Reply to "Cam for 2V heads"

4V heads have very large ports. The intake, though overly large for most
applications, is shaped decently enough. Port stuffers can be used to raise
the dead flow region to yield an intake port similar to that of the Ford
Motorsport A3 racing head. The 4V exhaust was supposedly compromised to
clear the shock towers of early Mustangs and Cougars and has a hump then a
sharp drop with an exaggerated area change, though the 2V exhaust port clears
without all the weirdness. The 4V port exit area is very large but much of
it is wasted and the flow velocity low. The resulting poor intake to exhaust
flow ratio may benefit from a cam with additional duration (typically 6 to 8
degrees) and lift on the exhaust side, assuming a normally aspirated engine
with a typical street performance cam. As cam duration increases, the
reversion created by extra exhaust duration may actually become detrimental.
4V heads respond to a lot of lift and tighter lobe centers (108-110 for a high
performance street cam) and keep flowing more air past 0.600" valve lift.
The 4V exhaust port is sized for a 1 7/8" primary diameter header but you can
run 1 3/4" primaries if the flange is made correctly.

The 2V is a entirely different cylinder head, not just a 4V with smaller ports.
The oval ports, while small, are still decently sized. The intake ports are
biased to the side to get a straighter shot at the valve but have a poor short
side radius that is harder to improve than a 4V. Installing 4V intake valves
only make this worse. If going larger, a 2.08" intake should work fine.
The exhaust port has a moderate area change and a nice short side radius.
Though much smaller in cross-sectional exit area (though not necessarily a
smaller minimum area), the 2V exhaust port flows nearly as much as a 4V, with
substantially higher velocities. The 2V exhaust port is sized for a 1 3/4"
primary diameter header which. We've ported some 2V heads where the intake
flows 220 CFM and the exhaust 200 CFM. Since 2V heads such a strong exhaust,
they work well with a single pattern cam. Unported 2V heads tend to build
flow early (have good low lift flow) and level off after 0.530" lift or so.
Extreme lift cams will be wasted on 2V heads unless they have been ported.

Dan