Guest Anonymous Posted October 17, 2001 Share Posted October 17, 2001 Ok everyone, question. what's the going "looseness" of rocker arms? When the valve is all the way open, should they "rock" at all or what? I can't figure it out, and right now I have them set at just barely movable under normal hand force. when I run the car a little, and pull the valve covers off, they are all loose again. Thanks for the 411 guys. Oh yeah, I have a chevy 350 with alum heads on it. Thanks again. sean Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted October 21, 2001 Share Posted October 21, 2001 Take off the covers with the motor running. loosen a rocker till it starts ticking,Then back till it just stops, then tighten 12 turn more. I have heard that you can go a full turn, but that seems excessive to me. Oh, only tighten the nut in 14 turns at a time and let the motor come back up to speed between turns. This will be a messy job too unless you get the clips that go on the rocker to keep the oil from spraying all over. I have an old set of valve covers with the center section removed just for this purpose. Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted October 21, 2001 Share Posted October 21, 2001 Most Chev rocker arm studs have 24 threads to the inch, or about .042 lifter "preload" per revolution of the adjustment nut or polylock. A quarter turn tighter than zero lash will result in approximately a .011 lifter depression. This is plenty. The only difficulty I see in greater "preload" is that high pressure oil pumps can overload and pump up the lifter causing a high end loss of compression. Minimum valve to piston clearance should not be less than .060 just to be on the safe side of lifter pump up. As the valve and seat wear, lifter depression increases. Excessive oil pressure, rpm and lifter depression could possibly (very remote) cause a piston to valve interference problem. Hydraulic valves have a slight "reaction" time and therefore do not transfer all the lift and duration the cam has. Setting the lash as close to zero as possible will help to eliminate the pump up problem should it ever occur. Higher duration intake cams create a greater exposure for the intake valves to hit the pistons, simply because the intake valves open several degrees BTDC during the exhaust cycle upstroke. Pump up can cause bent intake valves in this instance. If you don't know your piston to valve clearance, err on the side of caution and do not use a full turn down past zero lash. It is just good insurance. I tried setting hydraulic lifters to zero with a dial indicator just to find out what would happen. The valve train as a whole was considerably noisier than I thought it should be. (lifter reaction time?) Resetting them to .005 to .010 "preload" solved the noise problem. Quote Link to comment Share on other sites More sharing options...
pparaska Posted October 21, 2001 Share Posted October 21, 2001 I'm with you Kim. I see no need to go past 1/4 turn EVER. It's wasted energy and brings on the possibility of pump up. All that's needed is enough preload to make sure there is always at least just a little. 1/4 turn is what I've always used. Top end was noticably stronger than with 1/2 or 3/4 turn. Of course, now I just use solid lifters - I like a bit of controlled clatter . Quote Link to comment Share on other sites More sharing options...
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