Let's not get too far off track here!
First off, regarding a cam lobe failure on #3 being related to a a piston
holeing
on the number 3. It wouldn't be as a result of oiling issues because all the
cam is oiled from the rear of the head, behind the #4.
If you floated a valve on the number 3, that could wipe out the cam and the
piston.
But that could happen on any cylinder, not just number 3. That doesn't look
like
what happened to Victors.
The U20 piston also is know to fatigue around the pin boss and under hard,
sustained use will lose the skirt. messy.
Regarding Victor's piston, From the photo it looks like it really melted, so a
detonation,lean or excessive timing issue. At 5200 rpm's detonation can be
impossible to hear, good chance that was it!
Don't lump the number 2 or 3 rod bearing failures from the r-16 (GP) into the
U20.
The U20 doesn't have any inherent cylinder faults like the 1600.
Those of us who have built a lot of modified R16 engines, know about the 2/3
problem. It is inherent in the oiling system of both the 3 main, and
5 main R16 designs. With quite a bit of money and specific machine work it can
be eliminated. Nissan eliminated it for us in the U20 design.
Jim
What Mark wrote below only applies to R16's:
Mark van der Hoek wrote:
>
> Paul wrote:
> >
> > It would appear that it might have something to do with the oil feed
> also?
> > I have been working with SCCA GP racer Jim Sloan this spring. He was
> > commenting that #3 crank journal is always the one that burns when he loses
> > a motor on the track. He quickly explained the stock oil flow through the
> > crank, then talked about the modifications he currently makes ( enlarged
> oil
> > passage in crank and journal bearing ) and went on to talk about the
> > possibilities of cross drilling the crank for still better oil feed.
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