doing head mods and looking at putting bigger valves in. had a look around the site but couldnt find anything. i know the discussion has come up before but it alludes me. for those that know, what is the go with mild re-sizing? i know l series valves go in but i understand this is mild. is there something bigger that is not too exstravigant? its for a turbo motor. a15

cheers

1mm bigger what head are you running ?

standard oval port with 1.55 lift ratio rolla rockers. proably wont do much port work as it will run 20-30psi boost. just clean up the runners

just a slight deviation, but still relevant
Will a turboed motor benefit the same as a NA motor from porting?

I was under the impression that the quicker/more that you get it in and out the better.

Quote:

Hell yeah forced motors love porting.
Remember that boost pressure is only a measure of the resistance to the flow between the pump and the head of the valve.
If you reduce the impeadence to the flow, (ie better porting, bigger valves) then more volume of air can enter the cylinder, with less boost pressure being created. Less pressure=less heat=greater charge density=MORE POWER
Some say that too big a ports can increase lag, less of an issue though with a correctly sized turbo. I don't think this would be an issue though with the port volume increases that can be acheived with an A series motor. Especially if the porting is done by a pro, who is working to increase the flow.