You can bar over to tdc and take out distributor and look at the drive slot to see if it’s on compression stroke or not. If it’s 180 out the slot will be ever so slightly turned from being straight across. Turn over to tdc mark again and you should see the line be straight across.
I need to hear the logic behind this.
Just do the thumb over #1 plug hole as mentioned in previous answers. You can't possibly get it wrong,
The factory did it that way. When you build the engine, you drop the shaft in with the engine at tdc compression stroke. Anytime you put in a distributor after that, the tdc mark will get you where you need to go without any fuss. Simply rotate to tdc, look at slot. If straight across looking down the hole, you are at tdc of firing stroke. If 180 out, it will be slightly off from straight across. Once you see it both ways, you will never forget it.
This also creates a situation where the vacuum can sits where it needs to be and the plug wires route easily, because number one will be where it should be.
See what you learned today? Now you know, and knowing is half the battle.
