----- Original Message -----
From: "David Kernberger" <dkern@napanet.net>
To: <buick-rover-v8@autox.team.net>
Sent: Monday, September 04, 2000 1:13 AM
Subject: Muddying the waters?????
>
> Other things being equal, the following relations are generally true:
>
> 1) Increasing pump capacity will increase pressure at all engine
> speeds up to the pressure relief valve setting.
>
Neil writes:
One small correction. The back pressure is not constant as engine speed
rises. It is this back pressure that is registering on your gauge and is a
result of trying to stuff the oil through the various oil passages.
The volume of oil delivered by the pump rises directly with the speed of the
engine. But as that volume of oil flowing through the passages increases,
the back pressure rises at a higher rate (with the square of the speed, I
think, such that a doubling of the speed results in a four fold increase in
the pressure). As stated elsewhere this continues until the relief valve
lifts, whereupon little further rise will happen.
> 2) A stiffer bypass valve spring will only raise maximum pressure
> and, even then, only if pump has sufficient capacity.
>
> 3) It is very difficult to define any particular system as
> inherently high volume or high pressure.
I think that what those who are careful with their words really say about
the BOP/Rover V8 is that it is an engine that relies more on volume than on
pressure to provide proper lubrication. There's always a tradeoff between
the two.
The specs GM gave Road & Track when the engine was introduced say that the
pressure relief valve was set at 33 psi. What oil did GM specify for the
engine when it was in production? Sounds like stock engines in Rover
applications were a couple of pounds higher. The MGB V8 was higher still,
but Hardcastle's opinion was that this was based not upon the needs of the
engine but to reassure MG buyers who were used to seeing higher oil
pressures.
>
> 4) Increasing oil viscosity will increase pressure at all speeds up
> to the pressure relief valve setting.
And so, it should be specified when quoting oil pressure specs.
>
> 5) A new engine will show higher pressures than a worn engine.
>
> The other factors of relative load on the drive gears, effects of
> closer manufacturing tolerances, old versus new oil recommendations, ete.
> etc. etc. have been well covered by others with more experience than I.
>
> Thanks for listening, if you did.
>
> Cheers,
>
> Dave K.
>
>
> ----------------------------------------------------------
>
> >Frankly Glen, I limit my comments to this and other lists because of
responses
> >like yours. I'm not speaking of list surveys nor am I guessing. I'm
speaking
> >from 20 years hands on experience with TR8s, street cars and a race car,
and
> >having built a number of engines. I currently have a fully built 4.6 and
> >a 4.2
> >short block on engine stands. The TR8 factory manual specifies 1.97
> >kgf/cm2(28
> >lbf/in2) pressure at 2000 rpm and 35 lbf/in2 at 2400. Given your
assertion,
> >that would mean that pressure at idle, 750 to 900 rpm, would drop as revs
> >rise,
> >a most unusual circumstance. One would also then have to wonder why
there
> >is a
> >pressure relief valve in the system. You apparantly do not understand
the
> >proper and careful building of an engine, often refered to as
"blueprinting".
> >It means in essence to optimize clearances and mechanical relationships
to
> >approach that intended by the designer, removing manufacturing variances.
A
> >blueprinted bottom end would give results reflecting just what the
designer
> >intended, in oil pressure and in other ways. That is the way that race
> >engines
> >such as those I have built, using stock components, are put together.
You
> >apparantly do not understand oil viscosities either. 20w50 is one of the
> >viscosities recommended for the TR8, but not the only one. It was a
> >common oil
> >in the 70s before the feds imposed fuel economy standards and before
> >manufacturing processes allowed much less variance in clearances as is
now
> >true. Engines running the same bearing clearances now use 5w30 because
it is
> >easier to move at cold start, resulting in less wear in that time when
> >most wear
> >occurs, and because it contributes to fuel economy. Increased pressure
in
> >itself does not incxrease protection or lessen friction. It is necessart
only
> >that there be sufficient pressure to maintain the oil film that separates
one
> >part from another. Smokey Yunick, one of the most respectred
"hotrodders"
> >ever
> >has often stated that an engine needs only 10 #/in2 per 1000 rpm. 20w50
> >and the
> >like is often used in engines with larger clearances due to wear. You
are of
> >course entitled to use that which you choose, but it is not helpful to
make
> >guesses without the background needed to understand what is actually
> >happening.
> >Am I a hot rodder? Perhaps, but I respect the advances made by those
much
> >more
> >capable than I. Do you still use the tires, lubes, fuel and coolants
> >originally
> >specified. I doubt it, because most are no longer available, having been
> >supplanted by newer products. John
> >
> >Glen Wilson wrote:
>
>
>
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