Rocker arms tapping
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Junior User
Joined: Jan 2008
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Rocker arms tapping
I have a 79 f150 with a 351m all stock and original. I have just changed the lifters and now some of the rocker arms are tapping and i can't get them to stop. Following a master mechanics instructions I torqued them down to 22 foot pounds. And still they tap. He told me that the valve springs need to be replaced but I wanted to ask here first to be sure. The head are the pedestal mount type. Should I rebuild the heads or try and change the valve springs? Any help would be great.
Thanks
Thanks
Lead Driver
Joined: Nov 2000
Posts: 6,648
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From: Albuquerque
Thats odd. Just the opposite should have occured, i.e. tighter lifters. Weak valve springs usually show up ant higher rpm's rather than idle. I would look for something else that changed.
Hows it running?
Hows it running?
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Junior User
Joined: Jan 2008
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Its running great. It has more power and response already. I did notice that the old lifters didn't have any "spring" left to them. I mic'ed the old and new and they were the same. Push rods are straight and free of obstructions. But the old lifters and rocker were torqued down way to much. Probably upwards of 40-45ftlbs.
Do I need a new cam? Maybe Its worn from the Over tightened rockers.
I really would like to get this taken care of, but I'm no good at trail and error stuff. My thoughts are getting a set of new heads (maybe the edelbrock ones) and a new cam.
Thoughts?
Eric
More Turbo
Joined: Jan 2001
Posts: 574
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From: New England
You need to set the preload and valve lash correctly. I wouldnt use the 22ft/lb rule here.
Tighten the rocker nut just until you feel resistance on the pushrod (ie spinning with your fingers). This you do when the lifters are bled down. Then you go 1/2-3/4 turn and your all set.
You have to do this on the flat part of your cam, in other words you do this when the valves are closed completely and lifters are on the round part of the cam.
Tighten the rocker nut just until you feel resistance on the pushrod (ie spinning with your fingers). This you do when the lifters are bled down. Then you go 1/2-3/4 turn and your all set.
You have to do this on the flat part of your cam, in other words you do this when the valves are closed completely and lifters are on the round part of the cam.
Senior User
Joined: Jul 2008
Posts: 157
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From: Mariposa, CA
The 351M has torque in place rocker pedastals, it does not have adjustable rockers w/ studs. the only way to adjust this engines preload is to change pushrod length or shims under the pedastal.
You need to set the preload and valve lash correctly. I wouldnt use the 22ft/lb rule here.
Tighten the rocker nut just until you feel resistance on the pushrod (ie spinning with your fingers). This you do when the lifters are bled down. Then you go 1/2-3/4 turn and your all set.
You have to do this on the flat part of your cam, in other words you do this when the valves are closed completely and lifters are on the round part of the cam.
Tighten the rocker nut just until you feel resistance on the pushrod (ie spinning with your fingers). This you do when the lifters are bled down. Then you go 1/2-3/4 turn and your all set.
You have to do this on the flat part of your cam, in other words you do this when the valves are closed completely and lifters are on the round part of the cam.
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