On Alfa number 15
AO Platinum Member
Join Date: Dec 2005
Location: United Kingdom
I have done belts with a Dial gauge to indicate TDC, and to be honest it is more difficult than using the marker on the lower cover.
There is a few degrees of movement at the crank pulley where the dial gauge will stay at TDC due to the dwell of the piston.
In an ideal world it would be better to use both, but if you haven't got a DTI then using the marker is fine.
The cam locking tools are an absolute must though, as the pulleys on the variator and the exhaust cam need to be loosened to allow the belt to tension correctly and evenly.
You will never be cool driving a Vauxhall.