Wow. That is so stupid in so many ways.
First of all, it's just dumb. I mean, just look at these guys.

Second, those are not motors they have for heads, those are engines.
Third, a guy who's really into cars is called a "gearhead," not a "motorhead."
But most importantly, do you not know who IS called a motorhead? A speed freak.
Why do you think Lemmy chose the name "Motorhead" for his awesome amazing ass-kicking band? Because "Motorhead" was a slang term for an amphetamine abuser which Lemmy was. That's what "motorhead" means, not a person knowledgeable about motors.