how much compression is raised by flat faced (not oversized) valves ?



When I researched, all people keep saying is "a bump up in compression"

I want to know a hard number.

thanks for your help
B

 

i think i read somewhere it was .2 but i dont know if thats total correct

 

raise about 0.3

 

First off, it will depend on what head you are using. When I called Supertech, their sales rep. told me on my GSR head, it would raise C.R. by about .005 per valve, therefore only a .08 increase in C.R.
In my opinion, the added weight isn't worth the minor increase in C.R. You're better off raising C.R. by utilizing better pistons.

 

It won't depend on what head you're using because cc's are cc's in whatever head you use. Decreasing the cc volume in any chamber will increase the compression by a set amount. .3 is the average for flat faced valves. FYI, a 2 layer headgasket is usually worth about .2 increase at a fraction of the cost.

 

and whats the weight differnce in stock valves and flat face valves

 

ive herd its around 0.3 but i'm no expert, i had blox high comp valves in a b16b head

 

Not enough to worry about.