Next time you are putting a motor together or just have a head off for a refresh, consider this little addition. It isn't difficult and can save a lot of head scratching later.
First you need to have a head off, and if no.1 cylinder is open, use that. If you only have the left head off, use number 6. As no.1's companion cylinder, it is at TDC at the same time.
Bolt a solid piece of metal across the centre of the cylinder. It has to be nice and strong. I used one of the brackets that came with my engine stand.
You then need to make up a simple pointer. You can get as inventive as you want, but I just bent something up from some scrap. I ground the end to a chisel point. Once the pointer is in place you carefully turn the crank in a clockwise direction and stop as the piston makes contact with the solid stop. Make a mark on the pulley in line with the pointer. This is a temporary mark, so I used some masking tape on the pulley so I could use a pen to make the mark.
Now you have to turn the crank almost one full turn anticlockwise until the piston comes into contact again with the stop. Make a second mark on the pulley.
Now you have to measure the distance between the marks and make a new mark half way between the first two. In my case this was easy as the marks were 40mm apart so I just made a mark at the 20mm point.
Then file a groove at that mark, as that is at TDC.
Remove the stop, take the tape off, stand back and congratulate yourself on how clever you are.
The whole job probably took probably less than a half hour.
A couple of notes: This works on a flathead because of the domed piston. For flat pistons, or any other type of engine you need a spacer of some sort on your solid stop to keep the piston below TDC.
Secondly, be careful when turning the motor over, because if your stop also goes across the valves, you could bend something. I didn't do this, but was wary of it.
Mart.