Broken bolts are not uncommon when working on older engines like the Ford 390. Exhaust manifold bolts are rated for strength, but heat generated at the exhaust manifold welds the threads over time, leaving you with a broken-off bolt head in your socket. In most cases, attempting to remove the bolt stem with locking pliers does little more than expand the blood veins in your forehead. If your Ford truck has been used in the rain or snow, you may encounter more than one broken bolt when removing the exhaust manifold on a Ford 390 truck engine. Removing a broken bolt is challenging, but it can be done.
Instructions
Tap-Out
1. Flatten the broken end of the bolt with an electric grinder or a flat file. Skip this step if the bolt is broken off inside the head.
2. Dent the end of the bolt in its center using a center punch and hammer. The dent ensures that the drill bit remains in the center of the bolt.
3. Chuck a 3/16-inch left-hand drill bit in an electric drill. Set the drill to reverse. Measure the diameter of another exhaust manifold bolt and drill the 3/16-inch hole to this depth in the center of the broken bolt.
4. Insert the point of a 1/4-inch-diameter extractor tap into the drilled hole. Thread the tap counterclockwise into the hole using an open-end wrench on the outer end of the tap. Continue turning the tap counterclockwise with the wrench to extract the broken bolt.
Retrofit Bolt Head
5. Select a hex-head nut that is compatible with one of the exhaust manifold bolt threads. Attempt to thread the nut onto the end of the broken bolt. Do not cross-thread the nut. If the nut will not thread, tap it lightly with the hammer so it stays in position similar to a bolt head.
6. Wear your welding gloves and hood. Weld the nut to the end of the broken bolt using a wire welder. Build a pool of weld in the center of the nut, taking care not to get weld on the flat sides of the nut. Allow the weld to cool completely.
7. Set up a breaker bar with the appropriate size socket for the hex-head nut. Push the socket onto the nut and extract the broken bolt by turning counterclockwise.
