>warm her up and set timing by ear

I can't believe you are recommending this. Maybe someone who has timed the same vehicle 100 times might be able to do it, but in reality its nearly impossible.
Most people who set it by ear will advance the timing way too much. Since the idle keeps rising with more advance it 'seems' better. With the low stock compression it will not ping even if the timing is too far advanced by 10-15 degrees. I've seen cars that had 25-30 degrees of timing at idle!

Get a timing light and do it right!

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Csaba
1972 280SEL 4.5, silver