There
is a field problem with two popular engines in the medium duty
field. They are the Ford truck 361 and 391 cubic inch displacement
engines.
The 361 and 391 are
the same engine, with a slight increase in stroke accounting
for the difference in displacement. There have been two problems
that have come to our attention. The first is an overheating
condition that shortens the life of the engine below normal
expectations, and the second is excessive oil consumption
past the valves.
OVERHEATING PROBLEM
In regard to the overheating problem,
extreme care should be taken to maintain 100% efficiency in
the cooling system at all times, as it is evident that this
is barely sufficient in many cases, even when in the best
possible condition. The radiator should be kept entirely clean
of insects, debris, and dirt which may affect the flow of
air through the radiator core, and be flushed regularly, and
protected with a rust inhibitor (Stop-Rust) at all times.
Where
the climate is extremely warm, a low temperature thermostat
should be installed. Retarded timing also contributes to overheating,
so engine timing must be periodically checked. Of course all
the usual cooling system parts - water pump, fan belts, and
hoses--should also be watched and kept in good repair. Due to
the heat problem these engines should not be rebored over .030.
VALVE GUIDE OIL PUMPING
The oil going down the guides is a
simpler matter. The installation of our P.S. valve seals will
completely eliminate the excess oil going down the guides.
We have found some engines consuming a startling amount of
oil past the guides. At the time of seal installation the
intake manifold gaskets should also be carefully checked,
as this is also a potential source of oil entering the combustion
chamber in the valve area.
