This is one area where the "high port" Cleveland heads is superior to the original Ford iron head exhaust port configuration which turns them down. The 2v ports simply can't be made to flow equal to the 4v ports in any configuration.
The 2v iron head is worse then the iron 4v in that respect.
That's one reason why the 3v heads, 2v intakes with 4v exhausts are popular.
I'm a little baffled by this. I've been hearing for years that the 2v exhaust port actually flowed better than the 4v exhaust port. The opposite of what you are saying.
4V heads flow better without a doubt! As Doug pointed out, 2V heads are purported to make more low end torque and offer snappier throttle response and off idle performance in a street driven Cleveland because the smaller intake ports allow for higher air/fuel mixture velocity at lower RPM's. But 2V heads will not outflow 4V heads!
posted August 30, 2009
The 4V exhaust port is an oddity of the Cleveland design, something we uninformed masses will scratch our heads about forever. Consider that the 2V head was an afterthought, it was designed by the same engineers who designed the 4V head but it has no gas bounce trickery in the exhaust port. The 2V exhaust port out-flows the 4V exhaust port measured in the conventional manner on a flow bench. But the 2V head does not have the same potential as the 4V head. I think the flow bench is a good tool for measuring the results of porting work, or for comparing one head to another, but it does not measure the head under dynamic conditions, with a piston going up and down in the cylinder, valves opening and closing, and combustion taking place etc etc. The engineers at Ford had dynamic potential in mind when they designed the 4V intake and exhaust ports. I guess the exhaust port design just didn't pan out as well as the intake port in real world use.
So which exhaust port flows better ??