Does switching to bigger exhaust valves kill velocity?

Discussion in 'Fox 5.0 Mustang Tech' started by Highbredcloud, Dec 16, 2003.

  1. Just a questions for people who know stuff about heads...Does switching to a bigger exhaust valve kill velocity in any way? or is that with a bigger intake valve that velocity might be a problem. How does switching to bigger valves on an unported head influence the changes over stock? I have a set of GT-40X heads and the intake valve is 1.94 and the exhaust is 1.54...Just curious if I would run into any porblems if I switched the exhaust valve to a 1.60 on an out of the box head. Please let me know.

    BTW: I would use something along the lines of an E-cam or some other emmision legal cam for the heads.

  2. Just switching the valves wont do anything... you need a new valve job aswell.
    On the exhaust you will see less of gain from going to a bigger valve than on the intake. But on a box stock head, any bigger valve than what you have already isnt going to help without porting to open up the venturi and or whatever else in the choke point in the port. It will only add more weight to your valvetrain.
  3. So you can't just put bigger exhaust valves without porting...right? How reliable would that make the car assuming everything else is emmision legal? Thanks for the info. :nice:
  4. Sure.... you can put bigger ones in, but it wont make a difference unless thats what was holding you back.