It's not the valves that need to be hard, it is the exhaust valve seats. In
many older engines, the head cast iron was used as the valve seats. You can
have the seats milled out and hardened inserts put in place to prevent valve
seat recession due to the lack of lead in gas.
The good news is that the R6602 has hardened valve seats in the exhaust valve
position already. The exhaust valve also has a rotator on it. Also, the
exhaust valves are filled with sodium to help cool the exhaust valve. Nothing
but top notch stuff here. This was really high tech stuff back in the 50's when
this engine was designed. Consequently there is really nothing needed to run
this engine on no-lead gas. I've been using lead additive anyway, but it is
getting really hard to find. After looking this up, I'm going to stop that
practice. The valve that is susceptible to valve seat recession is the exhaust
valve. They get so hot that they actually weld themselves to the seat just a
little bit and gradually tear off small parts of the seat until the valve moves
into the head. Hence valve seat recession. The lead in the gas used to keep
this welding process from occurring. The hardened valve seat should prevent
that and the sodium filled valve should help conduct the heat out of the valve
and into the stem where it can be cooled by contact with the valve guide.
I'm constantly amazed by the high tech stuff used in these older MVs. I guess
that is why they cost a small fortune when originally made!
BTW, I got this info out of the RM9-2805-203-35 Field and Depot maintenance
manual for Engine, Assembly W,Accessories (Continental Model R-6602) Jan. 1965
M51 w/R6602
Dave
nick chance wrote:
> Can anyone out there confirm if the R6602 engine (as fitted to the early
> 5-ton M series trucks) has harden valves. Mine was fitted in 1969 & has done
> around 2500 miles since. Now it has just blown the head gasket & as I have
> to take the head off anyway I might as well make sure it can take Unleaded
> gas.
>
> Thanks
>
> Nick
>
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This archive was generated by hypermail 2b29 : Sun Sep 02 2001 - 11:15:39 PDT