The cast crank will have a narrow (around 1/8") flash seam on the counter weights where the sand molds fit together. A forged crank will have a larger seam (around 1/2 to 3/4" wide)
-- Edited by hemi43 on Sunday 8th of September 2013 09:47:42 PM
I picked up a 350 block 4 bolt mains and it id's as an 80 from larger than a 3/4 ton truck. ID # K03 12 TMZ supposedly a forged crank but how do you tell for sure? I'm sure someone on here knows how to tell the difference and will share the info with me. thanks Larry
A badly cracked forged crank will thunk like a cast crank. Easy way to check before sending a forged crank for magnafluxing - pic it up with one hand so its hanging (I just grab a counter weight) and give it a light hit on another counterweight with a hammer. It will ring like a bell if it is not cracked or has minor cracks. If it thunks like a cast crank, its not any good.
Factory 1053 steel forged cranks have a much higher tendancy to crack than cast iron, so I would magnaflux it before running it. If the journals are torn up, just grind it and don't worry about it if it ends up 20/20 or 30/30. You can even get get 40/40 bearings for it and if you have it ground with a large radii on the crank cheeks, it will be stronger than a std/std crank with factory radii.
