Hole in #6 cylinder combustion chamber?

[plym_46]

You can also crank the engine manually and measure the stroke of your engine if your not sure what you have, 218 or 230.

[TodFitch]

It is used to check the valve timing: Place a long stiff rod in the hole and use a dial indicator on the rod to determine when the piston is at TDC (#6 cylinder and #1 cylinder are on the same "throw" of the crank so they are both up at the same time).

If you can't find the ignition timing marks on the flywheel (early models) or belt pulley/impulse neutralizer (later cars) you can us the above method for static timing of the ignition too.

[Phred]

What is the hole above the #6 piston on all flathead sixes for? It is plugged from the top of the head.
Why is the hole there?

Thanks in advance