Just curious how much compression flat valves add? Is it like .1 or something, or a lot more?

Please let me know ASAP, it is all I can get my hands on and have a big boost car.

 

Honestly, it depends on the application.

For example, if you had a single cylinder, single valve engine with 4cc combustion chamber volume at TDC and 40cc at BDC (10:1 compression) with normal valves in it and you put in flat valves that cut 1cc out of the volume of the combustion chamber, you'd now have 3cc at TDC and 39cc at BDC. This works out to a 13:1 compression ratio. Put the same valve in a 5cc combustion chamber engine that is 50cc at BDC, reducing it to 4cc and 49cc, and compression bumped from 10:1 to 12.5:1.

These are obviously exaggerated examples, but I'd say your best bet is to either call the company that makes the valves or determine your combustion chamber volume and bust out a pencil and some paper.

 

How about on a D or B series engine? Lets say it starts as 9:1? Is this a BAD BAD idea?


Modified by Project-D at 10:28 PM 8/5/2006

 

figure .15-1 increase in compression ratio over dished valves in the same motor.

 

Fantastic... That is the information that I was looking for. Thanks Earl!