How to Rebuild the Shocks on a Ford Model Aby Douglas Hawk
Many Ford Model As operating today do not have shock absorbers in place, making the ride more uncomfortable. Many other use modernized shocks designed specifically for the Model A. The original shock absorbers were hydraulic double action with glycerin forced from one chamber to another as the lever arm moved. Restoring original shocks is a precise and exacting endeavor.
Remove the four shock absorbers from the frame with the 11/16-inch deep socket. Label each one, identifying its original location. Remove the filler plugs from the ends of the shock absorber link tube attached to the end of the arm (coming off of the shock absorber) with a flathead screwdriver. Drain the fluid into an appropriate receptacle for later disposal.
Remove the shock absorbers’ four covers with a pipe wrench. As you do so, have a rag handy to clean up any mess. Try to save the shaft packing in each shock. This is hard-to-replace material and if it cannot be saved, you will need to make a fresh set for each shock. Carefully tap the two 3/16-inch pins holding the shaft bearing in place with a hammer and pin punch until they are free of the plate. Unscrew the plate with a 1 9/16-inch hex wrench.
Holding the shock absorber in a vise, unscrew the hex nut. Inside the shock you will find the 3/16-inch pins you drove in. Remove these and save them along with the shaft. Clean oil and grease from the shock and use an awl or small chisel to remove any hardened glycerin. Scrape around the ball bearing with a large needle or small pick and then clean the oil ports in the body and rotor, which is the square-surfaced shaft. Clamp the rotor in the vise and loosen the hex nut a couple of turns. The nut keeps in place the packing around the needle valve. Loosen the needle valve. If it is stuck, use a nut loosening substance. Once it is out, the rotor can be machined.
Lock the rotor into a four-way chuck in an engine lathe. Machine the shafts until they are again true, about .009 in diameter. You will need to make a wooden pattern of the threaded plates with the 1 9/16-inch hex wrench and have four or five recast in iron. You will then machine these to match the dimensions of the worn plates and then bore them to match the machined (now smaller) rotors. Place a shallow annular groove in the rotors’ bore. Drill a 3/32-inch connecting hole in the hex to the annular recess. The angle on the outside of the hex hub is 99 degrees and the inner angle is 94 degrees.
Screw the plate into the shock as tightly as you can. Then use a prick punch to mark both the edges of the body and the plate. Take out the plate and drill two holes so that the short pins span the top divider inside the shock’s body. Make sure that the 5/32-inch ball bearing goes in from inside and then drill three holes. The first should go straight through; the second, made with a #20 bit, goes in on the inside. The final hole will hold the locking pin that keeps the 5/32-inch bearing in the #20 hole. According to the original instructions: “The hole is drilled into the edge of the plate. Locate this check from your old plate. Make two rights and two lefts, same as the original. This cannot be done until you locate the locking pin holes. The holes for the locking pins are .002 smaller than the pins measure.”
Reassemble the shocks by using ordinary cotton string to pack around the needle valves. New shaft seals can be made from a 5/16-inch rubberized canvas belt. Punch out 7/8-inch pieces and grind to the correct double-cone shape. Place the ball back into the body before attaching the threaded plate.
Fill each shock with fluid, a combination of 1 ounce of denatured alcohol to every 10 ounces of glycerin for the proper viscosity. Combined, the four shocks will hold 9 1/2 ounces of fluid. Once filled and sealed, allow the shocks to sit inverted for a day or so. Check for any leaks.
Items you will need
- Socket wrench
- 11/16-inch deep socket
- Flathead screwdriver
- Pipe wrench
- 1 9/16-inch hex wrench
- Pin punch
- Tempered awl or small chisel
- Large needle or small pick
- Engine lathe
- Lathe four-way chuck
- Power drill
- 3/32-inch bit
- Prick punch
- 5/32-inch bit
- #20 bit
- 5/16-inch thick rubberized canvas belt
- vintage ford image by charles taylor from Fotolia.com