Hello

 

I have a question.

 

You know how it is possible to bore out the cylinder displacement - Eg. 1300cc to a 1400cc - well, is possible to bore out the size of the valves? - (and replace with larger valves)

 

Just an idea...

 

(oh and the spelling fairy checker says theres no mistakes :D)

yes.

yes, most definately!

 

this is one of the best ways to get more air into a motor, and eventually becomes a must once you've gone as far as you can go with porting and manifolds. this is what you should do if you end up with a 3k bigport head, as the size of the ports is really too big for the size of the stock valves. that being said, then you need to fit different seat inserts, guides, seals retainers and possibly springs to suit the new valves, so it ends up becoming quite expensive, as there's alot of custom work involved

 

you can also go TOO big, the valve needs to be big enough to allow maximum airflow into the chamber, but small enough that it doesn't cause shrouding and restrict the airflow into the chamber. as a general rule, you should have 5mm @ half lift clearance to the edge of the combustion chamber. when you have an oversized piston, you can go a little bigger again with valves, as you can take the combustion chamber out further than a stock piston. we're talking miniscule amounts tho, 0.060" or 1.5mm at most. and if you do it all wrong and fit massive valves, you can end up with LESS power potential than a stock valve

 

http://www.google.com/search?q=bigger+valves

http://www.google.com/search?q=valve+shrouding

ahh ok cheers !

also gotta make sure you keep air flow velocity up. If the valves are too big the speed of the air will slow down and wont be optimal...