Reply to "351C heads"

panhe,

I'll answer your question about the oem Cleveland heads first. The difference between 2V & 4V heads is the size of the ports. The 2V ports are very big, compared to those in the heads of competing American engines (small block Chevy, small block Mopar). The 4V ports are enormous. Ford was in a bigger is better mode in the '60s. As racing has progressed, the size of the ports in the Cleveland racing heads grew smaller & smaller, as the racing community learned that port shape & gas velocity were more important than size alone. The basic design of the Cleveland cylinder head is excellent however & was copied by Chevy for their NASCAR engines in the '90s, and my understanding is the latest generation Corvette has cylinder heads that incorporate features of the Cleveland cylinder head design.

Cast iron Cleveland cylinder heads manufactured by Ford come in 5 flavors, the variations being the size of the ports, the size of the valves and the shape & size of the combustion chamber. The '70 - '71 351C4V had big port heads, with big valves and "closed" combustion chambers. The '72 351 CJ (cobra jet) had big ports, big valves and "open" combustion chambers. The '73 - '74 351C 4V had big ports, smaller valves and open combustion chambers. The 351C 2V engine, not used in the Pantera, had small ports, smaller valves and open combustion chambers. Over in Australia, a smaller displacement Cleveland engine was in production, a 302 cubic inch Cleveland (302C). This engine had small ports, smaller valves BUT closed combustion chambers.

The heads with closed combustion chambers raise the compression of the engine about 1 point, and with proper machining of the block, can increase bhp by creating a tight space between the piston & flat surfaces of the head referred to as "squish". As the engine comes from Ford, the space between the piston & head is too great to realize the benefits of "squish".

The subject of cylinder heads is a big one, I've not even scratched the surface. For now let me make a recommendation for you. PI Motorsports sells aluminum cylinder heads manufactured by an Australian company called Cylinder Head Innovations (CHI). Currently they sell a head called the 3V head, but CHI is just introducing a new 2V head. The CHI 2V head, with the new Edelbrock RPM air gap intake manifold, a 750 cfm Holley carburetor, a Competition Cams XE274H camshaft will build you a great street motor, lots of power, excellent throttle response. You can employ your existing exhaust manifolds, and the induction system will be low enough to sit under the engine screen. The intake manifold has the independent runner look of the high rise manifolds. Using the stock exhaust manifolds will prevent this combination from making all the power its capable of, but guessing conservatively, this set up should be good for 75 additional horsepower.

Please be aware that installing new or rebuilt cylinder heads onto a short block with lots of miles on it will most likely result in excessive oil burning.

George