Like the title states, is getting +.5mm bigger needed for 500-600? The valves I'm buying are out of stock for standard size but they have +.5mm in stock.

 

My plans when I get head work done is to get .5mm oversize valves with my setup. IMO, they're perfect for 500-600whp.

 

stock valves and head flowed 220cfm @ 0.400" on a superflow 1020.
mild Porting, Newen CNC valve job and stock sized valves flowed 260cfm @ 0.400" on the same bench.
1mm oversize valves on the stock seat LOST flow

 

Stock valves haven't been found to be a restriction up to about 1000whp. I forget where, but there was a big debate on this.

 

unless you plan on making 4 digits of power, you dont need them.

 

So do you think going +.5 is pointless? And I thought pushing over 1000, you need to have 1mm to notice a difference. How is .5 for over 1000? Shouldn't the limit on .5 be less?
Has anyone done any testing with +.5? I've only seen +1mm size but never any +.5.

 

any size valve not std size is not needed unless your going 1000 plus

 

What shop is going to do the porting, and what cams will you be running? What are your HP goals.

 

This local shop around my area that did good work to my block. Cams, I'm still deciding but most likely GSC S2 or Kelford 272. HP is somewhere between 500-600.

 

i wanna know more about this, or should i just stay with my stock Valves?
MIKE