Hello,
I have some specific questions for all you ace engine builders out there. I
have been helping a friend of mine put his car back together, and we have come
upon something that has us confused.
Here it is. 1973 MGB engine, bored .020" Pistons were purchased from we
don't know where, but each one is stamped ".020" on the top. One of the
pistons--only one-- has an arrow on the top of the piston, not "stamped" like
the size numbers, it looks more like it was engraved. This engine came as a
short block assembly, from a source we can't track down. The piston with the
arrow on it was installed in the number two cylinder with the arrow pointing
to the rear of the engine. All this stuff happened before I got involved in
this project, but yesterday, when I showed up to help install the cylinder
head, I noticed the piston with the rear facing arrow, and suggested that
maybe we should hold off putting the head on. It seemed to me that the arrow
should be pointing to the front of the engine. It also seemed to me that all
of the pistons should have a similar arrow, or some other marking to indicate
which way it goes in, since one of them does.
Since my friend does not have a factory manual, I figured the best thing to do
would be remove all of the pistons and look things over. That's what we did,
and this is what we found. All of the con rods were installed with the
casting numbers facing the front of the engine. All of the pistons have wrist
pin bores that are slightly off-center. All of the pistons were installed on
the con rods the same way with respect to the offset. The offset appears to
be about 3/16", but our method of measurement was crude. If you were to stand
in front of the car and look at the installed engine, you would be facing the
casting numbers on the con rods, and the measurement from the centerline of
each piston's wristpin bore to the cylinder bore would be less by about 3/16"
on the left side. In other words, the way this engine was put together, the
distance from the center of the wrist pin to the cylinder wall is greater on
the intake/exhaust side of the block. Is this correct? Does it matter? If
it is wrong, can we simply turn the whole piston/conrod assembly around so
that the casting numbers on the con rods face the rear of the engine, or do
the con rods need to be installed with the casting numbers facing forward?
TIA!
Rich Rock
ps. One more thing...What is the torque spec for the con rods
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