I always torque the spark plugs by hand and always have an all my cars. Had some bad locations with some cars I've seen in the past...
However... Have you guys seen how many of the heads that people are selling get the "harmless" nice little cracks around the spark plug holes?
I know mine got them on the EJ205 engine that I sold.
I would like to avoid reducing the resale value of my heads and avoid forming these cracks..
I don't know if you guys noticed, but 90% of the heads that come up for sale have them and 90% of the people (rougly) torque plugs by hand.
I'll say this: the heads that come up for sale with no cracks sell for a nice premium.
For this reason alone, I'd like to calibrate my "handtorque" by using a wrench on at least one of the plugs.
I'm going to look at what the factory says to use for the plugs.