Like Jim Pepper says “little changes to an engine all add up”. I’ve done a couple of sixes and in each case I balanced the rods and pistons. Nothing scientific and certainly not ‘blueprint balance’. Flathead sixes run smoothly anyway, but I can’t help thinking that the little balancing I did did help. Especially when I recall dropping one of them out of overdrive and keeping it there until it hit 80 mph – and it seemed as if I could have gone further.
So here I am with my postal scale and a batch of rods. The weight showing on the scale isn’t as important as all rods having the same number. It would be too much for me to try to balance each end of the rod separately so I’ll just go with a total weight. Of the eight rods #5 & #8 were the low ones at 632g. The high was #2 at 638g with the others somewhere in between.
For the most part I tried to grind an equal amount from the top and bottom ‘lumps’ The heaviest one I smoothed out the casting ridges on the arm – you can just see it in the background. I was very careful here to just remove the excess metal and I didn’t leave any sharp edges. I ground a gram off each side.
After all that grinding I wanted to be sure that all the filings were removed. I thoroughly scrubbed each part in the parts washer and then blew out all the openings – especially the oil hole in the upper shoulders.
Final step, I assembled each one with new .001 bearings, then coated them in Fluid Film and put them away until it is time to install the pistons.
Next the piston balance – an even more boring job as I have to use an small electric grinder to remove metal slowly.