Mark,
Contrary to what the GT owner told you, the engine has (or at least we
can safely say it left the factory with) an oil pump. Because it has an
oil pump, it also has a spring and a relief valve, as these are there to
relieve excess pressure that the pump pumps over the requirements of the
engine.
The usual cause of oil pressure dropping off is that the oil gets
thinner as it gets warm. Worn bearings have greater space for pressurised
oil to flow through, hence the thin, warm oil runs through them faster
than it did when cold, and the pressure drops as the rate of flow
increases.
Find out from him--better yet, go driving on a test drive yourself,
then write back to the list what the pressure was when you started the
engine, and what pressure it was after 25 minutes of driving, and what
oil he says he is using.
John Twist advocates changing big-end bearings at 60,000 miles or so to
bring oil pressure back up to specifications. It's easy to do and is
effective as long as the main bearings haven't been chewed up from lack
of lubrication.
Take it for a drive and let the list know what you learned.
Bob
'72 GT
> "I don't know about driving it a great distance. After about 25
> minutes the
> oil pressure drops off. Now these MGs, they don't have oil pumps,
> they have
> springs and relief valves and stuff..."
>
> ...yes. Well. Anyhow, what would cause the pressure to drop off,
> except for
> a leak? It must not be leaking, because the pressure is evidently
> back when
> he restarts.
>
> TIA, and wish me luck,
> -Mark
>
> __________________________________________________
> Mark Dawson
> General Manager
> The Roundtown Cafi http://www.roundtowncafe.com
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