How to Set the Timing on General Carsby Contributing Writer; Updated June 12, 2017
The term "Shovelhead" refers to a Harley-Davidson Big-Twin engine that was produced from circa 1966 to 1984. The first generation Shovelhead from 1966 through 1969 was actually the same engine as the Panhead engine that it replaced, except for the updated cylinder heads. All Shovelheads came from the factory with a standard breaker points ignition until the 1978 model year. While the later capacitive-discharge electronic ignition systems produce more top-end horsepower, the original points system is simple and reliable. One of its advantages is that even a neophyte can easily set the timing statically while the engine is not running.
Under The Hood:
- How to Set the Timing on a Caterpillar C15
- How to Set the Timing on a 350 Engine
- How to Set the Timing on an AMC 304
- How to Set the Timing on Shovelhead Points
- How to Set the Timing on Wisconsin Engines
- How to Set Timing on a 4 Stroke 1 Cylinder Engine
- How to Set the Timing With a Dwell Meter
- How to Set the Timing on a Carburetor
Park the piece of heavy equipment, industrial vehicle or boat in a ventilated area that has a nearby 110-volt electrical outlet. Remove the engine cover.
Connect the power cord from the Cat-ET unit to the outlet. Select the “On” function on the unit and insert the software disc. Allow the disc to load as indicated on the display.
Refer to the service manual for the equipment, vehicle or boat and locate the ECM box. Pull off the C15's connector at the box. Move the connector and wires to one side.
Attach the ECM interface adapter to the ECM box. Connect the main interface lead from the Cat-ET unit to the adapter. Start the C15 engine and allow it to idle.
Select the “Electronic Unit Injection” function on the Cat-ET unit. Wait until the display shows a range of timing parameters and a “Download in Progress” window.
Select the “Program” function on the Cat-ET unit. A progress bar in the window indicates the injector timing is under way. Allow the programming to complete, as indicated by the progress bar.
Turn off the C15 engine. Disconnect the adapter and Cat-ET lead from the ECM box. Reattach the C15 ECM connector to the box.
Items you will need
Cat-ET and software disc
ECM interface adapter
Connecting a Timing Light to a 350 Engine
Disconnect the vacuum hose from the distributor, and plug the line with a bolt.
Connect the positive lead (red) on the timing light to the positive battery terminal on your vehicle. Connect the negative lead (black) on the timing light to the negative battery terminal.
The third wire on the timing light and its clip fits between the No. 1 spark plug and wire. The No. 1 spark plug is the first one on the right as you are facing the engine from the front of the vehicle. Pull the wire off the No. 1 spark plug, and insert the clip from the timing light between the No. 1 spark plug and wire.
Make sure all the electrical leads for the timing light are routed away from any moving parts on the engine and any parts that become excessively hot.
Locate the timing tag on the front of the engine. It will be bolted to the lower end of the timing chain cover. Clean the timing tag using an automotive solvent.
Locate the groove across the crankshaft pulley. You may wish to "bump" the starter to rotate the groove to the top of the pulley. Do this by inserting the key into the ignition and turning the key to start. Quickly turn the key back to the "off" position before the engine can start. Continue until the groove is on top of the pulley.
Use white paint or chalk to highlight the groove on the crankshaft pulley. Also mark the value on the timing tab that represents the correct ignition timing value as specified on the tuneup decal in the engine bay.
Setting the Timing on a 350 Engine
Turn on the engine and allow it to warm up to normal operating temperature. Remember to keep the electrical leads from the timing light clear of the engine.
Point the timing light toward the timing tab and crankshaft pulley. The light will make the timing marks appear stationary.
If the two marks line up, the timing is set correctly. If not, you must adjust the timing.
Adjusting the Timing on a 350 Engine
Shut the engine off.
Slightly loosen the locknut on the distributor clamp at the base of the distributor. You only need to loosen the locknut enough to be able to rotate the distributor.
Turn the engine on.
Aim the timing light toward the timing tab and crankshaft pulley. If the two marks are out of alignment, slowly rotate the distributor until the marks line up.
Shut off the engine.
Tighten the locknut on the distributor clamp at the base of the distributor.
Turn on the engine. Use the timing light to make sure the mark on the timing tab and the groove on the crankshaft pulley are still in alignment.
Turn off the engine. Unplug and then reconnect the vacuum line to the distributor.
Disconnect the timing light from the engine and battery.
Items you will need
Automotive cleaning solvent
Chalk or white paint
GM ignition wrench
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.
Items you will need
Brake parts cleaner
Golf tee or nail
Remove the spark plugs, the timing port plug (on the left side of the engine case between the cylinders) and the timing cover (on the right side of the engine case).
Place your thumb over the front-cylinder spark plug hole and kick the engine over slowly with the kick starter. Stop when you feel pressure on your thumb. This indicates that the front piston is approaching TDC (top dead center) of the compression stroke.
