>> Now, on to display my ignorance: I have never quite understood the
>> mechanics of why bearing clearances affect oil pressure - anyone
>> care to offer up a quick tutorial?
>>
> Think of the nozzle on the end of a garden hose. As the opening is made
> larger, the water emerges with less pressure. As it gets smaller, the water
> emerges under greater pressure, so you can spray the effing salt and snow off
Now envision a 1/8" pipe heading 12" upward from the nozzle. This is
your rocker feed. With the nozzle open, the water gushes out under little
pressure and the oil going upward is nill.
Replacing the bearings, closes the gap, raises the pressure and causes the
oil to flow into the rocker shaft at 50 psi again, forcing it out all those
little holes.
While I'm on the subject of dry rockers, the shaft can rotate and cut off
the 1/8" feed if the screw in the back isn't in place. This shaft is
hollow with a lead plug in each end. Guess what happens when it sits
for years... the oil solidifies and the shaft gets clogged, ditto for
the small rocker feed holes. This means you have some wet and some dry
rockers. Removing the caps or soaking in carb cleaner may fix this.
The external feed works by tripling the volume of oil going to the rocker
by pulling it right off the pump instead of the galley. I suspect this
lessens the main bearing volume somewhat.
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Roger G. Bolick, rgb@exact.com, (512) 794-9567, FAX 345-2879
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