I have a ’54 331 in my ’27 T roadster. Right now it is pretty much stock, but over the winter I hope to rebuild it. I have found a few places that will do the machining and one of them tells me that the engine was originally built with hardened valve seats. Anyone here know anything about this ??

i have been told the same thing by a guy that was sold a job by machinist---machinist claimed he put in the hardened seats and it was later discovered he only cut the existing ones.....sounds like you found a good machinist.....

All the first gen HEMIs I've had apart have had factory installed hardened exhaust seats.

OK... Thanks for the information. How do you tell if the seats are hardened ??

The hardened seat is a separate piece that is pressed into the head (Upper seat in picture) instead of being ground directly into the head like the lower (intake) seat. It’s pretty easy to tell once you get the valves out.





Speaking of valves most (all?) of the first gen HEMIs used sodium filled exhaust valves. Basically the valve was made in 2 pieces (head and stem) and welded together. Any pitting in the weld area just under the valve head pretty much renders the valve unsafe to use.

The factory parts catalog shows the exhaust seat (9-39-9) used up through the '58 392.

...sadly, there is some mis-information posted here.

The ONLY sodium filled valve is from the truck engines and easy to spot since they had stem od in the 0.4375" range.
Although the hardened insert was used and shows in the parts catalogue MaMopar also used INDUCTION hardened seats on many engines. These will be evident after cleaning since there will be heat discoloration.

Thanks guys, for all of the info

Kip