to allow for adjustment bud,i used to love the ones you could adjusts with a spanner.....those were the days.shims give you more tolerance when cold which is better on colder start ups.......hence bag of spanners when cold
no no not the valve clearance shim but the shims under the valve SPRING seat into the head i just dont understand the point of them on such an agri/basic engine (no diss intended it is a great motor)
thanks it must be for valve spring length then as its under the spring seat but why? i see no gain by setting a valve spring down to 2thu and then compressing it to the length of the valve stem very odd