Loose rocker arm!
Thread Starter
Cruising
Joined: Jan 2011
Posts: 14
Likes: 0
Loose rocker arm!
So, first time out of storage for my 1968 vette, and I hear a slight clink in the engine when driving...not too bad...the next day, it is an alarming clanking sound! Take off the valve cover and find the rocker arm bolt is very loose, and allowing the rocker arm to slip all over the place. My question is how tight should I bolt it down? Seems like the others all have slight play then I try and move them by hand, should I crank the bolt down tight, or leave some play in there? Thanks!
Thread Starter
Cruising
Joined: Jan 2011
Posts: 14
Likes: 0
Is there supposed to be some slight play with the rocker arm? I tightened down the nut to almost the same height as the others, and the engin purred perfectly. Just wanted to make sure that I am not doing any damage by having it too tight...I will take it off to make sure the rod is not damaged at all though too....thanks!
Le Mans Master
Joined: Dec 2007
Posts: 6,422
Likes: 591
From: McHenry Illinois
Make sure that vavle is closed all the way, spin the push rod with your fingers as you tighten the nut. Stop when the rocker arm and pushrod touch(zero clearance), then tighten it another 1/2 turn. You may need a new locknut so it doesn't back off again.
Drifting
Joined: Mar 2011
Posts: 1,886
Likes: 9
I'm assuming you have hydraulic lifters.
With the engine idling, (and cardboard placed around the open valve cover, to catch oil), loosen the rocker arm nut til the valve begins to clatter, then bring it down til the noise just stops. Now you have set the valve at zero lash. Turn the engine off and give the nut another half turn.
That should take care of your problem for the moment. But you have to figure why it got loose in the first place. Could be:
(1) Loose nut. Chevrolet put prevailing torque nuts on the rocker arms so that they would not move. If the nut is easy to turn it should be replaced.
(2) Worn cam. Might need a new one.
(3) Pulled up the stud. You could have the (pressed in) factory stud replaced with a threaded one.
With the engine idling, (and cardboard placed around the open valve cover, to catch oil), loosen the rocker arm nut til the valve begins to clatter, then bring it down til the noise just stops. Now you have set the valve at zero lash. Turn the engine off and give the nut another half turn.
That should take care of your problem for the moment. But you have to figure why it got loose in the first place. Could be:
(1) Loose nut. Chevrolet put prevailing torque nuts on the rocker arms so that they would not move. If the nut is easy to turn it should be replaced.
(2) Worn cam. Might need a new one.
(3) Pulled up the stud. You could have the (pressed in) factory stud replaced with a threaded one.
Race Director
Joined: Sep 2004
Posts: 11,874
Likes: 263
From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
adjusting the valves is not a big deal and there are lots of good articles on doing them, i would be concerned that the rocker stud is pulling out of the head....this happened to me and i was able to fix it on the car and you can to if you are pretty well mechanically inclined and have tapped threads before....let me find the thread, bob
edit here it is....perhaps your rocker arm nut is just loosening and walking up?
http://forums.corvetteforum.com/c3-t...-arm-stud.html
edit here it is....perhaps your rocker arm nut is just loosening and walking up?
http://forums.corvetteforum.com/c3-t...-arm-stud.html
Last edited by bobs77vet; Mar 22, 2011 at 02:07 PM.
Racer
Joined: Aug 2009
Posts: 362
Likes: 72
From: Somers New York
Should valves be adjusted on a cold engine or should it be warmed up to operating temp?
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Drifting
Joined: Jun 2010
Posts: 1,781
Likes: 15
From: Oxford Ohio
If that one or any come loose again, lay a straitedge across the stud tips and see it they are level. If some are pulling out, the easiest cheapest cure will be to have a shop pin them.
Once they start coming out, they will continue, if that's what happened, as the head heats and cools and correct spring pressure is applied.
Once they start coming out, they will continue, if that's what happened, as the head heats and cools and correct spring pressure is applied.