Look in the timing port and continue to slowly kick over the engine until the advance mark (vertical line) is centered in the port.
Connect the red lead of the test lamp to the negative coil terminal, and the black lead to a good ground. Turn on the ignition switch.
Sit on the ground facing the timing mechanism. Loosen the timing plate screws.
Reach into the timing mechanism and grasp the point cam, which is in the center of the mechanism. Twist the point cam counterclockwise until it stops. Hold it in that position while you move the points plate (the round plate that the points are mounted on) counterclockwise until the test lamp lights.
Turn the points plate slowly clockwise while holding the points cam counterclockwise. Stop as soon as the test lamp goes out. Tighten the timing plate screws to lock the adjustment.
Turn off the ignition switch. Replace the timing cover, timing port plug and spark plugs.
Items you will need
Timing test lamp
Spark plug wrench
3/8 inch hex wrench
Open the breaker box, which is usually located on the left side of the engine.
Inspect the point gap. Fairly accurate timing can be achieved by simply setting the breaker point gap to its specified distance. Consult the engine's documentation for the exact measurement to use. The Wisconsin TRA-10D and TR-10D, for example, require a breaker point gap of 0.02 inches. Setting the gap accurately requires a feeler gauge of the appropriate size, which is placed between the two points while a screwdriver is used to move the plates via the adjusting slot. Although this will provide reasonably accurate timing, a timing light will be more accurate.
Disconnect the coil primary wire, located at the bottom of the breaker box.
Inspect the flywheel shroud. The opening on the right side reveals the timing mark on the flywheel.
Turn the starter sheave clockwise and watch the breaker arm movement. Stop when the engine is on the compression stroke. It is now OK to line up the flywheel timing mark with the pointer.
Connect the timing light to the terminal stud, in the lower part of the breaker box. Connect the other wire to ground.
Loosen the lock screw on the contact support plate. Only loosen it enough to allow the plate to move -- no further.
Close the points in the adjusting slot using a screwdriver. This will turn the timing light on. When it switches on, turn the screw the opposite way slowly. As soon as the light goes out, stop and keep the points in this state.
Tighten the lock screw.
Test the timing. Turn the flywheel counterclockwise, which will switch on the timing light. Then slowly turn the flywheel clockwise. The light should switch off at the same time as the flywheel timing mark lines up with the pointer. If this is the case, the engine is timed correctly.
Disconnect the timing light from the terminal stud.
Reconnect the coil primary wire to its connection in the lower part of the breaker box.
Remount the cover on the breaker box.
Items you will need
Correct Flywheel Timing
Place the engine on a solid surface where it will not slide. Use a socket and wrench to remove the main engine cowl. The cowl usually has three bolts that secure it, and it sits on the side or top of the engine. Pull off the cowl. Inspect the crankshaft for a ratchet device connecting to the pull start, or a socket that holds the flywheel in place.
Use a hammer to tap the ratchet device counterclockwise to unscrew it. Use a socket to remove the flywheel nut, if it has this fastener. Do not remove the flywheel yet. Use a socket to remove the spark plug from the engine. Turn the flywheel by hand while you hold your finger over the spark plug hole. Stop when you feel air pressure on your finger.
Inspect the flywheel and magneto. The magneto looks like a coil with two prongs extending to the edge of the flywheel. The flywheel has a magnetic pickup on its edge that should align with the end of the magneto prongs. If it does not align, the timing has slipped. To confirm it, rotate the flywheel back and forth rapidly. If it moves on the crankshaft, the flywheel has sheared the key or slipped on the shaft.
Place a flywheel puller over the flywheel, and hook the puller prongs on the back of the flywheel. Place the puller shaft in the recessed end of the crankshaft, and turn the puller handle clockwise until the flywheel comes off. Inspect the crankshaft key-way for damage, and remove the damaged key. Place a new key in the crankshaft key-way slot. Tap the key with a hammer to set it firmly.
Improve Ignition Timing
Use a screwdriver to unscrew the silver, circular case that holds the points and condenser. Loosen the one adjusting screw on the points. Remove the other screw with a screwdriver. Remove the two small spring clip wires from the points. Use a screwdriver to remove the single screw that holds the condenser in place. Discard the the old points and condenser. Slip the new points in under the adjusting screw, and insert the other points screw. Tighten both screws with light pressure only.
Place a new condenser into position, and tighten the single screw with a screwdriver. Attach both small wires in the spring clip. Use pliers to turn the crankshaft until the small cam lobe on the crankshaft rests against the rubbing block connected to the points. Refer to your owner's manual for the correct gap measurement required for your points setting. For example, it might be .020. Select the correct blade and place it between the contact pads on the points.
