PRC CNC'd Heads
 

Hi everyone. I have a question about a used set of heads that I bought. These are a set of CNC ported 799's by PRC. Is it common that only the top parts of the intake runners to be ported? It seems like the bottom halves are uneven and below some sort of "plane" as to where the rough castings did not get CNC'd. Thanks!

Jody

True. Flow is mostly affected by the upper half of the port; which is why the floor of the port is usually not touched, as lowering the floor is actually detrimental to flow.

I seen something similar when I had 799 heads ported by TEA. Some of the casting wasn't completely cleaned up and it will probably vary slightly from casting to casting.

If it bothers you get a "Tootsie Roll" die grinder and polish them up...

There are too many irregularities in the casting process. CNCing heads gives you a repeatable flow from port to port - sometimes raw parts of the casting are left behind because they are inside/outside the CNC program.

In short, it doesn't matter.

My PRC exhaust ports were only partially ported. The heads work great.

Basically, material is removed ONLY where it needs removing. Makes sense to me!