Positive stop – obtain an old spark plug for the Ford engine – most of us have at least one laying around. Put it in your vice, and with tool of destruction you deem appropriate – cut off the ground tip and bust up the ceramic around the center electrode. Keep pounding to get the ceramic and center electrode removed so you’ve got a good ¾” or so of hollow space inside what used to be the ‘business’ end of the spark plug. If you happen to break the ceramic on the part that is exposed when the spark plug is installed, don’t worry about it. Once you’ve got a nice hollow space in the tip of the plug, take a 5/16” tap, and cut threads inside that end of the plug. I found that diameter to go right in without any drilling required. Once you’ve cut threads, insert a bolt about 1.5” to 2” long, and screw it into the threads you just cut. Then take your hack saw and cut the head off the bolt. Wouldn’t hurt to take your file and dress up the freshly cut surface so no sharp edges or shrapnel enter the combustion chamber. Also clean up the threads on the plug so that it easily screws into and out of the plug hole.
Determining TDC with head on – assumes new cam is in place with gear set 'dot to dot', all rockers are off. Place socket/wrench on the harmonic balancer bolt and rotate engine so that the piston will be slightly down in the bore. Unscrew the spark plug in that cylinder, and replace it with the positive stop you just made. Only screw the positive stop in hand tight – be sure your bolt isn't too long, you don’t want to jam it into the cylinder wall on the opposite side. Install your cam degree wheel and pointer. You may want to remove all spark plugs at this point because it will make it easier to smoothly turn the engine over in small increments. GENTLY rotate the engine clockwise until the piston comes to rest against the stop. Note the degree wheel reading. GENTLY rotate the engine in the opposite direction until the piston comes to rest against the stop again. Note the degree wheel reading. TDC is exactly half way between these readings. Calculate where that position is on the degree wheel, remove the piston stop from the cylinder, and rotate the engine to TDC as you calculated it. Make note of the reading as this is the base from which you will take all your readings.
Now simply set up your dial indicator on the number 1 intake lifter or pushrod, and see where (crankshaft degrees relative to TDC) .050" lift actually occurs. For example, if the cam card says .050" lift should happen at 5 degrees BTDC, and your measurements indicate that it's occurring at 7 degrees BTDC installed dot to dot, then you're 2 degrees off - in the advanced direction (the intake is opening 2 degrees earlier than the cam card says it should). So you'll have to retard the cam by 2 degrees to move it from 7 to 5. You'd pull the gearset off, and re-install using the "2R" slot, and then re-measure to be certain you've hit .050" lift at 5 degrees BTDC as the cam card calls for.