> I haven't heard that (sounds good though)), but I have heard that by
> having your sump overfilled that you don't properly lubricate the
> cylinders. That is, the throws on the crank actually splash oil up
> into the cylinders. Can anyone verify this? It sounds good to me,
> but I've heard of race engines that have made their cranks have thin
> throws on their cranks so that the crank slices through the oil.
Ooooh, yeah, that's a way cool thing to do to a race motor. The idea
is that since these things are spinning at 8000 or 9000 RPM (and there's
a lot more you have to do in order to keep them in one piece at those
speeds), you knife-edge the crank for minimum drag, both in the oil and
in the vapors.
> If
> that's the case, my theory about spashing oil into the cylinders is
> shot. So how do the cylinders get lubrication?
On the MGB, there's a little spray nozzle at the top of the connecting
rods (at least on the angled big-end rods) that shoots a squirt of oil
up into the inside of the cylinders. This also helps to cool the bottom
of the pistons to some extent. It's what the oil control ring is
meant to, well, control.
For super-high RPM operation with a B, you need not only to balance
and lighten the crank, you also need to take great care to polish
the intersection of the crank journals with the crank throws. That
interface requires a radiused corner, not a sharp edge, to avoid a
stress fracture at that point. Furthermore, you need to cross-drill
the crank and chamfer the exit holes for the lubrication. On MGBs,
the oil goes into the crank at one point (rats, can't remember where)
and squirts out at 50-90 PSI in every bearing. On a stock motor,
there is one exit in each journal; on a full-race motor, you drill
a hole all the way through the journal so that the oil flows out
both sides of the journal (and you use a stiffer oil pressure relief
spring to keep the pressure up). You also grind the exits of the
oil passages so that the oil flows most smoothly out of the crank
and into the bearing interface. Butch Gilbert claims to have seen
8800 with reliability on his motors done this way; I don't know
how much of that is bench racing and how much is accurate reporting.
Butch has been right-on in a number of other areas, though, so I'd
tend to believe him on this one.
--Scott
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