Timing

[Hedd_Jones]

How do you guys use the TDC measuring implements?. Ive always found that they dwell considerably at the top, that is they stop moving and you can turn the crank significantly before they move again. Getting an accurate TDC involves either skill or luck.

Spot on. 
The only way that you can find TDC with one is to interpolate from two equal levels of lift either side of TDC measured with a dial gauge on the top of the rod. It is however useful as a crude TDC finder for the "swing the dizzy" approach to timing.

I compared 2 approaches on my steam roller. I have the benefit of a crosshead to use for measurement.

I put some tape on the circumference of the flywheel, made a pointer and used a sharp pencil to mark.

I did similar on the crosshead and and guide, basically a pencil mark on each. Ligned them up and marked up the flywheel in 2 spots.

I then tried the DTI. I didn't need to draw any new marks, they were spot on. And this is on a flywheel approx 2 1/2 foot diameter. Any error would be less on a '7' sized flywheel. My conclusion was DTI not required.