Another engine that's in for a rebuild at my shop...
Someone had rebuilt or tuned it up before, and whoever it was, had conveniently marked each connecting rod with a punch. 1-2-3-4. Very nice, thank you.
But if he bothered to do that, why didn't he bother to weigh them puppies?
1: 569g 2: 576g 3: 593g 4: 580gA whopping 24g difference! These rods never left the factory in the same engine, someone scraped them together from a parts pile and threw them in this engine without looking twice. Factory rejection limit for weight difference is 8-10g. Rods were made in 2 or 3 main weight groups. Rods from different weight groups were never used in one engine.
Because of this... I can't continue assembling the customer engine until we find a matching set of rods.. trying to trim 24g off a stock rod is impossible, without major sacrifices to reliability. I hit my own diminishing parts stash and found him a 580g rod, resulting in a weight distribution over 11g span. Much better, and trimmable... but still requires a lot of grinding.
Maybe this message works as a reminder for someone who is building one of his (or her!) first engines.
Jan