How to Change a 390 Ford Distributor

The distributor on a Ford 390 cubic-inch engine is mounted on the intake in the front of the engine. Replacing the distributor is an exacting procedure. It controls the spark timing for the ignition and if installed even a few degrees off, will result in a rough engine at best. It is the type of procedure where attention to detail is important. Most of the Ford 390 engines are in early-model vehicles with point-type distributors.

Things You'll Need

• Common screwdriver
• Set of wrenches
• Ratchet
• Set of sockets
• Marker of some sort, white preferably

Instructions

1. Mark all the spark plug wires so they can be replaced into their original position. Pull them out of the cap. Remove the distributor cap using the screwdriver.

2. Place a socket and ratchet on the large crankshaft bolt and turn the engine clockwise, slowly, until the line on the harmonic balancer is on the 0 mark on the timing plate. The timing plate is on the timing chain cover. It is graduated in degrees before top dead center (BTDC) and after top dead center (ATDC). In the center of these graduations is a V-shaped cut with a 0.

3. Mark the position of the metal end of the rotor where the cap meets the distributor. This is important to install the distributor correctly. Pull the vacuum advance hose off the distributor. Mark the base of the distributor where it enters the manifold. Disconnect the electrical wire (power wire) from the distributor.

4. Remove the distributor hold down bolt using a wrench. Lift the hold down bracket up to remove it. Twist the distributor a little as it is lifted out of the manifold.

5. Lay the new distributor next to the old one, if a new one is being installed. Mark the new distributor in the exact same locations. Install a new gasket on the distributor. Prepare to install it by holding it in the same direction as it was removed. Point the rotor toward the mark.

6. Insert the distributor into the intake manifold. In order to get the rotor to face in the exact same direction and over the mark made previously, it will need to be turned about 15 degrees counterclockwise first. When the distributor is inserted, the bottom distributor gear meshes with the camshaft gear, which moves the rotor clockwise about 15 degrees. Once the distributor is in and the rotor is facing in the correct direction, turn the distributor housing until the bottom mark lines up with the mark on the block made previously.

7. Install the distributor hold down clamp and tighten the bolt. Connect the vacuum line to the vacuum advance. Connect the electrical wire to the distributor. Install the distributor cap and tighten with the screwdriver. Install the spark plug wires.