We have 79 F150 with 351C 2V. Heads have been sent away for porting, we have pop up pistons Seal Power #L2348F30 not sure if we put 4V valves in if they will Hit the piston. Or is it even worth it to go with 4V Bigger Valves?

 

some say some say no, i don't think i'd go the full jump to 4V size valves. the short turn radius in the 2V head and the port size doesn't support the flow of a valve that big. i'd save the meat in the seats for a long lifespan of the heads. you can use a slightly oversized valve to reach outward to fresh material if/when your seats get used up, if you hog out to 4V that material is gone

 

Like I mentioned in my earlier post the guy who built my engines used 2.11 and 1.69 valves. He has been messing with 335 series small blocks since they were new and after years of experimenting on the flow bench he found these to be the best fit for the 2V heads he ported. The valves are out of a Pontiac or Buick 455 I can't remember which, but the stem diameter it right and I think he shaved off the top a little to keep the valve train geometery correct. Unless you plan on a lot of port work you wouldn't even want these valves. You have to be careful nowadays because you can easily get more money in a set of iron heads as a set of aftermarket aluminum heads will set you back. I did my motor 10 years ago so the aftermarket heads weren't around and even the aussies were not around and very expensive if you could find them.
-Johnboy