Hardened Valve Seats

[cuthbertdavies]

I have read that when rebuilding the head on a JD 420 you should install hardened valve seats due to the unleaded gas we use today. I also understand that the 420 did not have replaceable valve seats. Would you have a machine shop machine the head to accept the hardened seats and install them? Would you do the intake valves also or just exhaust?

[Lavoy]

Yes, machine shop would need to do it, it isn't expensive, cheap insurance. Ask them as to doing both intake and exhaust.
Lavoy