hardend valve seats
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Junior User
Joined: Dec 2000
Posts: 70
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hardend valve seats
I am fixing to have my heads reworked and the machine shop told me that I need to only have the exaust valve seat hardend not the intake.But my dad says I should have them both done.What do yall think.
Senior User
Joined: Jul 1999
Posts: 472
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From: USA
hardend valve seats
Hardened exhaust valve seats are required on the exhaust side only (due to operating temp) and needed for operation on unleaded fuel - especially if the engine has valve rotators on the exhaust valves. The hardened seat rings are made of a better material (alloyed with nickel and chromium) than cast iron.
Should intake valve seats need to be installed, the standard practice is to install plain cast iron seats, as hardened seats are not required. Remember intake valves run much cooler than exhaust valves!
I installed hardened seats in the heads of one of the 400's I rebuilt, as the exhaust valves receded into the heads on that engine - as much as .140". That particular engine was never apart before either. The symptom was a "dead cylinder" having good compression, good spark, and of course, gasoline.
Art
Should intake valve seats need to be installed, the standard practice is to install plain cast iron seats, as hardened seats are not required. Remember intake valves run much cooler than exhaust valves!
I installed hardened seats in the heads of one of the 400's I rebuilt, as the exhaust valves receded into the heads on that engine - as much as .140". That particular engine was never apart before either. The symptom was a "dead cylinder" having good compression, good spark, and of course, gasoline.
Art
Senior User
Joined: Oct 2001
Posts: 113
Likes: 0
hardend valve seats
I've never installed a hard seat in anything. I always run stainless valves though and bronze guides. My heads last as long as the rest of the motor does. Other than normal wear I haven't had any problems so far. I think my cast iron race heads have plasma / flame hardened exhaust seats(whatever that is).
