you can go with bigger valves, in fact the Patriot stage 3 heads claim that the intake valve is so large that you can only use it on a block that's been overbored. i called them up an asked them about it and the guy i talked to claimed that without that .015" extra clearance (from a .030" overbore) that the intake valve will come in contact with the engine block, so that's one factor that limits the size of the valves. and the picture below is from Patriot's web site that shows the underside of a 2v cylinder head, and it looks like the combustion chamber itself limits the size of the valves, otherwise you'd have to increase combustion chamber volume, and you still might have a valve come in contact with the block.

 

looking at that makes me crindge, that combustion chamber doesnt look efficient to me.

 

and in no case is overboring to gain clearance for bigger valves a good stand point for performance because that just goes to show how shrouded the valves are.

 

Thats exactly what I was thinking.

No matter how big you go on the valves, its just not a well designed head from CFM point of view.

I swear, WHERE are the companys for our 4.6 2v??? I simply do not understand how there is not an aftermarket head for the 2v yet, consdiering the sheer volume of 4.6L 2v out there (think of it... 96-04 mustang GT, early Tbird 4.6, truck 4.6).

The first person that comes up with a 275+ CFM aftermarket head that can be CNC for more will be a multi millionare... and have at least some of my money too.

 

I'm on the same page! WTF, how can they not see how much they would sell? Well I'll tell you one thing, if there isn't a set of aftermarket heads by the time I finish my engineering degree. Well then, there will be. Hopefully I can make my first millions!

 

Hey guys. Im new to this forum and wanted you guys take on what motor i should use. I have a 2001 mustang gt stock as a rock. I have decided to go with either turbos or a procharger. I have heard a lot about swapping in a 5.4 2v and was wondering what you guys think. All im looking for is 600 rwhp on pump gas. I will also have a set of fox lake stage 3 2v heads and the cams have yet to be determined because i havnt made up my mind to go blower or turbo. Any help would be great.

 

i dont know if i was bull****ed but some guy around town is saying his mustang has a big bore kit and like a lot of money into the motor so hes pushing 600+ rwhp all motor. i didnt believe him but i gave him the benefit of the doubt

 

while we are still on this topic

what is the most you can bore the 4.6? 5.1ish?

and what if you were to stroke and bore?