400 valve noise
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Junior User
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400 valve noise
so i have a 400 in my vehicle and when i get going 50 mph or faster something starts making a noise it almost sounds to me like a chatter/knock type noise. it sounds like it is coming from the valves to me. can anyone give me any advice on where to start as to diagnosing this problem?
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Junior User
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uh yeah actually it does get a little worse once its warmed up. i have kinda checked for exhaust leaks. not really examined but just gave it a quick look over didnt see anything out of the ordinary. um i bought the motor on june 26th and it has been doing it ever since i got it. the oil is really thin and im doing an oil change this week if that would make a difference.
Postmaster
Joined: Dec 2008
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From: Southern Oregon Coast
Could be any number of things... An exhaust leak makes that kind of sound and it will get worse when the engine is warmed up...
Could be valvetrain - lifter preload, rocker clearance, etc... The 400 has a non-adjustable valvetrain so, any kind of wear or clearance issues will be noticeable.
Mine started making a slight "ticking" noise after I swapped the heads - finally figured out it's from the rockers hitting the valves - it's not terribly bad - more of a nuisance than anything, but I think doing a rocker stud conversion is somewhere on my to-do list...
Have you narrowed-down where the sound is coming from? Down low or up high? Valvetrain is noticeable as you'll hear the ticking from under the valve cover...
Your oil change idea would definitely help - well, couldn't hurt, anyway...
Could be valvetrain - lifter preload, rocker clearance, etc... The 400 has a non-adjustable valvetrain so, any kind of wear or clearance issues will be noticeable.
Mine started making a slight "ticking" noise after I swapped the heads - finally figured out it's from the rockers hitting the valves - it's not terribly bad - more of a nuisance than anything, but I think doing a rocker stud conversion is somewhere on my to-do list...
Have you narrowed-down where the sound is coming from? Down low or up high? Valvetrain is noticeable as you'll hear the ticking from under the valve cover...
Your oil change idea would definitely help - well, couldn't hurt, anyway...
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Junior User
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when im driving it sounds like it could be coming from the valve cover cause it has that kinda of echo type sound but im not exactly sure. it doesnt make the noise when im idling even at a high rev it kinda starts to make the noise but not enough to tell what it is.
Postmaster
Joined: Dec 2008
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From: Southern Oregon Coast
I would think valvetrain noise would be more consistent. I would maybe check again for exhaust leaks - just to be sure...
Just a thought, but how's the timing? Maybe what you're hearing is a "pinging"... How do the spark plugs look?
Just a thought, but how's the timing? Maybe what you're hearing is a "pinging"... How do the spark plugs look?
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yeah i could check again. i have it timed to 12btdc maybe i can back it down a little to 10 see if that helps. i just changed my plugs the other day.
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Junior User
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if i am wrong about where the noise is coming from could it be a rod knock possibly? from what i know if it was it would be consistent not just when im going 50mph or higher. it never makes the noise at any speed lower than 50
Elder User
Joined: Jan 2004
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From: Colorado
Does the noise only happen 'under load"??? If so, check your ignition timing and fuel octane rating... could be possible fuel pre ignition if its not a constant problem and doesnt happen all the time....
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Junior User
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im not exactly sure what you mean by under load. it only happens while im giving it gas and at a spd of 50mph or higher. i can be going 45 and give gas and it doesnt make the noise but 50 it does.
Lead Driver
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Get the lifter on the cams base circle and loosen the rocker nut. There should be some preload into the lifter plunger when the rocker nut is tight. You can use a dial indicator or scribe a line from somewhere on the head to the push rod without any preload. Then scribe a line with it tightened down and measure the difference with a machinist scale inbetween the 2 lines. It should be around .020-.040 no more than .060. If there is no preload then you will have a lifter ticking noise.
