[Fot] Finding TDC

[Mark York]

Amici,

I'm finally getting some time to finish the final assembly of my motor for
the TR3 racer, the machine shop did most of the work (pistons/sleeves,
crank, cam, and head), and I'm doing the rest. I called the machine shop to
ask how to find TDC since the flywheel has been replaced with a lightened
one and none of the indicator arrows are there, I was given the following:

1)       Rotate the engine until the #1 intake has just closed and the
exhaust valve is just opening (mark this position)

2)       Rotate the engine 360 degrees, this is approximately TDC.

Now here is where it gets a little weird:

3)       Weld a bolt to the bottom of a spark plug.

4)       Rotate the engine a quarter turn counter clockwise

5)       Install the spark plug / bolt

6)       Rotate the engine clockwise until the piston makes contact with the
bolt on the end of the spark plug, mark this point

7)       Rotate the engine counter clockwise until the piston again contacts
the bolt on the spark plug, mark this point.

The 2 points marked are approx 17 deg before TDC and after TDC. 

My questions are: how long should the bolt be on the end of the spark plug
(won't the length make a difference where the piston meets it)?  Does
somebody have an easier way?

The head is mounted and torqued, I really don't want to take it off. Doesn't
this process seem a little Rube Goldberg-ish? 

Confused in Seattle

Mark

 

PS: Thanks in advance