Balancing my pistons was
pretty straight forward. All I had to do was install the
rings and place the pistons on my digital scale. But
balancing the rod ends proved to be quite difficult. I could
not manage to get the rod placed back on the scale in exactly the
same spot every time. Sometimes I had as much as a 50g
difference between one placing to another. Every jig I made
was either not accurate enough, added friction resulting in
uneven support, or added loads to the rods which resulted in
I posted a message to the
CorvAIRCRAFT e-mail list, and I shortly had my answer.
Don McGehee sent me a private e-mail with
this attached drawing of a jig which was drawn from memory of one
he saw in a hot rod engine shop.
From his drawing, I made this jig.
I turned 2 phenolic disks which slide freely
over a shaft, which lowers friction and allows
me to change the disks from one shaft to the other, for
balancing each rod end.
Although the centers of the shafts are
the correct distance apart, the chain all but eliminates any
unwanted side loads.
I've been able to remove and replace the
connecting rod on this jig, and if it's not exactly the same
weight when I make the change, it's only 1g difference.
One good thing I've found out from this exercise is
that the stock connecting rods are very close anyhow. From my
heaviest to my lightest, there's only a 7g difference.