[Healeys] oil pump
bspidell at comcast.net
Tue Oct 30 10:21:54 MDT 2018
re: "... delivery pressure itself is not that important and is really
just an indicator that oil is being delivered to the bearings ..."
Pressure is useful as a trend indicator.
On 10/30/2018 8:54 AM, Michael Salter wrote:
> I have a book "Repco Engine Service Manual" produced by Repco of
> Repco-Brabham fame that I use as my bible for engine building.
> On the subject of oil pressure it states that delivery pressure itself
> is not that important and is really just an indicator that oil is
> being delivered to the bearings.
> Of much greater importance is "thin film pressure" which is generated
> by the engine forces on a bearing which can be as high as 8000 p.s.i.
> at high RPM and is determined by the oil type and temperature, and the
> engine design.
> Based upon this I believe that concentrating on having good oil
> pressure at idle is wasted effort. What is important is that the
> engine has some pressure at idle but good pressure in the normal
> operating range.
> A pump which puts out a huge volume uses excessive horsepower and can
> result in accelerated wear of the pump drive.
> On Tue, Oct 30, 2018 at 11:30 AM Bob Spidell <bspidell at comcast.net
> <mailto:bspidell at comcast.net>> wrote:
> I'll offer what I know/have heard*. I have the 'high capacity'
> type in my BJ8, which is what the DWR techs/sales people
> recommended for a road car. Older 6-cyl cars had a rotor type
> pump. They (the rotor type) are supposed to be more
> efficient--i.e. they pump more oil--at lower RPMs. At some point
> it was discovered, probably from service bay repairs, that this
> type of pump put an excessive shear load on the bevel gears on the
> cam that drive the pump, causing them to wear out. Later cars
> started getting the gear type pump, which is less efficient at
> lower RPMs but puts less of a load on the cam, and is probably
> less expensive to manufacture as well (esp. if the gears are the
> sintered iron variety). I think the bevel gears on the cams were
> re-engineered, IIRC they got an additional tooth to spread the load.
> The Welch HC pump is the rotor type. I did a full engine rebuild
> and installed the DWR HC pump; I didn't notice any pressure change
> worth mentioning--I 'gained' 15 PSI at idle when I had my gauge
> overhauled--but the 'high capacity' I believe refers to volume
> rather than pressure (which, of course, is mostly dictated by
> engine speed). The 'standard type' pump is a gear type, hence it's
> more appropriate for high-RPM race engines as pump flow is
> proportional to RPM, and at 6K RPM or more you'll get plenty of
> oil with less load from the gear type.
> I'm not positive, but if you look at the photos closely, you can
> see the 'gallery plug' on the top of the case. I suppose it
> allows inspection of the innards of the pump without having to
> break the case. I believe it's threaded so not likely to pop
> out. If you're getting a new pump you'll likely need a new drive
> shaft and, surprisingly, DWR sells it cheaper than our (US)
> vendors sell it at (I think they might import the DWR shaft).
> * apply appropriate grains of salt
> On 10/30/2018 5:12 AM, simon.lachlan at alexarevel.plus.com
> <mailto:simon.lachlan at alexarevel.plus.com> wrote:
>> Has anyone got the Denis Welch oil pump ENG672M? See:-
>> Their text:- “Heat treated castings for longer life and
>> removable gallery plugs to be sure it is clean are advantages
>> of both types of oil pumps we offer. We recommend the high
>> capacity for all road engines using a standard type crank up
>> to 6000 rpm and the standard pump for race engines, steel
>> cranks or anything over 6000 rpm. Both are precision machined
>> and assembled in-house to control the highest quality.
>> - ENG672 is the standard type.
>> - ENG672M is the high capacity pump.”
>> What are “removable gallery plugs”?
>> Is it just me or is the above a bit counter-intuitive? “High
>> capacity” for road cars and “standard” for race engines? Surely
>> the highest capacity is needed where the engine is working
>> hardest ie racing?
>> And don’t I remember that, with the standard BMC pumps, the older
>> type is reckoned to be better than the newer type? Is this
>> something similar to Denis Welch’s two pumps?
>> Anyhow, if anyone’s got one…..what’s it like? Did the oil
>> pressure improve at all?
>> I’m guessing that most people will have fitted one as part of a
>> big rebuild thus they won’t have straightforward “before and
>> after” comparisons. I’m thinking of fitting mine to my engine as
>> part of a small winter project and hope I can squeeze a few more
>> psi into the system.
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