WHEN CARS GET ROUGH

NZ Truth, Issue 1175, 7 June 1928, Page 15

WHEN CARS GET ROUGH

Valves Usually Cause of Noise fi''''i'm'i'!'''i"''t!"im!'i'ii'im"""" '""""" '■"'"■ii>'»»iririiiiipiuniii!itiniiirnriiiiiiiiiiiii>tiiiiiiutiniinii>uiiiiiiitiiniiiniriiiiniiit tiiiiitiiiiiMiiriiiiiiiMiiTiiiiiiiMiiiiiiiiiinniimiiiiiiiitiiti'^ || an engine, previously well behaved, seems to get "rough" and ji || to be incapable of idling regularly, or when it seems to stagger g| || about under a light load, or to get unduly hot, it may be taken almost || II for granted that the valves require attention. • ' || | p^^ „„„„„„„„„„„„„„„„„„„„„„„ „„„„„„„„„„„ ,„„„„„„ ,„ „,„„„„„„„„„„„„„„„ . v X |f > HNI»'MtMMMMHtIHIMMMHHHMHIHI>ItIIIIHMHHIH>HIHIMIMMt)HtMIH)HHHIHHII tII II IIItII M I ' I "I "

OFTEN with new engines, after some running, valves make a great deal of noise and clatter. That is due to the settling down m their seats, and the settling down of the tappets and gear, all of which means an accumulation of lost motion before the valve commences to be raised off its seat. This means, also, a reduction of the amount of gas-way through the valve and a re.duction of the i amount of gas which may be drawn through it, m the case of the inlet valve, or an obstruction to the outgoing exhaust gases m the case of the exhaust valve. In both cases, engine balance will be upset, overheating may take place, the efficiency of the engine will be reduced, and engine balance may be seriously affected. • The engine will not feel like its old self, and the performance of the car on the road will be materially, altered — and for the worse. It is well to have a piece of thin, hard

steel, such as a safety razor blade, which can be kept as a guage to verify the clearance between the end of the valve tappet or plunger and the end of the valve stem. In the case of the overhead-valved engine the gauge will be used between the top of the valve .stem and the underside of the rocker lever which operates it. It is important thai the clearance between these parts, when the plunger is free of the cam, should be the same for all inlets and all exhausts, and it should be just 'sufficient to ensure their not touching when the engine is hot, or when it is cold, according to the maker's instructions. It is not an easy adjustment to make accurately, because it quite often occurs that, when locking the nut back on the threaded part of the plunger, the latter is drawn farther out. A sequence of tests, with, a careful gauging after each' locking-up, is the only way to ensure precision.