906 heads casting letter F

[pro-streeter]

does anyone know what the casting letter indicates on the 906 heads?
The letter I’m referring to is on the chamber side of the head at intake parts. I have one set with F and one set with R.

 

[GTX JOHN]

We have flow tested every different 906 heads AND
the F casting are the highest 906 flowing heads.

The C heads are the next best flowing.

Both are worth hoarding or using especially on a S
tock Eliminator car.

There are things that you can do to bring the other ones up to similar
flow in Stock but of course no one does that ever.

 

[pro-streeter]

Wow
Thanks for the information.