Intake Manifold Modification

The simplest intake manifold option for a fuel-injection conversion is a modified single-plane carbureted manifold. Shown is a 302 Victor Jr. modified for injectors by Mass Flo EFI. They can do this on a Cleveland manifold as well. We'll be using their system in our own EFI conversion project.
In an EFI system fuel is added directly to each cylinder via individual fuel injectors mounted in the end of each intake manifold runner. Because a fuel injected manifold does not have to provide the signal to the carburetor for proper air-fuel metering, fuel injected manifolds have different design objectives. However it turns out single plane carbureted manifolds and fuel injection manifolds are fairly similar in design; both use individual runners drawing off a common plenum. Thus many guys converting to fuel injection opt to simply modify their carbed single plane intake for injectors and then run a modified "four barrel" throttle body to fit the carburetor flange, or an elbow that allows the use of a late-model Mustang throttle body. The drawback however is the single plane has significantly shorter runner length, which will hurt bottom end torque. While not a concern in a high rpm application, it certainly could put a street car at a disadvantage.

It is for this reason that Tornblom just wanted a true long-runner EFI intake. Most of you are going to look at the route Thomas Tornblom convert his Cleveland to EFI and conclude that it is simply not worth the trouble. However we think it is interesting how Thomas did the legwork in adapting a 351W manifold to a Cleveland block

Shown is a 351C carbureted manifold (this happens to be a Holley Street Dominator.) Note, unlike on a Windsor block, the Cleveland manifold does not have a thermostat housing cast into the front of the intake. The manifold is also a bit narrower due to the Cleveland's shorter deck height.

Trick Flow 351W EFI (lower manifold shown). Note the horizontal manifold bolt holes and thermostat housing. Windsor engines route coolant through the front of the manifold (and rear on some). The manifold is also .300-inch wider than the Cleveland intake.

Adapting a Windsor manifold to a Cleveland block turns out to be less of a nightmare than it sounds like it should be. First is the issue of manifold width. The Cleveland deck height (crank centerline to top of deck) measures 9.206" compared to 9.503" for the 351W ('71-'95). The wider Windsor manifold needs to be flat-milled approximately .150-inch along the sides to fit between the Cleveland heads.

Placing the stock Cleveland intake valley pan on the Windsor manifold shows where the manifold needs to be modified.
On Windsor engines coolant flows through the front of the intake and cast-in thermostat housing. Cleveland manifolds do not have water flowing through the intake and the thermostat is mounted in the block. The Windsor manifold this needed to have the front thermostat housing chopped off and welded up.
Similarly, at the back of the Windsor manifold, the PCV location needs to be cut out to match the contour of the Cleveland's intake valley and also allow clearance for the Cleveland oil pressure sending unit.

The underside of a Cleveland intake manifold. Note the shapes of the end rails and lack of coolant ports at the ends of the intake.

The Windsor manifold will require hacking off the rear PCV and baffle along with the front thermostat housing. The end rails will be reformed.

The rear of the Windsor manifold has been cut and modified. Extra aluminum is TIG welded, shaped to match the Cleveland end rails.

The thermostat housing has been cut off the Trick Flow manifold and a new front rail shaped. The manifold is then milled to ensure a flat sealing surface.

The rear of the manifold now clears the oil pressure sending unit and seals properly to the Cleveland block. Also note the horizontal bolt bosses on the Windsor manifold have been ground down and drilled at the angles necessary to mount to the heads.

The front of the modified TFS 351 Windsor manifold now clears the Cleveland's existing thermostat housing location.

Thomas used the Cleveland's valley pan as a porting template for shaping the Windsor's rectangular ports into the oval shape of the Cleveland head.

The final steps of converting the TFS Windsor intake for use on a Cleveland are to address the ports and bolt holes. Both engines use twelve manifold to head mounting bolts, and the center four on both the Windsor and Cleveland manifold are horizontally oriented. However the remaining ten are angled, and the angle is not the same between the two engine types. Thomas solves this by grounding down the bolt hole casting bosses and then re-drilling (See image 9.)

The final step is to port match the Windor's rectangular ports to the oval ones on the Cleveland head. Thomas used the intake valley pan as a guide. The TFS 351W lower has plenty of material to enable the ports to be opened up to the larger Cleveland shape.


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