quote:Originally posted by PANTERASHAH:
For a strictly street driven car with the motor operating between 2500-5000 rpms which is a better choice, 4V closed chamber heads or Aussie 2V closed chamber heads?
I have both 2V closed chamber and 4V closed chamber on almost identical 351c engines and i can tell you without a doubt that the 4V with the correct intake manifold and carb or injection setup will out perform the 2V, all other things being equal, in every way from 1000rpm up.
You would choose the 2V over the 4V if you were perhaps seeking to squeeze some extra MPG out of your car and your car was heavy. But there are not many MPGs in it.
The 2V of course has smaller ports and valves and also higher compression ratio so with a very heavy car the 2V may give you some extra throttle response at very slow RPM such as in city traffic and slowly plodding around the suburbs.
Although once the RPMs get up and with a lighter car like the Pantera the 4V heads as i say with the right intake setup should not have any appreciable throttle response difference to the 2V in a heavy car.
2V heads vs 4v heads tend to give the engine a different feel (character).
The 2V will give more of a linear feel to the engine eg: twice the RPM feels like it is twice as powerfull.
The 4v wll give more of a logarithmic feel to the engine eg: twice the RPM feels like it is four times as
powerful.
The choice depends on how brutal you want the car to be and how hard you drive it.