Bigger valves?

[Alxsmt]

im debating wether i want to get bigger valves for my 3400. how big is too big? BTW there 3500 heads and top end with the 1393 cam regrind, flat top pistons (9.8:1) this is an NA build too

ive heard that going to big i can hurt perfomrance

[geoffinbc]

Well the stock valves are not too big. And it would be nice to go bigger. But the physical size of the head, the valve layout and their orientation to each other are going to limit the face size. You might be able to go a few thousands bigger and it should be quite easy. The gains may be negligable though.

[Joseph Upson]

Three angle valve job and a good mild port and polish would probably be a better mod. Increased flow with larger valves is only necessary if you intend to push the top end up with a cam. From what I read resently unless you know you are dealing with restrictive heads the valve size is pretty desently matched for the displacement and cam from the factory. I had been pondering the thought for my 3900 heads but the cost compared to the gain wasn't attractive enough on desktop dyno.

You have already upgraded the engine by going to the better flowing 3500 heads.

[Alxsmt]

ok thanks guys! i might just save my money for something else then

[geoffinbc]

From what i have read stock valves use a 4 angle valve job. Dont make it worse by going with a 3 angle.

[ignoreance]

Ben (SappySE107) has tested different valve sizes in the 3400 heads. He replied to a post I had about flow increase on larger valves. But my question was on the iron heads which he wasn't able to give me a diffinitive answer on. Just send ben your heads and have him do it up threw the store. He sounds like he knows what he is doing. http://www.60degreev6.com/store/ err umm I don't know if he has tested the valves in the 3500 sorry reason for edit