The current issue dog nut locktab washer from Moss Motors part number 460-470 does not have an internal key tab to engage the pulley keyway, which seems to match original factory issue. This would appear to defeat the function of the lock tab, to prevent rotation, but there is a way to make it work.



The crankshaft pulley has a large milled indentation in the face of the hub near the center bore. And of course the pulley hub is keyed to the crankshaft.



The trick here is to install the locktab washer and the crank dog nut, tighten the nut securely, and bend up one edge of the washer against one flat on the nut. Then use a flat faced punch and hammer to drive the edge of the locktab firmly back into the indentation on the pulley to prevent the locktab from turning.

There are reports of some recent supply locktab washers being made with a center key tab which turns back into the pulley keyway. This type may be a little easier to use, if you can find one. BMC part number for the original pushrod engine locktab is 12A398.

Note that on the Twin Cam engine the crank pulley and dog nut lock tab are different, even though the dog nut itself is the same part.