twin turbo heads
 

Ok i need to find out something about my heads there afr race heads 2.08/1.60 there cnc .Now someone tells me that i should polish then out to leave a mirror finish to then also my pistons??????? :willy:

The "mirror finish" thing is a myth that looks good on paper but yields very very little gain for the amount of labor involved.

GM found that they picked up NOTHING on the LS7 heads by polishing. They just left the CNC finish with the slight texture.

On the other hand it couldn't hurt if you are doing it yourself but I wouldn't pay to have it done.

Im no expert, this is just what I picked up from reading threads and talking to people.

I also read a deal about a slightly rough surface causing a "boundry effect" and actually flowing better than a smooth surface. That part is sorta fuzzy so some expert here can chime in. However, if you are making big time power then it might cause more of a gain.

steve is right i wouldn't do much on the intake side. if you do use a coarse sanding roll. the boundry effect has to do with wet flow only. you could polish the ext. side , and smooth the chamber a little , just don't polish it. depending on which afr head you have.(competition or race ready) there both cnc finished but one has a much finer program for the cutter toolpath . it wouldn't need much work at all. as far as the piston goes you can sandroll or blend the edges . just tape up the ring lands in case you slip.

Their is realy no gain in polished surface except to help carbon from sticking to the surface. We use 100-120 grit intake and a scottbrite fine finish of exhaust when hand porting