oil pumps (not efi)

[tom cloud]

Coupla things:

 1 - I've just found another area where you can mark me dummy:
to wit, the reason the oil pressure in my truck has remained constant
for five years and 107,000 ++ miles is that the 'gauge' is really
just a switch that moves the pointer to the same place regardless
of the pressure.  I thought the oil system in my truck was pretty
remarkable -- now I know why!  ANY OF YOU FORD GUYS OUT THERE ??? 
You can tell corporate for me that I am some ticked!!!  If I'd wanted
an idiot light, I'd passed on the "gauges".  I feel like I got
cheated ... no, I *KNOW* I got cheated.  I ordered gauges and I got
an on / off indicator.  A light would have been better.  And what'd
Ford save?  They still had to have the gauge (and that probably only
costs a coupla bucks), all the wiring is there, so the price savings,
if any, is simply the diff between the cost of the pressure switch and
a pressure sensor -- couldn't be much.  If they'll do that, wonder
what other wonderful surprises I have yet to discover?

 2 -  regarding Darrell Norquay <dnorquay at iul-ccs.com>'s reply, below,
it is my understanding that the oil pump has a pressure relief or control
bleeder (I don't have one here in front of me, but I'm pretty sure of
that).  If so, the volume the pump can deliver is not necessarily the
volume it will deliver.  It will pump oil against the engine until the
pressure builds to the pre-set limit and then the bypass will divert
the unused oil back into the pan or into the pump's intake (dunno which).
Ergo, the pressure stays the same and the volume is no more than a stock
pump's, assuming that the stock pump could maintain the same pressure.
Course, if there are sloppy tolerances, etc, the hi-vol pump would come
nearer keeping the pressure at the desired level than the stock -- least
that's how I understand it.

>At 07:20 AM 12/11/96 -0600, Tom Cloud wrote:
>
>>The high volume pump does not increase pressure, so no more oil
>>flows through the engine than for a normal pump, unless there's
>>a loose fitting or such, right?
>
>A high volume pump will, in fact, increase oil pressure in most cases. I say
>in most cases since if bearing clearances are loose, it may not increase
>pressure over stock, but it will have higher pressure over a stock pump,
>which would be below normal in this case.  This is a band-aid solution,
>however, if the engine has proper clearances, the high volume pump will not
>be necessary.
>
>> - same volume of oil will be pumped by stock and hi-vol pump (i.e.
>>hi-vol pump will just recirculate and 'froth' the oil).  The only
>>time the hi-vol capability will be needed is when the engine is
>>very old or has an internal 'leak'.
>
>WRONG.  Why the heck would it be called a high volume pump if it didn't pump
>more volume per revolution?!?!?  If you carefully compare the stock pump
>with a high volume pump, you will note the body of the pump is longer,
>denoting longer gears in the pump, and thus more swept area of the rotors.
>More area x same RPM = higher volume.  This will equate to higher average
>oil pressure, all else being equal.  The only circumstance the oil pump
>recirculates is if the filter is allowed to clog up, at which point there is
>a bypass valve in the block which still allows oil to circulate, albeit
>unfiltered.
>
>> - you are advised to buy a hardened, stronger oil pump drive shaft
>>when you get a hi-vol pump ...... this implies to me that there's
>>more of a load on the shaft, hence on the cam gears, on the cam
>>'bearings',on the timing chain and gears.  Why would you do that?
>
>The increased load is proportional to RPM.  If you plan on redlining the
>engine at 8000 RPM, I would recommend the hardened shaft, if you don't plan
>on running above 5500 or 6000 RPM, don't bother. 
>
>> - my 302 in my F150 with 107,918 (as of this morning) reads very >near the
>same oil pressure it did when it was new (on the "A" of >"NORMAL", heh-heh).
>It does this even when hot, down a quart and at >idle of 650 rpm (once
>again, as of this morn).
>
>All this means is that your engine is still in reasonable shape internally.
>A high volume pump doesn't last any longer than a stock pump under the same
>conditions.  
>
>>Neither my mentor/guru nor my part$ guru could tell me why I should
>>use a high volume pump.  Seems to me to really just be a waste of
>>_precious_ horsepower and a source of unnecessary wear on the cam
>>and related components.
>
>This is true.  Having cleared up a few inconsistencies in your above
>comments, there are very few reasons to use a high volume pump. To quote
>David Vizard (How to Build Horsepower, S-A Design Books):
>
>"Most stock oil pumps supply sufficient oil flow for modified street engines."
>
>"In most engines, abnormally high oil pressure (above 45-50 PSI), increases
>pump drag, absorbs engine power, increases the chance of oil entering the
>combustion chambers, and does not provide improved bearing lubrication or
>extend component life."
>
>"Higher oil pressure will almost always do only one thing: rob horsepower,
>often as much as 10-15 HP when pressures of 100 PSI are used."
>
>BTW, don't even think of re-using the old pump.
>regards
>dn
>dnorquay at iul-ccs.com
>
>
>

Tom Cloud <cloud at peaches.ph.utexas.edu>