Originally Posted by
66f-100
Maybe the heads are just ported differently on the 390. The engine builder showed me the difference in port sizes between the two and the 390 ports were significantly larger. The heads were Ford heads, not aftermarket.
I never said one word about the heads being aftermarket.
How many different FE heads were used from 1958 thru 1976? Dozens!
Which heads does your truck have? I haven't a clue, I do know what was there as original, but...
After 40 + years have passed by, who knows which heads are on the engine now?
And, who knows after 40 + years have passed by, if heads were ported and polished sometime in the past?