We often read and hear about “adjusting” rocker arms for more performance. How is it done and what actually is accomplished by adjusting rockers? A quick description of the valve train will help clarify the operation.

The valve train consists of a valve (with springs, retainers, etc.,) a hydraulic lifter, a pushrod, a rocker arm with ball, and a rocker arm stud with nut. The lifter rides on the camshaft and as the cam lobe raises the lifter, the lifter moves the push rod, the push rod moves the rocker arm, and the rocker arm pivots on the stud/ball/nut and pushes the valve open. The hydraulic lifter consists of a main body, an inner body, a small spring, and a check valve. When off the cam lobe, the small inner spring expands the lifter to eliminate all clearances in the valve train, and at the same time, the lifter is refilling with oil via a small orifice in the lifter body from the engine oil feed system. When the lobe starts to raise the lifter, the lifter check valve closes and traps the oil in the lifter. By design, a small amount of oil leaks out during the lift cycle so when the lifter returns to it’s rest position, it is slightly shorter than when it started to lift. This prevents the lifter from continuously expanding each lift cycle and holding the valve open when the valve should be closed (minimizing lifter pump-up). When the lifter is back off the lobe, the cycle is repeated. Thus, all valve train noise due to loose valve train components is eliminated during all driving conditions.

All Pontiac engines are produced with non-adjustable valve trains. The rocker arm stud has a shoulder just below the rocker nut threads. The rocker nut has a mating shoulder just below its threads. Normal assembly specifies that the nut be tightened down on the stud to 20 ft. lbs. The mating shoulders of the nut and stud positions the valve train such that the lifter is in the center part of it’s travel range and it can eliminate clearances during all normal operation. The 20 # setting is not an adjustment, it simply tightens the nut so it does not come loose.

If valve train noise is noticed, it is usually due to excessive wear in the valve train components. A pressed in stud can move and cause mix-adjustment but it is rare. A stud can be hammered back down by double nutting the threaded end flush with the stud end and smacking it. Excessive noise can sometimes be eliminated by installing a locking type nut and actually adjusting it to a desired position. Do not attempt to change the position of factory type nuts! They will not stay in position unless they are locked down on the shoulder. Small block Chevy rocker arm nuts are lock type and will fit the standard Pontiac 3/8″ studs. (If 7/16″ studs are used, big block Chevy lock nuts will fit.) Aftermarket nuts containing set screws (called polylocks) work well and can be reused indefinitely. I do not recommend the lock nuts with plastic inserts due to the heat and shock in the valve train. Lifter pump-up, which occurs at relatively high RPM, causes the engine to miss and quit accelerating. Several hundred additional RPM can usually be gained by adjusting the rockers to just eliminate clearance in the valve train and then about 1/4 turn tighter. This assumes the rest of the engine can live at the increased speed, and that increased RPM might help performance. We have found that the larger Pontiac engines generally run quicker when shifted at a relatively low RPM.

The Ram Air IV engine was introduced with 1.65 rocker arms rather than the normal 1.5. If you decide to use the 1.65 arms, you must replace the stock 3/8″ rocker studs with 7/16″ studs. The stock studs will not allow the rocker arm to be adjusted down to the correct position for normal lifter operation because of the built in shoulder. Standard big block Chevy studs are 7/16″ and fit perfectly. Summit Racing has good quality units (Dorman HD.) for about $25. + shipping. I know of no way to use the 1.65 rockers with heads having pressed in studs without excessive machine work. Remember, standard Pontiac rocker arm nuts are not lock type and will not stay in position except on the shoulder of the stud.

Final Adjustment.

The actual adjustments can be made with the engine running or with it shut off (hot or cold). We prefer setting the lifters cold because it is much cleaner and more comfortable.

Adjustment with engine running.

Place newspapers between the heads and the fenders. Cover the fenders. With the engine at normal operating temperature, slow the idle to the slowest speed at which the engine will run. Remove one rocker cover and slowly loosen one adjusting nut until that rocker assembly begins to clatter noticeably louder. Oil may begin to spurt from the rocker arm. Slowly tighten the nut until the noise ceases (which is zero clearance) and then tighten 1/4 to 1/2 turn tighter. Note that when tightening the nut, the lifter has to compensate and it may hold the valve open slightly causing a miss if you adjust too quickly. The lock type nuts should stay at the final setting. If using polylocks, tighten the setscrew firmly. Set the remainder of the rockers in the same way. If several are making excessive noise when starting the adjustments, it may be necessary to temporarily tighten all nuts to eliminate the excess noise while you make final adjustments on each. Reset idle speed.

Adjustment with engine off.

Set the engine to #1 firing position. The timing mark should be on 0 and the distributor rotor should be pointing to #1 cylinder wire. In lieu of removing the distributor cap, remove #1 spark plug and feel for compression in the cylinder as the engine is rotated to the 0 timing mark. Remove the remainder of the plugs for ease in rotating the engine. Remove the rocker covers and adjust the rocker arm locknuts in the following sequence. Thanks to Pete McCarthy for defining this sequence in his book “Pontiac Musclecar Performance, 1955-1979”.

Note; The 90 degree movement is approximate. The purpose of this positioning is to place the lifter on the side of the cam 180 degrees from the lobe to assure the lifter is on the base circle of the cam.

Each locknut should be loosened during the adjustment until definite looseness (or clearance) can be felt on the pushrod with your fingers. Awhile twisting the pushrod, slowly tighten the locknut. When the first interference is felt, stop. That is the zero position. Make sure you can feel the difference between clearance and zero clearance. Further tightening will compress the lifter, although you may still be able to twist the pushrod. In any case, when you are sure of zero clearance, tighten the locknut ki to 1/4 turn tighter from the zero position and secure the setscrew on the polylocks. Replace the rocker covers and start the engine. It may miss slightly and/or the lifters may rattle until all lifters adjust themselves to the new correct positions.