ADJUSTING OVERHEAD VALVES

Dominion, Volume 30, Issue 254, 23 July 1937, Page 15

ADJUSTING OVERHEAD VALVES

There are still many cars of popular make fitted with push rod operated overhead valves. These have the-ad-vantage of being very accessible for adjustment, but have been criticised for an alleged tendency to become noisy as wear develops in the various moving parte There was some truth in this charge years ago, but manufacturing methods have since changed, and there are any number of o.h.v. models in use which have covered 30,000 or 40,000 miles, which are no more noisy than their side valve contemporaries.

It is true, however, that o.h.v. engines need rather wider clearances between valve stems and tappets than side valve engines, and motorists whose experience has been confined to the side valve type should remember this if they have changed over to the overhead valve. Generally speaking, the clearance required by overhead valves is .OOGin. for the inlets and .013 in. for the exhaust.

Wider clearances than this are quite permissible, provided they do not make the valves too noisy in operation, but closer settings are not wise. Incidentally, because of the comparatively big expansion of the push rods, valve settings should never be made unless the engine is at its ordinary operating heat. This is even more important for o.h.v. units than for the side valve type.