Whether buying new tappets or swapping parts about between engines it's worth noting an important detail difference beteen M and B models....
The B31/33 and M33 use the same tappet for both inlet and exhaust....Part No. 66-1493....This part is also used for the inlet tappet on M20 and M21 models...
However, the exhaust tappet on the M Series models is a different component...Part No. 66-1495...The reason for the number difference is that on sidevalve models the foot of the tappet is hard chrome plated to improve its durability, by helping it withstand the higher temperatures transmitted from the exhaust valve directly to the tappet...
Identifying features of this part are a slightly thicker 'lip' to the tappet head and the distinct whitish blue colour of the hard chrome plating on the operating surface...When compared to the inlet tappet the difference is quite obvious....No doubt the plated tappet could be run anywhere in any engine but the unplated one should be avoided for the exhaust side of the S.V. engines...Ian
I understood the finish to be hard chrome plating...However, that isn't the point of the post...It's just to highlight the differences so the correct parts are put in the correct location...Ian
