what would flow better? a set of vortecs or a pair of older gm castings like 920, 441, 487 336 or 993 that have been ported....ported alot

 

ttt

 

The problem with most of the head castings you listed is that they are poorly done, usualy core shifted, and fairly light for material in critical areas. I've ported some '993s with decent success, but the castings had to be good to begin with. I've had better success with the later '416 castings. The '441s might not be that bad either, but again, make sure the mold cores weren't badly shifted during casting so that the runners and jackets have adequate thickness when you're finished. Some '441s were used on the early '70s LT-1s and had 2.02/1.60 valves.

In any event, all the heads you listed have 75-76cc chambers. Compared to Vortecs, your final static compression is going to be substantially lower with them. If you're planning to run NA, that might not be the most efficient with large chambers and flat pistons.

 

I agree with Vader. If you're going to port a common chevy head
start with a small chamber head, like a 305 performance head (416, 081) With full porting and bigger valves they really come alive.
You'll get a decent compression ratio with float tops on a 350, where a 920/441/993 will be down 1 compression ratio.

The vortecs are hard to beat thou. great performance.

 

My vote is the vortecs. They are a better design altogether. They are newer and easier to find uncracked. You may even find some with little or no miles so you can just bolt them on without any machine work. I have used vortecs for about 2 1/2 years and have been impressed from the time I bolted them on. I know a guy that just put a set on a 350 with a .480 lift cam and he is very satisfied. His engine is in a S10.