IMO, Ignore the marks and rotate it until the tang is correct.

3 hours ago, Zpat said:

Sorry to be so late to this party but this thread is very relevant as I recently pulled my distributor on my '72 240 and my oil pump shafts tang is in the exact 1:00 position as your original picture even though by all measurements I am at TDC (pistons at top, cam gear v notch lining up with thrust plate dash, cam lobes where they should be etc). I believe the gear oil pump shaft moved/slipped when I pulled my distributer. Could you give a quick outline of how you moved the tang back to the 11:30 position?

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i finally got it where it is supposed to be, and it fired right up. line up the marks as shown, turn the shaft a little clockwise?, then push it up in there. tighten one bolt finger tight and the take a look. it may take a few tries (you will be an expert shortly) but it will eventually go. very aggravating

 

Thanks all, sounds like just twist, turn, shove. If not correct, repeat until correct. Just wanted some direction as a chill went down my back when I saw sweatybettys first picture when the tang was at 1:00, identical to mine and hearing his earlier problems. I'm sure I will come back to the well if I have any problems. Happy motoring...

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i have narrowed my problem down to 2 cylinders mis-firing which Zed led me to.

the car is running now. i have put my timing light on every wire, and the light will work on all but # 1 & 3. i have switched wires around but no difference. new cap and rotor, no difference. i tried pulling #1 wire off the plug, and get a great spark to ground. im going to try new plugs tomorrow, any recommendations?

thanks all    sb

Seems like it would be the distributor that has a problem.  Wobble, bad points gap w worn cam?

54 minutes ago, 240260280 said:

Seems like it would be the distributor that has a problem.  Wobble, bad points gap w worn cam?

the distributor feels tight, no wobble that i can feel. im running pertronix ignition, so no points. i have turned the magnets several times with no difference

I've seen it proposed but haven't actually seen it - bad grounding of the spark plug body and threads to the head.  Several ways to test it or fix it, from vigorous cleaning of the threads to running a dedicated ground wire from the plug body to ground, or jamming a screwdriver between the plug and head.  You get the idea.  Seems far-fetched but fits the symptoms.

im thinking along those lines also. ill try the ground wire.

Maybe electronics are set for 4 cylinder rather than 6?

5 hours ago, 240260280 said:

Maybe electronics are set for 4 cylinder rather than 6?

there is nothing to set. pertronix ignition and factory tach.

12 hours ago, Zed Head said:

 Seems far-fetched but fits the symptoms.

Bad ground occurred to me too. It does seem far fetched but who knows...

Wires, cap & rotor don't change it, so: plugs or distributor/pertronix