Originally posted by Vader
SBC STATIC VALVE LASH ADJUSTMENT - ENGINE ASSEMBLED OR INSTALLED

The most important step in proper setting of valve lash is providing reliable position markings on the crankshaft. Most engines with a stock timing tab and balancer should have a TDC groove in the outer ring of the balancer. It is important to verify that the groove is at TDC and hasn't slipped significantly. The TDC marker should be nearly in line with the crankshaft keyway (actually, about 7° retarded). Thus, one of the easiest ways to check this alignment is to remove the crankshaft balancer bolt and observe the keyway in relation to the TDC marking on the balancer outer ring. If the mark is relatively aligned, you can proceed. If not, you'll have to make a visible mark at the TDC position. Once you have the TDC mark verified, mark the balancer ring at a point 180° from the TDC marking. Make additional markings at 90° intervals, so that when finished you have divided the balancer into quadrants. You will use these marks to determine the positions of all cylinders through the firing order and to adjust the valves in that sequence. If you have removed the balancer center bolt, you should now replace it and torque it to 65 ft/lb - 10.5 Kg/M - 85 N/M.

Align the TDC marking with the timing tab. It is important that you use something OTHER than the crankshaft center bolt to turn the crankshaft. If you are building the engine in a stand, or have the balancer off for any reason, a crankshaft socket is indispensable. If the engine is fully assembled, a strap wrench can be very useful in turning the engine. You can also use a flywheel turning lever, or whatever suitable means other than the balancer center bolt.

Make any additional markings necessary around the timing tab to make the position more obvious, such as chalking a line on the timing tab. Remove the rocker covers if you haven't already done so. With the timing marks at TDC. The valves on the #1 cylinder will either both be closed, or the one or both will be slightly open. If either of the valves are slightly open, rotate the crankshaft one full revolution, so that both valves are fully closed. This will place the #1 cylinder at TDC in compression/firing stroke. At this position, you can adjust the valve lash on both valves on the #1 cylinder.

Start by backing off the adjusting nuts on both rockers until the push rods can be moved freely either up/down or by gently spinning the push rod under the rocker. If you are setting valves on a freshly built engine, one with lifters that may be leaking, or one with high-bleed lifters, spinning the push rod may not provide an accurate indication of the lash point, since only the lifter plunger spring may imparting force on the push rod. In such cases, checking for vertical movement is preferred. With new or unprimed (dry), leaking, or high-bleed (Rhodes) lifters, you must be very careful to determine the point at which the lifter plunger is fully extended.

When all pressure is removed, the push rods should spin or move very easily with two fingers. From this point, turn the adjusting nut clockwise slowly until the resistance on the push rod increases, or free vertical movement is eliminated. This is the zero lash point. From here, the lifter preload is applied. The factory setting specification for a stock engine is typically 5/8 to 1 turn of the adjusting nut, depending on the year, model, and your specification information source. For a higher RPM engine, it may be desirable to preload by only 1/4-1/2 turn to minimize the chance of a lifter pumping up at higher RPM and creating valve float. The lower preload adjustment on a new valve train may require an additional adjustment as the valve train "wears in" and surfaces are polished together. This is less likely on a roller camshaft engine, but can still occur. The amount of preload should be no more than 1 full turn, but the actual adjustment should be decided before you begin. If you are using jamb nuts or top-lock nuts, set the locks as necessary once the preload is set.

Once you are comfortable with the lifter preload adjustment of both valves on the #1 cylinder, turn the engine in a forward rotation (turn clockwise as viewed from the front end of the crankshaft) 90° to align the next chalk mark on the balancer with the timing tab marker. Some purists will prefer to turn the engine backward to eliminate any timing chain slack, but the typical valve timing of SBC camshafts doesn't require that amount of precision positioning.

Remember that the SBC firing order is 1-8-4-3-6-5-7-2, and that you will follow this order to adjust the valves at every 90° turn of the crankshaft. After having made two full revolutions of the crankshaft, the adjustment of all valves should be complete.