Knocking noise!!!
Thread Starter
Junior Member
Joined: Feb 2011
Posts: 25
Likes: 3
From: Northern Virginia
Knocking noise!!!
My engine after warming up makes a knocking noise on the passenger side of the engine, mainly from the top of the engine. I touched the valve covers and you can feel like some thing could be touching / hitting the cover harder than the other side. I talked to a few people and they saying my “rocker arms” are bad or going out. If that’s the case what do I need to do or replace while I’m replacing the rocker arms
?! My truck is a 1977 F150 with a 351M.
?! My truck is a 1977 F150 with a 351M.
Senior Member
Joined: Sep 2010
Posts: 511
Likes: 4
From: Orlando, FL
I would think rocker arms too, but you got push rods there as well....
Usually there can only be 2 things when rockers make noise like that on our trucks. Since there is no lash- due to hydraulic lifters and bolt on rockers- that would be due to either excessive wear or a loose rocker. I would take the valve cover off. Check each rocker for looseness while on TDC for that valve. If you are on intake stroke look at intake valve while its on TDC and if you are on exhaust stroke check exhaust valve while on tdc. 20 ft lbs should be fine for rocker bolt on TDC. If you find one that is tightened to spec, but has excessive play, then you have a worn rocker, lifter, or pushrod. You probably have a roller cam and lifters and they last a long time. Check that no rods are bent. I am betting a loose rocker.....
EDIT...........Crap...I just noticed you said 1977.....I am not sure about that year. Probably flat tappets. Don't know about bolt-on rockers or not. Someone confirm???
Usually there can only be 2 things when rockers make noise like that on our trucks. Since there is no lash- due to hydraulic lifters and bolt on rockers- that would be due to either excessive wear or a loose rocker. I would take the valve cover off. Check each rocker for looseness while on TDC for that valve. If you are on intake stroke look at intake valve while its on TDC and if you are on exhaust stroke check exhaust valve while on tdc. 20 ft lbs should be fine for rocker bolt on TDC. If you find one that is tightened to spec, but has excessive play, then you have a worn rocker, lifter, or pushrod. You probably have a roller cam and lifters and they last a long time. Check that no rods are bent. I am betting a loose rocker.....
EDIT...........Crap...I just noticed you said 1977.....I am not sure about that year. Probably flat tappets. Don't know about bolt-on rockers or not. Someone confirm???
Choot em' Choot em'
Joined: Apr 2011
Posts: 34
Likes: 0
From: Laurens, sc
Well some do and some don't have the bolt on rockers. Just depends on if anybody had went throw the motor when it was rebuilt. They may have changed it to bolt on rockers or they may have left it flat tappets
Senior Member
Joined: Feb 2008
Posts: 4,658
Likes: 28
From: Henderson, NV.
Back in 1977, the 351M engines all had flat style lifters (not roller tappets), the rocker arms were held in place by a 5/16 bolt. The rocker arm pivoted on its fulcrum. After the valve cover is removed, check for any loosness in the rocker arm assemblies. Upon disassembly, inspect for wear between the rocker and it fulcrum.