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Original Message
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| High Volume ~v~ High Pressure pumps |
| By P - 10/08/2003 4:37:28 PM; IP 66.89.75.42 |
Although this is discussed in a following thread, I wanted to post it under the title noted so people could see it better, rather than hide it within some other thread.
The following was from a conversation "we" had on another forum, regarding marine FE motors. It is, however, very informative and from two guys who know what they are talking about. In the event Royce, Dave Shoe, Mr. F, etc., disagree with what is said here, please advise, otherwise I'm considering it the gospel.
regards to all, P
"I have to chime in on the oil pump subject, as I've built several
engines with a variety of oil pumps, both normal rebuilds and high
performance engines. As "P" and others have stated, the standard
oil pump is just fine and will work OK in marine applications, but, I
want to clarify an advantage to using the HV (high volume) pumps that
I have enjoyed and that many may not be aware of. First, a couple
statements on the these different varieties of pumps. The standard
pump is just that, desgined to pump the same volume of oil and
maintain the same lubrication system pressure as the OEM pump the
engine was built with. Pumping chamber/rotor volumes are the same as
the OEM pumps, and the pressure relief spring is set to the same
relief pressure as the OEM specs. High volume pumps utilize
(typically) a taller rotor and pumping chamber volume, and as such
they can pump 10-25% more oil than a standard pump per revolution.
And, the HV pump pressure relief is set at (or close to) the OEM
pressure relief spec. What does this mean? At higher RPMS on an
engine with standard bearing clearances (let's say 2500RPM or so and
above) your standard (or high volume) pump, without pressure relief,
would raise the lubrication system pressure to very high (80-100
psi+) pressures, and bad things will happen (ruptured oil filter,
etc.), but, of course the pressure relief bypass opens and regulates
this to a safe pressure (50-70 psi), so these bad things do not
happen. Note: Once you get to the relief pressure (and assuming it is
the same for both pumps), both HV and standard pumps will flow
exactly the same volume of oil through the same engine! So you might
ask, why do I want an HV pump? Simple, at low RPM (i.e. below the RPM
that the relief spring opens) the HV pump will put out a higher
volume of oil, and thus carry a higher oil pressure than a standard
pump at the same RPM. An example would be: let's say your engine
holds 24 psi at hot idle, and 60 psi at cruise rpm with a standard
oil pump. Changing to a HV pump on the same engine will raise the
hot idle oil pressure (to like 30psi), and the pressure (and volume)
at cruise rpms will remain unchanged (assuming similar relief valve
settings in the HV pump). I like a bit more oil pressure at low RPM,
and as such , lean toward the HV pumps, even in stock rebuilds.
Another potential advantage with the HV pump is if something goes
wrong and comes apart causing an internal "leak" in the lubrication
system, (like you throw a pushrod and a lifer comes up out of it's
bore), the HV pump may be able to move enough oil to keep up some
level oil lubrication pressure in the engine to let you limp home,
whereas a standard pump may not be able to keep up with the
internal "bleeding".
To round out the categories: The HP (high pressure) pump is just a
stock pump with the pressure relief spring shimmed up or replaced
with a stiffer spring to raise the relief setting. Running higher
pressures will move more oil through the system and can lead to oil
starvation ("empty pan - all oil in the valve covers/lifter valley"),
so be careful. The HV/HP pump is an HV pump with the same relief
setting modification, and can move even more oil before the relief
opens, so it is particularly suited to causing starvation problems
with a stock pan, pickup, and drainback, so avoid it on a "stock"
rebuild. It is intended for engines with more bearing clearance
(less drag for more HP)and more perfomance oriented oiling system
preparations.
So, the standard pump is fine, but make mine HV, and avoid the HP and
HV/HP variants on your marine FE engine! "
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Hope this helps you automotive FE owners make an informed decision regarding which one is best for your application,
P
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This thread, so far...
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