For reference: simple test tool for verifying TDC position

[Dakota]

Now that my Challenger is in dry dock for the winter, there was time to knock off an item from my "to do" list:   verifying whether the zero mark on my timing chain cover scale actually represented TDC.   It turns out it didn't, but it wasn't off much.    The actual TDC was at 1.5 degrees before top dead center on the scale.  I'll adjust the distributor position accordingly when I run the motor in the spring as my goal is 34 degrees "all in" timing.

I used a "TDC Checker" similar to the Proform 66792 Top Dead Center Locator pictured below.   This tool is placed in the #1 cylinder spark plug hole.  The process for using the tool involves rotating the crank with a ratchet until the #1 cylinder piston gently contacts the bottom of the tool, marking that position on the balancer, rotating the engine in the opposite direction until the piston again makes contact with the tool, and then marking that position.   TDC is the midpoint between these two marks.   

There are a bunch of YouTube videos about this process, including this one from Summit Racing:

https://www.youtube.com/watch?v=RENhHI9n65I

I elected to take out all of the spark plugs to make it easier to rotate the crank (I wanted to check the plugs anyways).   An MSD timing tape is already on my harmonic balancer, so I used the numbers off the tape to measure instead of marking the balancer.  Ideally, this check should be done before the engine is installed or at least before the fan is in place, because otherwise you'll get to rotate the engine from underneath the car which gives you extra opportunities to test your ability to overcome gravity.