Re: Mercruiser 120 won't stay running
Tight valves will make it run like crap.....<br /><br />======== VALVE ADJUSTMENT - ENGINE RUNNING<br />ALL GM ENGINES with Hydraulic lifters<br /><br />Following procedure should be completed only if "readjustment" is required.<br /><br />1. Run engine until it reaches normal operating temperature.<br />2. With engine running at idle, back off valve rocker arm nut until valve rocker arm starts to clatter.<br />3. Turn rocker arm nut down slowly until clatter just stops. This is zero lash position.<br />4. Turn nut down 1/4 additional turn and pause 10 seconds until engine runs smoothly. Repeat additional 1/4 turns, pausing 10 seconds each time, until nut has been turned down 5/8" to 1 turn from zero lash position.<br /><br />NOTE: This 1 turn pre-load adjustment must be done slowly to allow lifter to adjust itself, thus preventing possible interference between inlet valve head and top of piston which might result in internal damage and/or bent push rods.<br /><br />=== VALVE ADJUSTMENT -- ENGINE STOPPED<br />GM ENGINES<br /><br />INLINE ENGINES<br /><br />With valve cover removed, adjust valves when lifter is on low part of camshaft lobe, as follows:<br />Step One:<br /><br />a. Use remote starter switch to crank engine until distributor rotor points to No. 1 cylinder position and breaker points are open. Following valves can be adjusted with engine in No. 1 firing position.<br />No. 1 Cylinder- Exhaust and intake<br />No. 2 Cylinder -- Intake<br />No. 3 Cylinder -- Exhaust<br />No. 4 Cylinder -- Intake<br />No. 5 Cylinder -- Exhaust (6-cyl. Only)<br />b. Back out adjusting nut until lash is felt at push rod, then turn in adjusting nut until all lash is removed. This can be determined by checking push rod end play (up and down) while turning adjusting nut. (Figure 4) When play is removed, turn adjusting nut in 1 additional turn.<br /><br />Step Two:<br /><br />c. Crank engine until distributor rotor points to No. 6 position for 6-cylinder engine and No. 4 for 4-cylinder engine (and breaker points are open). Following valves can be adjusted with engine in this position:<br />No. 2 Cylinder -- Exhaust<br />No. 3 Cylinder -- Intake<br />No. 4 Cylinder -- Exhaust<br />No. 5 Cylinder -- Intake (6-Cyl. Only)<br />No. 6 Cylinder -- Intake and Exhaust (6-Cyl. Only)<br /><br />V-8 ENGINES<br /><br />Step One:<br /><br />a. Crank engine with starter or turn over in normal direction of rotation until mark on damper lines up with center "O" mark on timing tab crankcase front cover, and engine is in No. 1 firing position. This may be determined by placing fingers on No. 1 valve as mark on damper comes near "O" mark on timing mark. If valves move as mark comes up to timing tab, engine is in No. 6 firing position and should be turned over one more time to reach No. 1 position.<br />b. With engine in No. 1 firing position, the following valves may be adjusted.<br /><br />left Hand (Standard) Rotation Engines <br /> Exhaust -- 1-3-4-8 <br /> Intake -- 1-2-5-7<br />Right Hand (Opposite) Relation Engines<br /> Exhaust -- 1-2-5-7 <br /> Intake -- 1-3-4-8<br />c. Back out adjusting nut until lash is felt at push rod, then turn in adjusting nut until all lash is removed. This can be determined by moving push rod up-and-down while turning adjusting nut until all play is removed.<br /><br />Hydraulic lifters now can be adjusted by tightening adjustment nut 1 additional turn to place plunger in center of its travel.<br /><br />Step Two:<br /><br />d. Crank engine one revolution until pointer "O" mark and torsion damper mark are again in alignment. This is No. 6 firing position. The following valves may be adjusted as previously outlined<br />Left Hand (Standard) Rotation Engines<br /> Exhaust -- 2-5-6-7<br /> Intake -- 3-4-6-8<br />Right Hand (Opposite) Rotation Engines<br /> Exhaust -- 3-4-6-8<br /> Intake -- 2-5-6-7
