RE: No lead

["Dodd, Kelvin" <doddk@mossmotors.com>]

> When did the MG's start using hadened seats? I think the 
> american built cars
> started using unleaded gasoline in about 74 or 75.

Eeek.  I knew I should have kept quiet.

        Off the top, I can't find any engine number specs.  According to
Lindsay Porter "BMC and Leyland B-Series Engine Data" only the Fed engines
got the hardened seats. The hardening process was very involved and
expensive.  There were many other changes made to the engines so that they
could meet federal standards with some hope of longevity.

        I would imagine that only the cat equipped, or perhaps cat prepared
engines were modified.  There was a comment that the valves were down sized
at the same time and the rocker oil gallery offset.  I don't know if the
change back to the earlier small intake valves coincided with the offset oil
hole.  Bets are the big valve 73-74 heads were the last US spec heads with
non-hardened seats.  That would explain why both the heads I have with
eroded seats are big valve.

Kelvin.