Camshaft Bush Modification -
prevention of leaks and noises from your engine
The
camshaft bronze bush is prevented from moving due to a small square head bolt,
which is located in front of the engine block. However, when this was new it was
not a problem, but after time the hole in the bronze bush and the pin start to
wear due to the continual lateral movement of the camshaft timing gear. The bolt
starts to leak..... and there is a slight increase in noise from the timing
gears.
So how
to over come this?
A good
suggestion from Tony Leslie [Holmsdale Sevens] is to replace this bolt and pin
arrangement with a stud and lock nut. This is similar to what Austin did on the
magneto engine [so why did they change?].
You
will need:-
1 x
5/16" BSF tap and suitable tapping drill; 1 x 5/16" dia drill; 1 x 5/16" BSF
engine block stud; washer and nut and preferable nylock nut [as it will seal
the thread from any possible leakage]. Fibre washer.
Carefully drill and tap the camshaft bush 5/16" BSF. [Ensure you drill it
square to the bush]
Drill
out the engine case thread with the 5/16"Dia. This is where the locating bolt
was originally fitted. [Again ensure that it is drilled square to the case]
Using a
new stud ensure that the tread is cut off, so that when it is screwed into the
bronze bush it is unable to touch the cam shaft its self.
Fit the
camshaft bush as you would normally do, then screw in the stud. This is a
little more of a fiddle BUT worth it.
Fit the
fibre washer, metal washer and then tighten the stud down with the nylock nut.
JOB Done !
You may
notice from the photograph below of the bronze bush that it has two grooves
around the body. Because I am using an up-rated pump I wanted to make sure that
no oil escaped between the bush and the aluminium housing. To seal the bush to
the housing I have used two ‘O’ rings.
The size
of the two ‘O’ rings is 1.25"ID X 0.125" Sec, the shore hardness value is 70~75
[quite soft].
No more
leaks or movement from the bronze bush.
This article, written by Mike Davies, originally appeared in CA7C Seven Focus
in Mar 2006 pp16-17.
