Grafhex Lens 135mm with flash ?

Boy its been several six years since I used the flash with this 3x4... want to verify.. the flash selector, on bottom of lens has four settings..
OFF
0
8
20

Please verify for me, that these are the delay settings for the different old flash bulbs..
So using a modern Vivitar flash, I set this to "0".

Correct?

You can test the flash synch simply by pointing the flash at the lens and viewing through it from the reverse side while firing the flash. You will see if it sychs at the different settings. If you can see the flash fire while you view it through the lens then you are ok.

Yep... thank you

0 is for electronic flash, which needs no headstart to get burning, as flashbulbs do. When the shutter is open, the flash is fired.

8 and 20 are for different types of flash bulbs. Fire, as in flash bulbs, takes some time to reach it's maximum. If I remember correctly, the later small wire-filled bulbs need to be fired about 16/1000 second ahead of shutter full opening, the larger bulbs need around 20/1000 (the 20 on your lens), and gas filled bulbs were in the 5/1000 range, which is probably what the 8 is for.

Mdarnton is correct that the numbers are the millisecond delay between flash contact and shutter actuation. 20 milliseconds is the delay for the type M bulbs - number 5, 25 for example.