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How to Replace a Timing Chain for a 302

by John Stevens J.D.; Updated November 07, 2017

Items you will need

  • Wrench

  • Vibration dampener puller kit

  • Screwdriver

  • Timing chain cover gasket

  • Water pump gasket

  • Gasket sealer

  • Antifreeze

  • Water

Unlike most modern engines, the 302 was never equipped with overhead camshafts. The camshaft was instead inserted through the center of the block and a timing chain was used. The purpose of a timing chain is to connect the engine’s crankshaft to its camshaft, and to ensure that both components spin in a precise sequence. Over time, the chain stretches, making it difficult to set the ignition timing. Fortunately, because the 302’s distributor does not have to be removed, replacing the timing chain on a 302 is easier than on many other types of engines.

Drain the antifreeze from the radiator by removing the petcock plug at the base of the radiator with a wrench. Tighten the plug into the radiator once the radiator has finished draining.

Remove the vibration dampener from the crankshaft. Remove the single bolt located in the center of the dampener, then bolt a vibration dampener puller to the dampener with the bolts supplied with the puller kit. Rotate the threaded rod in the center of the puller in a clockwise direction with a wrench until the dampener detaches from the crankshaft.

Disconnect the bottom radiator hose, the heater hose and the intake manifold hose from the water pump. Each hose connects to the water pump with a band clamp secured with a screw. Twist each screw in a counterclockwise direction with a screwdriver, then pull the three hoses off of the water pump.

Remove the water pump and the timing chain cover. Remove the bolts that secure the water pump to the timing chain cover with a wrench, then pull the water pump off of the cover. The timing chain cover is also held in place with several retaining bolts. Note that four of the cover’s bolts enter the bottom of the cover through the front of the oil pan. Remove each bolt and pull the cover off of the engine to expose the timing chain.

Turn the crankshaft until the two marks on the timing chain’s gears align. Removing the timing chain with the gears in alignment will avoid having to set the engine’s ignition timing later. A small circle has been stamped into one edge of each timing chain gear. The marks are in alignment when the mark on the larger gear is in the six o’clock position and the mark on the smaller gear is in the twelve o’clock position. Insert the bolt used to secure the vibration dampener to the crankshaft into the tip of the crankshaft, then turn the bolt in a clockwise direction to rotate the gears.

Remove the oil thrower ring from the crankshaft and the fuel pump eccentric from the camshaft. Surrounding the tip of the crankshaft is a thin metal disk, called an oil thrower ring. Slide the ring off of the crankshaft. Bolted to the center of the camshaft’s timing chain gear, which is the larger of the timing chain’s two gears, is a circular metal piece approximately two inches in diameter. This piece is called a fuel pump eccentric, and is used to operate the fuel pump. Remove the single bolt located in the center of the eccentric, then pull the eccentric off of the timing chain gear.

Remove the timing chain. The bolt used to secure the fuel pump eccentric to the upper timing chain gear also held the upper timing chain gear to the camshaft. Since the eccentric has already been removed, simply pull the upper timing chain gear off of the camshaft. With the upper timing chain gear removed, the chain will go slack. Pull the lower timing chain gear off of the crankshaft.

Install the new timing chain. Separate the replacement timing chain from its upper and lower sprockets. Slide the lower timing chain gear onto the tip of the crankshaft. Note that the tip of the crankshaft features a raised metal piece that extends down the length of the crankshaft. This metal piece is designed to slide through a small cutout within the lower timing chain gear. Position the lower timing chain gear onto the tip of the crankshaft, then rotate the gear until its slot slides over the raised metal piece on the crankshaft. Wrap the timing chain around the lower gear, then onto the upper gear. Make sure that the small circle on the upper timing chain gear is at the six o’clock position. Position the upper timing chain gear onto the tip of the camshaft, then install the fuel pump eccentric with its bolt into the center of the upper timing chain gear to secure the timing chain assembly in place. Slide the oil thrower ring onto the tip of the crankshaft.

Install the timing chain cover and the water pump. The timing chain cover must be installed first, as the water pump bolts to the front of the timing chain cover. Install both components with new gaskets coated with gasket sealer.

Connect the radiator hose, the intake manifold hose and heater hose to the water pump. Slip each hose onto its respective fitting on the water pump, then tighten the three hose clamps with a screwdriver.

Install the vibration dampener onto tip of the crankshaft. The dampener is installed similarly to the lower timing chain gear. Like the lower timing chain gear, the dampener also features a slot that slides over the metal pin on the tip of the crankshaft. Twist the dampener until it aligns with the pin, then install the dampener’s retaining bolt with a wrench.

Fill the radiator with a 50/50 mixture of new antifreeze and water.

References

About the Author

John Stevens has been a writer for various websites since 2008. He holds an Associate of Science in administration of justice from Riverside Community College, a Bachelor of Arts in criminal justice from California State University, San Bernardino, and a Juris Doctor from Whittier Law School. Stevens is a lawyer and licensed real-estate broker.

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