Reply to "2v or not 2v?"

all Panteras equipped with U.S. sourced engines were equipped with large port "4V" heads of 2 varieties, closed chamber heads rated for 10.7 to 1 compression ratio (which was actually about 9.5 to 1) and open chamber heads truthfully rated for 8.8 to 1 or 8.0 to 1 compression ratios.

Once the DeTomaso source of U.S. built engines dried up, they began sourcing 351C engines from Australia. I believe these were all equipped with small port 2V open chamber heads.

As Husker wrote, American Cleveland heads had a "2" or "4" cast into one of the corners. Australian heads do not have such a number cast into them.

The good 2V heads from Australia are sourced from the Australian 302 cubic inch Cleveland engine, the 302C, because they had "closed" combustion chambers. Not all Australian 2V heads have closed combustion chambers, only the ones from the 302C. The exhaust manifold flanges on these heads have a larger cast & machined area around the port, allowing 4V exhaust manifolds to bolt up with no leaks, the American 2V heads do not share this feature.

Don't confuse heads from a 302C with the C302 aluminum heads sold by Ford Motorsports in the '80s.

Closed combustion chamber heads, either 2V or 4V, will allow running higher compression ratios with out detonation, than that possible with the open chamber heads. However, closed combustion chamber heads also produce more hydrocarbon emissions, which may be a problem for Pantera owners who live in states that require them to smog their cars.

Keep in mind, the ports of the "small port" 2V heads are still quite large for a 351 cubic inch engine. I've witnessed "Chevy guys" on more than one occaision, upon seeing their first set of cleveland heads, 2V clevland heads at that, say "Wow, look at the size of those ports!" They think they are looking at the big port heads.

Small port heads, lets specify the 302C heads, flow very well up to about 0.500" intake valve lift, after which the intake flow curve flattens out (hits a wall!) They exhibit very good low lift intake flow. The exhaust port, though smaller than the port in the 4V head, flows just as well, making the balance between intake & exhaust flow better with the 2V head. With porting & big valves, these heads are capable of supporting about 500 bhp. The drawbacks are the lack of flow improvement above 0.500" valve lift and the tendency for power to flatten out at about 6500 rpm.

The advantage of these heads is throttle response. anyone running an Edelbrock Peformer intake & 600 cfm Holley on their 4V Cleveland to improve low rpm response, would be better off running the smaller port 2V heads. Racers needing improved throttle response coming out of corners also turn to these heads in classes allowing only factory cast iron heads. These heads work well with 377 cubic inch stroker motors too. Intake manifolds available for these heads include the Edelbrock Performer 2V (idle to 5500 rpm), a Ford oem cast iron 4 barrel carb manifold from Australia similar to the performer(idle to 6000 rpm), the Weiand Xcellerator (1500 to 7000 rpm), the Torq-Power which is a high rise dual plane manifold from Australia, the Parker Funnel Web also from Australia, and Edelbrock's soon to be released Air-Gap RPM manifold which is similar to the Torq-Power. Larry Stock sells Pantera exhaust headers for the 2V heads also.

Engine builder opinions vary from 400 bhp to 500 bhp regarding which point to switch from small port to big port heads, but below 400 bhp and below 6000 rpm there is no argument, you are better off with the 2V heads.

On the other hand, the 4V engine can be built, with the right combination of intake manifold, carb tuning, camshaft & exhaust that will idle decently, pull smooth & mellow at low rpm and then hit the meat of the powerband from 3000 to 7000 rpm. Stroker motors lower that powerband to about 2500 to 6500 rpm. The stroker motor also helps the throttle response of the big port heads.

George