Star Re. Box 357A Detroit Lakes, Minnesota 56501
The purpose of this article is to discuss problems which often
occur in the valve train of the Associated and Galloway engines
that use a flat valve pushrod supported by two cast guidesone on
the block and one on the cylinder head. I have encountered problems
on the two engines and I imagine the same situation could exist on
other engines of similar design.
What happens is that the pushrod wears on the bottom side where
it passes through the guides. The guides also wear some. When this
happens it allows the centerline of the pushrod roller to drop
below the centerline of the cam gear. When the cam lobe contacts
the pushrod roller, it tries to push the roller down rather than
forward. This causes everything to bind and puts a strain on all of
the parts involved. The result is excessive wear on the gear teeth.
In one case, it broke teeth out of the cam gear and on another
engine it broke the casting that holds the cam gear pin.
To check for this problem it is necessary to remove the
crankshaft and flywheels from the block. Check for timing marks or
mark the gear so the timing will be right when you put it back
together. Make sure all the contact surfaces along the valve train
are lubricated. Then turn the cam gear by hand in the normal
direction of rotation this is opposite of flywheel rotation. The
gear should turn freely through a complete rotation without
binding. If it doesn’t, check the pushrod and guides for
wear.
The agricultural machinists of yesteryear had a simple and
effective remedy for this situation: cut some strips of galvanized
tin and slip these between the pushrod and guide. Leave the strips
long enough so you can wrap the ends around the guide to hold them
in place. This repair solves the problem, but it doesn’t look
real cricket on a restored show engine.
The best way I’ve found to repair the pushrod is to build up
the worn places by welding and then grind and file the welding to
the proper dimensions. In this way if the guides are worn, you can
build the rod up oversize and fit it to the worn guides. If the
guides are worn real badly, they can be built up with nickel rod
and filed to shape. It is also a good idea to check the pushrod
roller to see that it turns freely and doesn’t have any flat
spots. If you have your own machine tools, it is not difficult to
make a new roller or any machine shop can make one at a minimal
cost.
By checking for this problem and repairing it if necessary, you
will probably extend the life of the gears and avoid some serious
damage. I hope this information will help someone so they don’t
have to find out the hard way!
