If you put a straight edge / Ruler across the spindles at the bottom of the threads,
That could give you an idea if one is a lot lower than the others,
You can easy draw out a spindle if too far in, With washers and a nut,
You should have to warm up the cases , But most are not very tight,
You will only feel the end float on cams and followers if the pushrods are removed,
Be very careful putting the pushrods back in, It's easy to miss the / Location cup in the top of the follower !!,
Looks to me like someone has been in there , Not very long ago ?, And fitted a steel Big idler ?,
They had Alloy ones in the early days which were not good.
Have you any Vincent Owners nearby who could maybe help ?.
I don't think you have the right thrust washers on the camshafts ?,
On the outside There should be one that just ! goes over the thick bit of the shaft,
Then a small one that goes at the base of the thread before the alloy plate goes on ,
Be careful when you put the alloy plate on the bigger one can move away and drop down
Between the end of the thread and the small washer !!,
Which will mess up your end float,
I am afraid the Timing side is not the best bit on a Vincent,
But can work well if you get it right.
Good Luck, Bill.