From: drmayf <drmayf@mayfco.com>
Date: Mon, 02 Aug 2010 10:12:46 -0700
Dave,  several things come to mind.  One is, of course, the in dash 
pressure gauge.   See if you can rig up a second gauge for a direct 
comparison. But, there are other issues as well. If you have the stock 
remote oil filter setup, then the adapter at the block receives the oil 
and makes a hard right turn headed to the filter.  It must pass the hose 
to adapter fitting, the solid part of the hose to "rubber" hose 
connecion twice and then flow though another hose fiting at the filter 
adaper and then make another hard turn going into the  filter proper. 
Ther filter to engine comes straight out of the filter through a 
fitting, then through the similar hose, with its losses, then into the 
block adapter.  So, there are a number of places where the flow can be 
reduced.  reducing the flow on the down stream side reduces the 
pressure.  Also, did the dyno shop drain the oil and you put in a 
different viscosity? If so, that will change the flow and pressure 
also.  Did you use the same oil brand and weight?   When they had the 
engine on the dyno, how big was the mechanical gauge pressure line or 
was it screwed directly into the engine?  The dinky oil pressure line 
that runs to the dash gauge can cause some pressure losses.    It would 
have been interesting if the shop had used your remote filter set up on 
the dyno. Why didn't they?

just some things to think about...

mayf

Dave Munroe wrote:

> Ok guys, the mystery continues.
>
> I have sought advice here about oil pressure and we have discussed 
> this before. But now more intelligence has been gathered.
>
> My engine was built by a well meaning but as it turns out, 
> inexperienced Brit mechanic in 2005. Amongst more serious problems,
> my engine's oil pressure also was below what I have come to believe is 
> "normal" pressure for a fresh, quality re-build.(50 to 55 psi cold, 40 
> to 50 psi hot with 10-30W oil). I was tired of, and concerned with, 
> the O.P. gauge showing the needle far to far to the left of center.
>
> I had my engine removed and "blue-printed" by a knowledgeable and 
> highly regarded local shop. They found and corrected the other, more 
> serious problems, and when reassembled, put it on their shop dyno. 
> During the rebuild they installed a new, standard oil pump on the 
> recommendation of many on this list who responded to my earlier 
> inquiries, to replace the high volume pump that I had installed in the 
> first re-build.They also installed a large filter directly on the 
> block for the several pulls the engine went through on the dyno. They 
> had hooked-up a mechanical oil pressure guage and a transducer that 
> fed into their diagnostic computer. My engine was showing 70 psi at 
> 1500 rpm, and it rose to 75 at 5500 rpm (redline).
>
> Back in the car with the remote oil filter set-up, with new, large 
> diameter hoses fitted, it shows 45 psi cold, and 25-30 hot at 3,000 to 
> 4,000 rpm. I am at a loss to understand how the remote filter set-up 
> could possibly cause this drop in indicated pressure. The only other 
> variable is my pressure gauge, which is nothing if not consistent.
>
> I will appreciate any wisdom or suggestions as to what is going on and 
> how to correct this low pressure problem.
>
> Thanks for your help,
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