Place a screwdriver in the points adjustment slot and turn it back and forth to close or open the points. Once you have the points pads closed on the proper blade thickness, tighten the points adjusting screw and then the mounting screw. Replace the points cap and tighten the cap screws with a screwdriver. Set the flywheel over the crankshaft and push it down over the key-way as far as possible. Screw the ratchet device back down, or the flywheel nut and tighten it with a hammer or socket.
Insert the spark plug and screw it in with a socket. Reconnect the spark plug wire. Place the engine cowl back on the engine and insert the bolts. Tighten the bolts with a socket. Pull the rope starter to test the engine.
Items you will need
Engine repair manual
Place the vehicle transmission in "Park" for an automatic and "Neutral" for a manual version. Apply the emergency brake and raise the hood. Do not work on a hot engine -- let it cool somewhat before making the adjustment. Look at your distributor cap and determine if it has an adjusting window on the side of the cap. If it does, you will set the points with an Allen wrench. If not, remove the distributor cap by turning the two cap hold-down springs outward with a slot screwdriver, or unscrew the cap with a Phillips screwdriver.
Hook up the red lead to a dwell meter on the negative (-) terminal on the ignition coil or coil pack. Refer to your owner's service manual if you are unsure of the coil or coil pack location and terminal position. Hook up the other meter lead to a good engine ground source. For the adjustable window distributor, set the meter for the degree or "Dwell" scale. Place an Allen wrench through the adjustment window on the distributor cap, connecting it to the adjustment screw.
Instruct an assistant to start the engine. Read the dwell in degrees on the dwell meter screen. Refer to your owner's manual for the correct dwell angle setting (i.e. 30 or 32 degrees). Turn the adjustment screw in (clockwise) to increase the dwell, or out (counterclockwise) to decrease the dwell. Once the needle reads the correct number, withdraw the Allen wrench and shut the engine off.
Wedge the distributor cap away from the distributor body, with the bottom facing up. This procedure works for the non-window distributor cap. Remove the rotor with a screwdriver, or by hand. Loosen the two screws that hold the points in place on the distributor plate. Loosen them only enough so the adjustment arm on the points move. Place a slot screwdriver in the adjustment slot on the points and have your assistant turn the engine over. Read the needle on the dwell meter. Turn the screwdriver clockwise to increase the dwell, or counterclockwise to decrease the dwell.
Instruct your assistant to turn the key off. Tighten the ignition point plate screws. Replace the rotor by hand, or use a screwdriver to tighten in place. Set the distributor cap back onto the distributor and use the appropriate screwdriver to refasten the screws or the small hold-down clamps. Refer to your owner's manual for the proper ignition timing of your engine. For example, it could be 8 or 10 degrees BTD (before top dead center)
Disconnect the vacuum line that attaches to the distributor vacuum advance diaphragm on the side of the distributor. Locate the notch on the crankshaft pulley and the small metal timing tab on the front of the engine block. Use a rag to wipe the small lines and numbers clean on the tab and pulley. Use a socket, extension and ratchet wrench to loosen the distributor hold-down bolt, but only enough so you can move the distributor with mild pressure.
Hook up the red lead of a timing light to the positive terminal on the battery. Hook up the negative lead of the timing light to the negative battery terminal. Place the timing light wire clip on the number 1 spark plug wire (check your repair manual for its location). Have your assistant start the engine. Point the timing light nozzle down at the metal timing tab. Turn the distributor so that the notch in the crankshaft pulley aligns with your correct degree number on the tab, according to your service manual.
Shut the engine off. Tighten the distributor hold-down bolt with the socket, extension and ratchet wrench. Reconnect the vacuum advance line to the distributor. Unhook the timing light leads. You have now set the timing after you have adjusted the points for the proper dwell angle.
Items you will need
Owner's service manual
Socket extension (8 to 12 inches)
Turn over the engine. Wait for the engine to warm up to its normal operating temperature, either by letting the engine idle or using the device for a few tasks in the interim — depending on what device the engine is powering.
Turn off the engine.
Locate the side of your carburetor with one or more screws sticking out. If the carburetor has only one screw, that is the idle speed and mixture adjuster. If it has more than one screw, then each screw will govern the mixture under different engine loads. While carburetors with two screws will frequently have the idle adjustment screw be on the left and the high speed adjustment screw be on the right, this is not a firm rule. Consult your carburetor's manual to determine exactly what each screw governs.
Turn the screw whose governing function you wish to adjust clockwise to reduce the fuel in the air-fuel mix being fed into the engine, and turn the screw counterclockwise to increase the fuel in the mixture. Turn over the engine after making your adjustments to see the results of your adjustments on the engine.
Repeat the cycle of turning off the engine, adjusting the appropriate function on the carburetor, and turning back on the engine to check the results until you are satisfied with the results.
Items you will need