My bet is not much if any. 21 is pretty good and likely very little will be realized by going higher. I've not seen any difference on mine.
My 2 cents on the blower...At your cruising speed of 55-60 mph that blower is making very little boost and thus takes very little power to turn, which means it adds very little heat load. Wide open throttle and 5000 rpm would be a whole different story.
Just my thoughts from 50 years of being in business as a mechanic and engine builder. Learned a lot the hard way for sure!
Terry (betting the old alum rad will fix it
)
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"It don't take but country smarts to solve the problem" (Smokey Yunick)
'41 Merc Town Sedan / 260" 8CM engine
'66 Fairlane four door / "warmed up"
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