rocker arm not moving...........
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New User
Joined: Feb 2014
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From: Seattle
rocker arm not moving...........
The 390 FE in our F100 was claimed to have been rebuilt by the previous owner. This week it sounded like it had a miss and lost power. White smoke came out the exhaust. I assumed we blew a head gasket. I did a compression check and found two cylinders on the drivers side were low. I pulled the valve cover to inspect, and 3 of the 8 rockers are not even moving. Where do I go from here? How do I determine what's broke, and why it broke? Is this a top end only issue, or do I potentially need to pull the motor? Thanks in advance for your help, Mike and Dane
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A number of things could've happened. Cam lobe flattened out, bent pushrods, collapsed lifters... I would pull the intake and see whats moving or not moving when the engine is rotated by hand. Most can be done without removing the engine but who knows what damage was done if there's metal shavings in the oil. This could be simple as just a couple pushrods or could turn into a total rebuild.
Cargo Master
Joined: Sep 2005
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pull the rockers that dont move and pull out the pushrods, see if they are straight, if they are put them back in the lifter and hold them with your finger and see if they go up and down when you crank the engine. If they don't go up and down the cam is shot, if they do, the lifters could be deflated. If the pushrods are bent and you didn't over rev it, it more than likely jumped a few teeth on the timing chain.
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From: Seattle
Correct the rods are not moving. I have not pulled them to see if they are bent. Will do that tonight.
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New User
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From: Seattle
pull the rockers that dont move and pull out the pushrods, see if they are straight, if they are put them back in the lifter and hold them with your finger and see if they go up and down when you crank the engine. If they don't go up and down the cam is shot, if they do, the lifters could be deflated. If the pushrods are bent and you didn't over rev it, it more than likely jumped a few teeth on the timing chain.
The motor will still start and run in it's current condition. Will a timing light tell me if it jumped time? Or should I not start it again until I diagonse the problem? How would I know if it jumped time?
Hotshot
Joined: Mar 2013
Posts: 14,255
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From: Phoenix, Az.
Jumped time will not cause the lifters to not move the pushrods. That would be another issue. And no, I would not start it untill you solve the issue at hand. 1st see if the pushrods are bent and then we go from there.
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New User
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From: Seattle
I don't know if the cam was upgraded by the previous owner.
I would still like to understand what a deflated lifter is if someone want's to chime in.
Going home now to pull and inspect the rods, will report their condition later.
Thanks
I would still like to understand what a deflated lifter is if someone want's to chime in.
Going home now to pull and inspect the rods, will report their condition later.
Thanks
Fleet Mechanic
Joined: May 2012
Posts: 1,724
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From: peru kansas
when something like this happened to me it was the valve guide seals (little plastic/rubber things you can see through your valve springs) after they had set for 10 years without running they had dry rotted and busted all to pieces unknown to me i kept driving it and was having oiling issues due to all those little busted up pieces clogging my oil return ports in the heads and who knows what else it started running doggier and doggier and missing like crazy and i had 3 cylinders completely dead and a few that would barely even open the valves the cam lobes were wiped so bad, but that 352 still made her final voyage to her resting place RIP smokenchoke you died so others could live......... after that little rant did you by any chance see any of the little chunks of bs? or did the motor sit a while in between use?
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If the pushrod is not moving when the motor is turned over, the problem is either the pushrod is bent and jammed in the head keeping it from resting on the lifter, the lifter is collapsed or jammed in its lifter bore keeping it from riding on the cam lobe, or the cam lobe itself is worn down and not pushing the lifter up in its bore. If the cam is worn down you will have alot of metal shavings in your oil and running it any longer will cause severe engine damage. Pull the oil filter and see if there is metal shavings or the oil looks metallic. Worn cam lobes are mostly caused by cheap cams or improper break-in when the cam was installed. Jeffafa is right though.