Why is one 340 connecting rod bronze color?

Hmmm. So if the rods are copper plated to prevent the rod body from being hardened, at what point would that copper be removed? When they were tossed into the NO-GO bin, were they still copper platted? At what point do the rods get shot peened?


?? no production rods at Trenton engine during the time I worked there were ever shot-peened. They came (raw blanks) in a bulk bin that hit 8 different workstations to process through the system.
1. blanchard mill to grind the sides to spec on the rods. (it's fun when a 400lb grinding wheel starts to chunk off and vibrate, can you say run for your life and keep going at least 100 yards or you WILL get hit.)
this is a tiny one that is similar to the cap blanchard. 18" tall and 42" in diameter. the rod blanchard was 24" tall and 48" diameter.
blanchard_18d___42.jpg

2. then on a overhead conveyor to go to the 4 natco's that drilled the wristpin end.
3. broached on the big end size and cap mating surface. (no caps on yet)
4. rods bolt holes and bearing locator drilled and ground right after the broach for rod bolts and mating surface
5.Caps went similar to the rods Blanchard mill for the sides, natco or bhures to drill the cap end and the bearing locator groove then through a smaller broach to do the bearing surface.
6. Cap and rod are now matched using a bolt press and torqued to spec. hung on the conveyor going through a washer to go to the next station.
7. major honing station for both the wristpin adn crank end. rehung and rewashed to final hone.
8. final honing and gauging (good goes on and bad hit 1 of 2 bins (under.020 or scrap)

copper rods come in from the platers in bins and only go through the final hone and gauging then on to the engine assembly line.