ADJUSTMENT TO VALVES.

Ashburton Guardian, Volume 59, Issue 22, 5 November 1938, Page 9

ADJUSTMENT TO VALVES.

GREAT IMPORTANCE. When the owner who likes to do most of the simpler mechanical jobs on' his car himself, sets about tuning the engine along the lines laid down in. the car’s instruction book, he should remember that the first step must be to check the operation find adjustment of the valves. This is a. point that often is overlooked, but a. little reflection will show the wisdom, of it. The valves control the admission of the mixture to the cylinders and the expulsion of tae buynt gases, and any faults in their adjustment or anything which prevents their correct operation will so upset the normal, even firing of the mixture in the cylinders that any attempt to tune the engine by careful adjustment of the ignition and carburetter will be nullified.

Presuming that the combustion chambers and valve faces are reasonably clean and that the valves are capable of seating well, there are two things which can upset their efficient operation, first, faulty tappet adjustment, in which one or more of the tappets are set so high that the valves they operate cannot close properly, or, alternatively, set so loosely that valve opening is delayed; and, secondly, a collection of gummy matter on the valve stems from a. combination of carbon and burnt oil, which makes some of the valves stick in their guides so that they do not close.

If it is suspected that one or more of the valves are sticking in this manner, remove the valve tappet cover, and. with the engine idling, watch trie operation of the valve stems. The offenders will soon be seen and steps can be taken to cure the trouble. Squirting kerosene on the valve sterns while the engine is idling usually is effective in washing away the deposits which are the cause of the trouble, alhough, for obvious reasons, it is .far easier to apply their cure to an overhead valve engine than to one of the side valve type. Occasionally; there will'be- an engine in which this trouble is chronic, and in a case of this sort the {regular use of an upper cylinder lubricant will keep the valve stems properly lubricated and free gum mi ness that sticks them in the guides. Actually upper cylinder lubricants are so good in any engine that their constant use, whether the ear ever has been troubled in this manner oiv not, is an insurance that it, never will happen. 1 The actual clearance between the valve tappets and the valve steins must always lie cheeked, when the engine is at normal running temperatun'. It will be necessary occasionally to turn the engine over by hand to bring the tappets in turn, clear of their cams, and the clearances must bo cheeked with feeler gauges of the proper size; guesswork in this case is not permissible in a modern engine.