Do diesel motors have tappets? What are tappets anyway?
A 4 stroke diesel engine will have what is commonly know as tappets, a 2 stroke diesel will not, these are not common in road vehicles. It’s a carry over from the old side valve engines. The tappet was a cam follower with an adjusting screw called the tappet screw, this also had a locknut the head of this screw was directly below the head of the valve and was where you set you “Tappet Clearance”. It was fairly common years ago for cam followers to be called “tappets” on side valve, overhead valve and overhead cam engines. What we refere to as “setting tappets” is in fact “setting valve clearances” To ensure my answer was correct I’ve consulted “Q&A on Automobile Engines, Published by Newenes in 1965. A tappet is the cylindrical component that transmits the motion of the camshaft to the valve, there may also be a push rod and a rocker arm between the tappet and the valve that further transmits that motion. On an engine where the rocker arms act directly on the camshaft they do not have
There is little difference between petrol or diesel other than one uses compression ignition and the other electronic timed spark ignition , the diesel engine is more robust because of the pressures exerted but both had tappets before the advent of overhead camshafts which are on all but a very few models now as overhead cams are more efficient , the tappets function is to open the inlet valve to allow induction of fuel and exhaust to allow the engine to expel the exhaust gases . the tappet (or rockers) worked from a revolving cam pushing a long rod up to the cylinder head were they were situated and pressing each valve down in a timed sequence.
