whats the diff between 68 #5 heads and #5w31 heads is it just bigger valves and springs or was there port work whats the specs? also is a1970 4 bbl manifold(CAST IRON) and a w31 intake manifold the same design just the one is aluminum?

 

W-31s used the same head castings as all other 350s from the same year. The only difference is the valve sizes. You can machine any 350 head to take the larger valves, thus making it a "W-31" head.

The W-31 (and W-30) aluminum intakes were the same design as the cast iron. The only difference is the material.

 

do you know the valve sizes ? I think they were 1.9 something and 1.6 something

 

2.000/1.625

 

Thanks for the reply

 

Now that I didn't know, what a shame.