So is there anyone who has actually done a leakdown test and can comment on whether it is necessary to lock the engine somehow? I can't see how you can get each cylinder at exactly tdc and then apply 100+psi - the engine position will be out by a little & the engine will rotate - that's what I think - but i've never tried it.

Has anyone tried it ? Do you have to fiddle for hours getting 'exact' tdc - or am I making a lot of fuss about nothing!

Steve