How to Set the Timing on an AMC 304by Dan Ferrell
During the 1970's, the American Motors Corporation fitted some of its vehicle with the 304 V8 engine. As part of the tuneup procedure, you can adjust the timing on the 304 to synchronize the spark produced by the ignition coil with the pistons during their four-stroke cycle. This is necessary to prevent spark knock, preserve fuel economy and engine performance. You can set the timing on your AMC 304 at home in a few minutes with a minimum of tools.
Start your engine and let it warm up for about 20 minutes.
Turn off the engine, open the hood and clean the timing scale located above the crankshaft pulley. This is the pulley on the front and bottom of the engine, which runs the drive belts. Also, clean the notch located on the crankshaft pulley itself. Use brake parts cleaner and lint-free towels to wipe dirt and grease from these areas, if necessary.
Apply a light coat of correction fluid to the numbers and lines on the timing scale and the notch on the crankshaft pulley to make them easier to read during timing adjustment.
Get your timing light and connect the tool's red clip to the positive (red cable) battery terminal and the tool's black clip to the negative (black cable) battery terminal. Hook the timing light clamp-on clip to the number one spark plug wire on the engine. If you stand if front of the engine, facing the drive belts, the number one plug wire will be the first one on your right side. Make sure the clamp-on clip is as close to the spark plug as possible. Route all the timing light wires away from drive belts, cooling fan and other moving parts in your vehicle.
Pull off the thin vacuum hose from the distributor by hand and plug the hose with a golf tee or nail. The distributor is the component where the all the spark plug wires connect to.
Look for the underhood sticker around the engine compartment, which contains tuneup specifications. This might be on the radiator bracket or to either side of the engine compartment by the strut pillars or on the firewall. The sticker should tell you the idle speed the engine should be adjusted to during the timing procedure and the correct timing setting for your car. Otherwise, consult your vehicle service manual. In most cases, the idle speed should be set to 500 rpm.
Adjust the idle speed by turning the screw next to the carburetor using a standard screwdriver. This screw serves as a stop for the lever that moves the throttle plate in the carburetor. If an assistant slowly depresses the accelerator pedal, you will see the lever moving to open the throttle plates. Start the engine and let it idle. Turn the adjusting screw as your assistant watches the tachometer. When the needle on the tachometer is at 500 rpm, or the number specified on the underhood sticker, stop turning the adjusting screw.
Grab your timing light and, with the engine idling, aim it at the timing scale above the crankshaft pulley. Make sure the notch on the crankshaft pulley points to the correct degree number on the timing scale as indicated by the sticker on your vehicle.
Loosen the mounting bolt at the base of the distributor using a distributor wrench, if you need to adjust the timing.
Ask your assistant to slowly turn the distributor left of right until the notch on the crankshaft pulley aligns with the correct mark on the timing scale. Tighten the mounting bolt on the distributor with the wrench and double check the notch on the pulley is still pointing to the correct mark on the timing scale.
Turn off the engine, replace the vacuum line to the distributor and disconnect your timing light.
- "1979 AMC Technical Service Manual"; American Motors Corporation, Service Dept.; 1978
- "Modern Automotive Technology"; James E. Duffy; 2003
Things You'll Need
- Brake parts cleaner
- Lint-free towels
- Correction fluid
- Timing light
- Golf tee or nail
- Standard screwdriver
Since 2003 Dan Ferrell has contributed general and consumer-oriented news to television and the Web. His work has appeared in Texas, New Mexico and Miami and on various websites. Ferrell is a certified automation and control technician from the Advanced Technology Center in El Paso, Texas.