1974 351w
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Joined: May 2004
Posts: 12,170
Likes: 5
From: The hills of No. Calif.
Depends on how they rebuild them. First of all, you don't really have a choice since leaded gas isn't available any longer, except for very expensive racing gas and some aviation fuel.
If the seats are badly worn they may have to cut into them fairly deep to clean them back up. These heads didn't come with a hardened seat insert, they simply cut the seats into the cast iron of the head and then hardened the area around the seats themselves. For a simple valve job it's not a problem, but if you go with oversize valves they cut in past the hardened area. If they have to cut in deeply to restore the seats, then they should install hardened inserts to bring the seats back down to stock size.
If the seats are badly worn they may have to cut into them fairly deep to clean them back up. These heads didn't come with a hardened seat insert, they simply cut the seats into the cast iron of the head and then hardened the area around the seats themselves. For a simple valve job it's not a problem, but if you go with oversize valves they cut in past the hardened area. If they have to cut in deeply to restore the seats, then they should install hardened inserts to bring the seats back down to stock size.
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