I'm just putting the camshaft in my A65 (67 Spitfire). The parts book shows a peg Pt No 40-28. What does it do and where does it fit?I have the rotary valve driven with tangs driven from the camshaft. there seems nowhere to fit the pin. Help.

The peg fits into the cases and retains a plate with 2 windows (the plate has a cut out for the pin) I’d be surprised if either were missing from the crank case.

... mostly just repeating what Alan said ,
If you did not replace the bush ... its probably already installed .
Its the plate retainer pin ...for this part ... the stationary plate .
That lives at the bottom of the drive side bush .

Thanks for the info. Allen and Quinten. Bush and plate still in situ so should still be there.