April 4, 1960
Bulletin No. SB-775
SUBJECT: AC M42K SPARK PLUGS
You are aware by now that the new 1960 model engines of 40 and 75 H.P., as
well as the 35 and 50 H.P. engines for 1959, develop a very high power out-
put. Along with higher power one also gets a corresponding increase in
cylinder combustion temperatures.
AC has now developed a new, improved plug for these engines which is identified
by the type number "M42K". This spark plug is an addition to AC's regular
line and tests have verified that it performs very satisfactorily in all sizes
of engines from 3 through 75 H.P. Recent field tests of this plug in 40 and
75 H.P. engines confirm preliminary factory tests which, when made, indicated
very favorable performance.
This improved spark plug is to become available almost immediately. As soon
as it does, we suggest stocking it in order to furnish owners of Johnson
engines with the latest, and very satisfactory, plug development currently
available. It will of course be used on production engines.
We suggest placing your order with your AC spark plug supplier now. The
AC44M Spark Plug is still recommended for engines of 18 H.P. or less. It
is suggested you use up your current stock of this spark plug in these engines.
JOHNSON MOTORS
W. W. DeWees
Service Department
WWD:eb
NOTE: Post on your Miscellaneous index.
W. W. DeWees