Why you shouldnt put seats in the heads on any of the nailheads. This is a late head. The early engines have even less material.. Then factor in core shift and 60 plus years of corrosion. But bottom line is these engines dont need them. We havnt had lead in the gas in 40 years and theres no signs of valve recession due to high nickel content. If your heads have recessed seats from excessive grinds/ poor machine work, or heavy pitting from water damage, start with a good set instead of dumping money into a mistake. Even if the heads dont crack upon seat installation, chances of the head still cracking later on after being put into service is still probably 75% likely. Might be a week, might be 5 years later.. If a machinist tries to sell you on hard seats, they are either trying to get more money out of you, or they dont know what they are doing. Take your engine elsewhere. Weve also found that you should stay away from bronze guides... And thats due to harsh rocker geometry and very loose required guide clearance. (.002-.0025 on intake .003 to .0035 on exhaust) And bronze guides dont hold oil like iron. You can get away with running bronze guides with roller rockers though. With TA rollers you need seals on both intake and exhaust, because they allow too much oil to the top end. Otherwise, never run seals on the exhaust or they will run too dry and gall. We buy cylinder heads by the pallet from our suppliers and cant keep them in stock ...
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