[Healeys] oil pump
bspidell at comcast.net
Tue Oct 30 18:54:59 MDT 2018
Probably due to aeration (foaming) of the oil due to cavitation. When I
was bringing my BJ8 home from my dad's after after installing a rebuilt
engine, I cracked the pan on the concrete lip of his shop (but didn't
realize I was leaking). As I drove home, I saw the pressure at speed
drop from 55psi to about 35psi and thought: "Hmmmm ... that's odd."
Stopped on the driveway for just a couple minutes while I opened the
garage door and when I pulled the car into the garage there was a small
puddle on the driveway (mystery solved). Welded the pan and added a
couple quarts and drove it a couple hundred miles--at normal
pressure--before replacing the pan.
The oil pressure gauge indicates both long-term trends (e.g. bearing
wear) and short-term (oil loss). If you had an oil temperature gauge
you'd see the temp go up if you're losing oil, as the oil becomes less
On 10/30/2018 4:24 PM, Michael MacLean wrote:
> Well then please explain to me how a Bugeye I owned in 1971 would drop
> from 60 PSI at speed to 40 PSI over a period of time. When I checked
> the oil it was a quart low. Adding a quart, the "at speed" pressure
> returned to 60 PSI. I mean it was great to have a low oil indicator
> like that, but I never understood how it worked.
> Mike MacLean
> On Tuesday, October 30, 2018 2:22 PM, Michael Salter
> <michael.salter at gmail.com> wrote:
> Yes, absolutely true Bob.
> Decreasing oil pressure can certainly be an indicator of increasing
> On Tue, Oct 30, 2018 at 12:22 PM Bob Spidell <bspidell at comcast.net
> <mailto:bspidell at comcast.net>> wrote:
> 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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