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Discussion Starter · #1 ·
ive recently noticed a steady knocking under the left rocker cover near the rear piston on a 351 cleveland

can anyone tell me
1. what they think this might be and if im doing any damage driving around like this?

and 2. what should i be looking for when i take the cover off and is it likely to be a difficult and/or expensive fix?

thanks!




<font size=-1>[ This Message was edited by: thumpr on 5/3/02 9:47am ]</font>
 

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I've had the heel of a rocker arm hit the valve cover when a high lift cam is in the motor.

Does it "sound" like a knock or is it genuinely hitting.
I have heard bizarre things in the past but only pulling off the cover will reveal any impact with the cover if thats it.

Could a pedestal be loose perhaps?
 

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You need to check this immediately.You may have a camshaft lobe wearing flat or a pushrod with with an end wearing off.It may just be a loose rocker nut but you need to find out what it is right away because most of these problems other than the cam are easy to fix if you catch them right away but if you leave them you could end up sending metal peices all through your engine or dropping a valve and doing serious damage
 

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Discussion Starter · #4 ·
thanks for the replies.

i'm about to take the cover off now - can you give me an idea of some specific things i should look for to tell if it might be a problem with the cam/pushrod etc?
 

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Discussion Starter · #5 ·
just discovered also that the knocking is not constant - it was doing it just after startup but then could not get it to do it since.

would this rule out any of the suggested possible causes?
 

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i am not fluent in the 351 families of engines, however i do know the systems of the 289/302 engines. if the knock is intermittent you are probably looking at a hydraulic lifter problem; assuming you have a hydraulic lifter camshaft. how many miles are on the engine? is it the original camshaft? many of the Fords tend to have oil system problems. One of the first places that is affected is, in fact, the hyraulic lifters doing what is called "leak-down." the lifter allows a certain amount of valve adjusment byt he preload set on the hydraulic lifter. upon a "cold start-up" (after the oil pressure within the lifter has had time to leak-down) the lifter will knock repeatedly until significant amount of oil pressure is achieved in the lifter at which point hte knock will go away. as time wears on the lifter, the knock will become more common place, for longer time durations, and at increased RPM's.
depending on the camshaft specifics, this could require a cam change. like i said i am not well-versed in the 351's...if you could tell me the set-up i would be able to help further (hydraulic cam, roller or flat tappet, pedestal mount rockers, etc.)
 

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If it happened after first time start up on new motor it is probably a dry lifter. If it went away quick then no prob.
If motor is old (60k+) then perhaps lifter is bleeding out after resting and makes a "clacking" noise when started until oil fills it again.
Bad oil pressure, old thin oil, old lifters, new springs on old lifters etc all can do this.
 
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