PATH: Engine Mechanical Engine Mechanical Components Valve Lash (Clearance) Adjustment

PATH: Engine Mechanical > Engine Mechanical Components > Valve Lash (Clearance) Adjustment > 8-260, 289, & 302 Engines

8-260, 289, & 302 Engines

Position of the crankshaft for valve adjustment— 260 and 289 engines Click to Enlarge

This procedure for the 289 and early 302 V8 engines is designed for engines in which the rocker arm mounting studs do not incorporate a positive stop shoulder on the mounting stud These engines were originally equipped with this kind of stud However, due to production differences, it is possible some 289 or early 302 engines may be encountered that are equipped with positive stop rocker arm mounting studs Before following this procedure, verify that the rocker arm mounting studs do not incorporate a positive stop shoulder. On studs without a positive stop, the shank portion of the stud that is exposed just above the cylinder head is the same diameter as the threaded portion, at the top of the stud is of greater diameter than the threaded portion, this identifies it as a positive stop rocker arm stud and the procedure for the 351 engine should be followed. 1. Crank the engine until No. 1 cylinder is at TDC of the compression stroke and the timing pointer is aligned with the mark on the crankshaft damper. 2. Scribe a mark on the damper at this point. 3. Scribe three more marks on the damper, dividing the damper into quarters (see illustration). 4. With mark A aligned with the timing pointer, adjust the valves on No. 1 cylinder by backing off the adjusting nut until the pushrod has free-play in it. Then, tighten the nut until there is no free-play in the rocker arm. This can be determined by turning the pushrod while tightening the nut; when the pushrod can no longer be turned, all clearance has been removed. After the clearance has 1 been removed, tighten the nut an additional /4 of a turn. 1 5. Repeat this procedure for each valve, turning the crankshaft /4 turn to the next mark each time and following the engine firing order of 1-5-4-2-6-3-7-8. PATH: Engine Mechanical > Engine Mechanical Components > Valve Lash (Clearance) Adjustment > 8-289 Hi-Perf., Boss 302, Boss 429, Boss 351, 429 SCJ & 351 HO (1972)

8-289 Hi-Perf., Boss 302, Boss 429, Boss 351, 429 SCJ & 351 HO (1972)

In all cases, the preliminary valve adjustment must be done with the tappet on the low radius of the camshaft lobe. 1. Before turning the engine, make sure that the distributor is properly installed and accurately timed. 2. Locate the TDC mark on the crankshaft damper and make a chalk mark at that location. 3. Make three more chalk marks on the crankshaft damper—one every 90° of crankshaft rotation—so that the marks divide the damper into four equal segments. 4. Position the crankshaft at the TDC position as marked. Check the distributor rotor to make sure that it is in the No. 1 firing position. 5. Install and secure the pushrods and rocker arms for the No. 1 cylinder, using the thickness gauge recommended for the final adjustment. Tighten the locking nut while holding the adjusting nut (or screw) in position. If the final adjustment for your engine is a cold adjustment, check the clearance with the feeler gauge to make certain that it was not altered while tightening the locking nut. 6. Rotate the crankshaft 90° forward. Check the firing order diagram and the position of the rotor to make sure that the engine is at TDC for the second cylinder in the firing order. Repeat step five for that cylinder. 7. Repeat steps five and six until all valves have been adjusted. 8. If your engine calls for a cold tappet clearance adjustment, install the rocker covers. If it requires a hot adjustment, bring the engine to its full operating temperature and check the clearances with the engine running. Make all necessary adjustments to the clearances, stop the engine, and install the rocker covers. PATH: Engine Mechanical > Engine Mechanical Components > Valve Lash (Clearance) Adjustment > V8 With Mechanical Lifters > Except Boss 429 Except Boss 429

Valve clearance chart Click to Enlarge 1. Run the engine until it is at full operating temperature. 2. Stop the engine. Remove the rocker covers. 3. Check the ``Valve Clearance Specifications'' chart for the proper clearance for your engine. 4. Start the engine. Insert a step type feeler gauge (go and no-go) of the specified thickness between the rocker arm and the top of the valve. Adjustment is accomplished by loosening the jam nut (or locking nut)—the top nut on the rocker arm stud—and moving the adjusting nut (the lower nut) up or down as needed. When the proper adjustment has been attained, tighten the jam nut against the adjusting nut while holding the adjusting nut in position with a separate wrench. Check the clearance to make sure that the tightening of the jam nut against the adjusting nut did not alter the proper adjustment of the valve clearance. 5. When all valves have been adjusted in this manner, stop the engine and reinstall the rocker covers.