In terms of power difference what are the stages in terms of power?
Is a standard inlet is 24mm? good for how much power?
Then you get polished versions.. good for how much power?
Then opened up to 25mm? good for how much power?
Whats next?

This is mine:- measures 25mm top to bottom and is very polished and smooth and my inlet manifold has been matched to it

 

i'd like to know the answer to this one too...

 

me 2 as i need to know soon

 

will let you know once my car is back on the rollers

ive changed my standard head for 26 inlet and 25 exhaust porting

 

noone else knows then

 

IIRC 25mm/25mm ports equate to flow potential for 500-540bhp and 26mm/25mm are good for 600bhp+.

 

Cheers

 

That head looks identical to mine which was done for a 450ish build.

The finish looks rough on photos (more so with flash) but is very smooth to touch. The web between the ports is also very sharp.

Interested in the comments you get as no one seems to want to talk about heads or divuldge specs

 

Is it that simple as putting set limits as there is so much else to consider with turbo, cams, manifolds etc? I remember seeing over 420 @ wheels on a standard head and cams before.