Let's look at some of the steps involved in the creation of a new cylinder head at Edelbrock. we'll see the CFM figures resulting from extensive flow bench testing and also examine some power production numbers made during cylinder head testing using a 377ci Cleveland test mule on a Super Flow engine dyno.
This photo shows the raw 356T6 aluminum casting for the Cleveland cylinder head displayed next to the new Edelbrock RPM 351C Air Gap intake manifold. Edelbrock engineers are looking for the new cylinder heads and RPM intake to combine and produce a nice 450hp package with lots of potential for growth. | 
After inspection, the raw casting is sent out to the machine shop for the machining process. Here, a completely machined bare casting is shown with the intake side on display. The intake ports are larger than those on the Ford factory 2V heads, yet smaller in diameter than the 4V ports. The runner volume for the Edelbrock Cleveland intake ports comes in at 190 cc. |
The next step is to take the perfect casting and cut it up like a loaf of garlic bread. First, a horizontal cut is made to produce upper-and-lower halves. Next, the cylinder head is cut into slices so the result is an upper-and-lower cross section for every inch of the cylinder head. | 
Each slice of the cylinder head is carefully checked for uniform wall thickness in all areas. Using this procedure, any defects can be spotted, and the needed corrections made in the casting. This is an important aspect of the quality control process, and it also shows the great complexity of the aluminum cylinder head casting. |
The valves planned for the 351 Cleveland head are 2.05 inch for intake and 1.60 inch for exhaust. The one-piece stainless steel valves have 11/32-inch diameter stems and have been undercut and swirl polished for enhanced flow. | 
Manley hardware is used for the top end of the cylinder head, including the guide plates and the 7/16-inch-diameter, screw-in rocker-arm studs. Valveguides are silicon bronze. Positive type valve seals will be seated on top of the guides and used on both intake and exhaust sides. the aluminum spring seats in the head are protected by 1.55-inch-diameter steel cup inserts. |