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Valve coming out of adjust

980 views 10 replies 5 participants last post by  427L88 
#1 ·
So far I have had 2 valves that have come out of adjustment. Why would they do that all on there own? I'm running Comp Cam Magnum rockers with the lock nuts that came with them. Could it be the high lift cam that causes this? It's not that big at 553 intake and 578 exhaust. Will poly locks fix this problem?
 
#2 ·
Do the heads have screw in studs ? If yes, then I would look at Polylocks. Years ago when I worked at the machine shop we did get a batch of bad lock nuts that just wouldn't hold. I got sent out on one job to replace all the rocker arm nuts on a just built engine.
 
#3 ·
I wouldn't run an engine without Polylocks, as I've had the factory crimp-lock nuts back off and be the cause of additional damage. Also, the factory crimp nuts are not advised to be reused.
However, if the adjustment nuts are not backing off, then you'll be doing a cam lobe and lifter, or about to have a decent failure if a needle bearing roller lifter.

Please don't say you have a roller and crimp-locking nuts! :p
 
#4 ·
Both Ray and Steve posed good questions. My guess is that this not a solid roller lifter camshaft you have because of the relatively low lift. But if it were a solid roller cam, I would say that you need to pull the intake manifold off to inspect the lifters in question for needle bearing wear before they belch the needle bearings inside your engine and cause serious damage. But with the assumption that you have a hydraulic lifter camshaft, or a flat tappet variety, I'll point out what Ray has stated about having screw-in rocker arm studs. Because if you still have the factory pressed-in rocker arm studs instead, then the studs are very likely being gradually pulled out of the cylinder heads, and that would be a cause for what you're seeing.


If that is the case, then keep in mind that the general rule of thumb is that when you get to the .500" lift mark (at the valve) then the press-in rocker studs often won't handle the task without being pulled out of the cylinder heads, and therefore you would need to have your cylinder heads machined for the screw-in studs to prevent that, or switch to a more mild camshaft than the one you currently have.
 
#5 ·
Chris, how new is the engine? I dont know that many have this experience, but it took five to six lashings to finally get my rather aggressive UltraDyne solid cam to hold lash. And the locks werent moving. Odd but true. This on all new parts. Had my azz puckered good for a while. Now the lash never moves.

BBC I assume due to the lift? Never seen pressed in rocker studs on one.
 
#9 ·
Another one of my chores as the punk kid in a machine shop was to "Z/28" all the SBC heads we did. I think I only pinned one set, everything else went on the Bridgeport for dusting and threading on an indexed basis.

Brother it aint my memory that's failing me in middle age, hard to be "high speed, low drag" at 55. It takes max effort now, whereas before, it was just my natural state!
 
#10 ·
It's a fresh big block. 468 cu in screw in studs. It has about 500 miles on it. I'm going to adjust them all again and use poly locks. Hopefully that will fix it. Some of the lock nuts seemed to just thread right on with little resistance. I'm hoping that is all it is.
 
#11 ·
Crane used to make something called " Cool nuts" that were poly locks ( allen head set screw) for regular rockers. Are your locks like that? If so, the final step is to set that set screw, and then give the lock one more torque to set the whole. They ought not move.



( ps back in the day we double nutted a few ol LT1s that we were spinning to the moon )
 
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