Icon IC 743 piston weight incorrect

pishta said
The guy at an import race shop takes the marked rods apart, balances all the tops to the lowest weight off the tip pad, and then balances all the bottoms to the lowest weight off the bottom pad. Said he did this forever and it always worked. It sure is easier than rigging up our jigs and trying to get repeatable weights using a fixed or swinging pivot, consumer grade scales, etc.
Notice the last line of the post #19 that states the magnum rod is thinner at the little end so if you buy Magnum pistons for LA rods youll have to closely check side clearance of rods to block. I took weight out of the end of the pin (actually making them 2mm shorter as it was the free end of the pin and it was a press fit pin on the rod so it didnt move once it was installed on the journal. My MP pistons and pins were up to 12g variance from each other!

Hey Pishta... interesting info on the import rod work. However, for 4 cylinder inlines (or any inline), the reciprocating and rotating weight parts are not separated out; the whole piston-rod assemblies are weight matched against each other. So unless he is working on imports like V6 Z engines, etc. his technique does nothing of benefit (that I am aware of).

Yes, that is plenty of piston/pin variance! The performance brands usually come very closely matched.

And interesting on the pin mods.... as long as you keep the weight bearing length of the pin in the pin bore adequate and keep the pin centered (and not floating too much back an forth) then that can work. The older pistons seemed to keep around 0.7" of weight bearing length between pin and pin bore, but I've seen just under 0.5" in modern engines. It would be interesting to survey a whole lot of pistons at different power levels to see what is used.