Download Ford RPM Air-Gap 302 Manifold For Small Block Ford Engines Service Manual – MANIFOLD AND CARBURETOR HEIGHT: 1. Remove the air cleaner. HEIGHT B 2. Lay a straightedge (such as a yardstick) across top of carburetor from front to back. 3. Measure from block and manifold end seal surface. See Figure 3. 4. Record measurements HEIGHT A in blank spaces labeled OM1 and OM2. 5. Measure height of Fig. 3 carburetor and record in space C3. NOTE: Most 4-bbl carburetors are about 3-1/4″ tall (mounting flange to air cleaner flange). 6. Place straightedge on top of new manifold including any adapters or gaskets you plan to use. 7. Measure distance from end seal surface as you did on stock manifold. See Figure 4. 8. Record measurements in spaces NM1 and NM2. 9. Add carburetor measurement C3 to new manifold figures you recorded. 10. If the new combination is taller, subtract this amount from the hood clearance figure for the new hood clearance. CAUTION: You must maintain at least 1/2″ clearance between the hood and air cleaner because of engine torque. If you have insufficient clearance, a low profile air cleaner may solve the problem. NOTE: On engines without end seal surfaces, select a standard point from which to measure.