In the middle of development,...
In the middle of development, this 351 Cleveland combustion chamber was cut in order to make the cut.
There's been a lot of talk lately about a brand-new Edelbrock cylinder head for the Ford 351 Cleveland engine. The rumors are true, and recently a preproduction prototype of this head was made available exclusively to Mustang & Fords at Edelbrock corporate headquarters in Torrance, California. Let us give you the first ever look at their new 351 Cleveland cylinder head (PN 61629). This is the first cylinder head that Edelbrock has made for the Ford 335-Series Cleveland V-8, which was produced from 1970 until 1974. The Cleveland shared no interchangeable parts with the Ford 351 Windsor V-8, which was introduced in 1969. The Cleveland found its way into many Mustangs, as well as other Ford vehicles during that four-year period. The Ford Cleveland V-8 featured a distinctive splayed or canted valve arrangement, which provided better engine breathing characteristics when compared to a conventional in-line valve configuration. Ford offered both 2V and 4V heads for the 351C; the smaller 2V heads worked well for street applications. The larger 4V Cleveland cylinder heads had cavernous intake ports that flowed big time at the upper rpm ranges, but left the engine stumbling around town. what has been needed is a single cylinder head that offers the best characteristics from both of the original Ford versions.
The genesis of a modern cylinder...
The genesis of a modern cylinder head begins with the computer. Here an Edelbrock design engineer has a diagram of the new Ford 351 Cleveland cylinder head up for viewing. The image can be modified and manipulated so that it can be viewed from any angle on the screen.
Edelbrock has decades of experience designing aluminum cylinder heads, and they offer perhaps the widest variety available in the aftermarket. Edelbrock Design Engineer Ulises Gonzales headed up research and development for the new Cleveland cylinder head project. As well as being head honcho for the Cleveland project, he was our host as we traveled straight into the heart of the Edelbrock design facility. The new Cleveland cylinder head is intended to offer the best of both worlds--excellent performance in both street and racing applications. All design parameters are carefully balanced in the new head, and the intake port size lies between the factory 2V and 4V heads. According to Ulises, the new 351C heads have a flow potential well beyond the Victor Jr. cylinder heads made for the 351W.
As the design of the cylinder head proceeds, a flow block containing intake and exhaust passages for one cylinder is created. Modifications to the port design can be created in the flow block by adding or subtracting material. Changes can then be tested directly on the flow bench. Results for the new 351C heads are:
| Flow Bench Results | | LIFT | INTAKE CFM | EXHAUST CFM |
|---|
| .100 | 70.2 | 48.7 |
| .200 | 139.1 | 92.9 |
| .300 | 204.8 | 123.0 |
| .400 | 242.5 | 145.4 |
| .500 | 267.9 | 160.8 |
| .600 | 271.6 | 170.5 |
|
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...
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...
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...
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...
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...
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...
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.
For the valvetrain, a single...
For the valvetrain, a single valvespring with a damper was chosen. The 1.54-inch-diameter springs have a 1.90-inch installed height. They have 125 pounds of pressure at the seat, and are held in place by chrome moly retainers with heat-treated single slot keepers.
This top view of the assembled...
This top view of the assembled 351 Cleveland head clearly shows the splayed valve arrangement. The valves are neither in line nor are they perpendicular to the engine centerline. They're arranged for maximum flow potential in a hemispherical configuration. Completely dressed, the cylinder head weight is 32 pounds.
This interesting comparison...
This interesting comparison shot of the finished cylinder head and the bare casting shows just how much work has to go into the raw piece in order to create a working cylinder head. With the exhaust face showing, the generously sized ports can be seen. The slightly squared-off exhaust ports have the stock bolt pattern and are in the original location. The exhaust runner volume is 95 cc.
The combustion chamber volume...
The combustion chamber volume here is a relatively small 60 cc, and when combined with the large 2.05-inch intake valves, there's not a lot of room left over. The valve seats are made of hardened ductile iron for use with unleaded fuel.
The question soon arose about...
The question soon arose about what awaits the person who wants to try these Cleveland heads on a Windsor block. This photo shows how the castings are prepared for this possibility. The large cooling passage on the combustion face (shown on the left) will be threaded in the production head, and plugs will be furnished. The small dimple seen on the intake face of the cylinder head denotes the spot where drilling should be done to open up the water passageway for use on the Windsor engine. With the threaded plug in place and the other passageway opened up, the quest for an intake manifold can begin. We've even heard rumblings at Edelbrock that production of a Clevor-type intake might be in the cards for the near future.
The numbers for this graph...
The numbers for this graph were obtained with a 377ci Cleveland Ford engine. It was bored 0.040-inch over and equipped with a 3.700-inch stroke crankshaft. A connecting rod with a 6.00-inch center-to-center length was used. The compression ratio on the engine was 9.7:1 and a 750-cfm carburetor was installed on top of an Edelbrock RPM 351C Air Gap intake. The camshaft used had a duration at .050 of 234 degrees intake and 244 degrees exhaust. Lobe lift for the cam on intake was .325 and .340 on exhaust. Lift at the valve worked out to .562 intake and .588 exhaust, and lobe separation was 112 degrees.
| Edelbrock Cylinder Head Dyno Results | | RPM | HP | TORQUE |
|---|
| 2,500 | 174.9 | 367.3 |
| 3,000 | 224.5 | 383.1 |
| 3,500 | 255.7 | 393.8 |
| 4,000 | 335.4 | 440.3 |
| 4,500 | 381.7 | 445.4 |
| 5,000 | 414.7 | 435.6 |
| 5,500 | 441.5 | 421.6 |
| 6,000 | 456.2 | 399.3 |
| 6,500 | 454.8 | 367.5 |
|
The goal to create a 450-plus-horsepower package for the Cleveland Ford has clearly succeeded, and this figure will no doubt be surpassed as larger power-making components are added to the equation. The Edelbrock aluminum cylinder head for the Ford 351 Cleveland engine should be available at a competitive retail price (to be announced) by the time you read this.