Lotus Elan and Lotus Elan Plus 2 Forums

I wonder were early S1 and s2 elan built using Whitworth BSW fasteners ? My English motorcycles of that period are all BSW

Nope. Look in the parts manual it shows the sizes of all the fasteners.

The Lotus alloy castings used BSP threads which have the Whitworth thread form and the plugs in these castings sometimes have Whitworth hex heads on them e.g. the diff drain and fill plug, But otherwise all the actual fasterners are UNF or UNC.

The Ford castings used NPT plugs and as the difference in thread form, TPI and diameter is small they are often confused

cheers
Rohan