The International Cessna^® 170 Association

I have a C-145-2 with a undampend crank (with hole). After a careful search with a magnifying glass, I found the TC mark on the prop flange. As hard as I looked I could not find any other timing marks specifically 26° and 28° BTDC for mag timing. Are these marks supposed to be on the crank?

I couldn't find any on my flange.... (are they supposed to be there?).

We used a propeller protractor and put strips of tape on the spinner
and cowling. Then we used a felt pen to mark off the 26 and 28 degree marks on the tape to check the timing.

Bela P. Havasreti
'54 C-170B N170BP

A timing protractor is what was commonly (and intended to be) used for this job. Some of the cranks have only the TC mark, but most also have a small index-scale marked with the 26/28 degree points marked. In all cases, the darn thing is hard to accurately place into position to set the points in the mags unless a protractor is used. (It can be done, but with difficulty. Many mechanics use a dental mirror to reach around behind the spinner backing plate to align the marks with the crankcase split.)

So as difficult as setting the timing correctly ie 26 and 28 BTDC in the REAL WORLD how accurate must one be when setting the timing of the mags to get the engine to perform right.
I know the FAA correct answer is exactly 26 and 28 degress BTDC.

I know some guys that usually bump the timing a bit-- that is,set it on the early (advanced) side of the specified setting by maybe a degree. I set mine right on the money,though.

Eric