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K20 Camshaft Discrepancy

1387 Views 5 Replies 3 Participants Last post by  TheLastMentor, 
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All, my stock FD2 had relatively high camshaft wear hence I switched it with an identical pair from the same model and make as my car. My mech also verified that it bolts on perfectly but pointed out what I am also about to share.
Its been months since its install but the following has been bugging me. The surfaces I have circled out are very different, even my mech said it looks and feels different (when you run your hand on it) to the stock ones I had on the car. Can anyone clue me in on this?
I am unable to find an explanation.
Photos below for reference.
Mine:
Motor vehicle Automotive exhaust Rim Automotive tire Gas

Motor vehicle Gas Automotive exhaust Vehicle Auto part


The "new" cams:
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At first I disagreed with you. I thought they were just "heat-treated" lol. Then I looked closer... Those been used mate. You can see where the lobes have hit the valves in the middle.

Those marks are probably balancing tacks, from the crank being balanced.
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You are saying it was heat coming from the valvetrain that marked the cams @Them Witches ? I'm not sure what exact tool steel is used for cams, but 8620 starts melting at 750F, so something better than that. Gas has an auto-ignite temperature of about 560, EGT's can run anywhere from 1300 to 1600. I figured it was leftover markings from induction style heat treating, because surely any cam going in the engine would need to withstand at least 1800F, and that means they all must be heat treated. The valves would melt way before the cam shaft... wouldn't they?
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