Cleveland Story Part 3

Okay, that was the easy part. Now we can look at different versions of the 351C. It is best to start out by describing how the Cleveland was designed for the Americans, before moving on to the Australians. Ford U.S. came up with two basic versions of their 351C, the 2V and the 4V. The 2V stands for, as it does most usually, 2 venturis, and describes a two barrelled carburettor. American 2V 351Clevelands came equipped with two barrelled carbs and as such the engine was designed to be the common version of the engine fitted to non performance cars. To this end, Ford U.S. designed a set of heads for the 2V that had smaller inlet and exhaust ports to promote better low down torque. These small port 2V heads required their own inlet and exhaust manifolds to mate up with the heads and they also had smaller valves. Initial rating of the 2V engine was 250hp.
The 4V was the performance version of the 351C, and was so named because it was designed to have a 4 venturi or four barrelled carburettor. To feed the extra fuel through the cylinders, the 4V heads had much larger ports than the 2V, and as result required their own matching inlet and exhaust manifolds, and larger valves. The combination of bigger, more effective 4 barrel carburettor, bigger valves and bigger ports ensured that the fuel mixture could get into and the exhaust gasses get out of the combustion chamber more effectively than in the 2V heads, hence the 4V engine would rev better and as a consequence, produce more power. The 351C 4V was rated, in 1970, at 300hp.
Engineering is often a compromise, and such was the case with the 4V. The valves, and especially the ports were so big that the inlet mixture could slow down in its passage into the combustion chamber. This decrease in velocity, most noticable at low revs, left the 4V versions of the 351C feeling kind of sluggish as the cylinders struggled to fill. The 2V, with its smaller ports and valves, could keep the mixture velocity up which promoted better cylinder filling, and gave the 2V its impression of greater low down power, torque and flexibility. Of course, this is what Ford U.S. wanted, promoting the 2V as the torquey grocery getter engine, and the 4V as the “let it rev and feel the power” engine.