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Old April 27th 08, 01:20 AM posted to rec.aviation.homebuilt
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Default Question for VW Engine Flyers

Standard for all engines having pressure-lubricated bearings is about
10psi per 1000 rpm at the engine's normal operating temperature. *

As a point of interest, under maximum load a VW converted to 1834cc
would produce about 78hp @ 4000rpm (ie, about 102 lb/ft of torque),
assuming you used big-valve heads and a Schneider 248F cam. At that
level of output, under Standard Day conditions, with a cooling air
differential equal to six inches of water, you could count on between
twenty and thirty SECONDS of run-time before your CHT exceeded the
recommended maximum of 450F. Which would be fine on the drag strip.

(Hint: Before spending any money on your 78hp engine (with reduction),
you might want to ask the seller if he's talking about PEAK or
SUSTAINED output. Peak is fine for hot-rods & dune-buggies but for
airplanes you need to know the engine's maximum SUSTAINABLE output
relative to its TBO.)

-R.S.Hoover

* -- Some engines having oil pumps do NOT deliver oil under pressure
to all of their bearing journals. The VW does so the 10lb/1kRPM is
valid. However, the stock VW oil pressure control spring is designed
to pop-off at 27psi. Increasing the oil pressure is SOP for any high-
output VW engine.