Here's a picture showing the TDC mark and the 28 degree mark on a T4 fan. The TDC mark is close to the seam of the case, the full advance mark is to the right, one blade before the rib. All 1.7 and 2.0 914s are timed using this mark, engine at operating temperature, hoses off and plugged, at around 3000 RPM. This photo is for illustration purposes; ignore the junk oil filter and the POS 009 distributor.
The Cap'n