Another comparison shot between...
Another comparison shot between an R07 (left) and an SB2.2. It is difficult to see with the eye, but the valves on the R07 have been moved closer to their relative side of the head (intake valves closer to the manifold and exhaust valves closer to the headers). The result is less angle on the pushrods between the lifter and rocker arms, which allows wider ports. It also makes the ports shorter, but MBE owner Matt Bieneman says that for engine packages working in lower rpm ranges, the extra length can be made up in the intake runners.
The new heads remove this situation by rearranging the valve order. Now, it is I, E, I, E, I, E, I, E, and each exhaust valve is surrounded by an intake to help cool it. The new valve arrangement will, however, require a different lobe arrangement on the cams. Of course, it is already a given that the SB2.2 and other Chevy small-block cams will not interchange with the R07 because of the wider bore spacing.
In addition, removing the hot spot between the exhaust valves will help equalize the coolant temperature within the block, which will reduce localized movement of the material. This means better ring sealing and possibly even better sealing at the head gasket. The cool air flowing through the nearby intake ports will also help make the environment a little friendlier for the exhaust valves and seats.
In addition to the new valve arrangement, there has also been a significant change made to the ports. Almost all small-blocks from any manufacturer use a port angle of at least 10 degrees. This angle sends the air/fuel mixture through the port and into the combustion chamber on an angle so that it creates a vortex, or swirl, inside the chamber. This swirl helps keep the fuel suspended in the air so that it burns as efficiently as possible when the spark plug fires.
This new port, however, is very straight and very short. Veteran cylinder head porter Dennis Warner calls this a "low-swirl port" but believes the overall improvements in flow should outweigh the disadvantage that comes with less swirl. One trick he feels might work to increase swirl is to "twist" the port so that the walls, while still parallel, are no longer vertical. This will help produce more tumble and swirl before the air/fuel charge enters the combustion chamber.
This hole is an oil gallery...
This hole is an oil gallery that will feed oil from the block to integrated valvespring oilers in the valve covers. Notice that it is also grooved to accept an O-ring.
As this feature went to press, Bieneman and Warner said that they had little information on how well the ports will actually flow because NASCAR had yet to release the templates they must work within, and actual castings are still so scarce that they cannot afford to experiment until they know the exact rules package.
Along with the straighter ports, the valve locations have also been moved closer to the side of the head. The result is that the valves are more staggered than before. This should help the rockers be more centered over the appropriate cam lobe and straighten the pushrods. Bieneman says that this change will allow the wider ports to deliver even better flow numbers.
Since the intake ports are so straight, both Bieneman and Warner believe that the intake manifold design that will work best with these heads will have a very large plenum that is extended toward both the front and back of the engine. This large plenum will help move the outside intake runners closer to the ports so that they won't have to curve as much to make the port entrance. This design will also shorten the outside runner length to help it match the length of the interior intake runners.
Of course, this short-runner/big-plenum design lends itself well to Cup racing, where the rpm is high and the power range is narrow. In a short-track car-say a dirt Late Model-the plenum can easily be decreased or even raised to increase the runner length and move the powerband lower in the rpm range. Another difficulty with a large-plenum manifold is that it reduces the signal at the carburetor. Warner says that this can be overcome, but it requires a crafty carburetor tuner.
This manifold is for an SB2.2,...
This manifold is for an SB2.2, but the design is a good example of what Bieneman and Warner feel will work well with the R07. The elongated plenum makes the outside runners appear shorter to the engine, balancing the runner length between the inside and outside pairs. It also has the advantage of straightening the flow path of the air/fuel charge.
The raised outer rail on the...
The raised outer rail on the head is almost certainly designed to catch oil and hold it against the springs when the valve covers are flooded. We've placed a spring on one of the spring pads for reference. Also, notice the strategic placement of the oil drain hole between the spring and the exhaust spring pad in the foreground.
Below each of the intake ports...
Below each of the intake ports is an inlet to bring water from the valley cover to the cylinder head's water jacket. Each inlet points water directly to the outside of its corresponding combustion chamber.