i hear a tapping sound coming from the engine from time to time, always after engine is warmed up. does not last throughout drive, most of the time just for a couple miles then it stops. speed of tapping increases and decreases with engine speed. engine has maybe 600 miles on it. any thoughts??
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250 strange noise
- Thread starter skirk
- Start date
TxClassicAuto
Member
to me "tapping" and not "knocking" describes lifter or rocker arm chatter. It's just slack in the rotating assembly of the lifter-pushrod-rocke rarm-valve sequence.
If it's coming from the top end of the engine, underneath the valve cover, you just need to adjust the valve lash, and more than likely, on only several of the rocker arms.
I've had a few of these old sixes and they're notorious for that sound. Are you using solid or hydraulic lifters? If they're solid, a lot of times adjusting the chatter out means that your idle and/or overall timing might be a little rougher. Hydraulic lifters will usually take up the difference without as much consequence.
Try running the engine up to the point where it starts to chatter, remove the valve cover and see if you can locate which rocker arms are making the noise. Adjust them very slowly (1/4 turn or less at a time) until the chatter goes away. (Keep a few extra rags on hand, they will sling oil all over)
Then go for a drive, and see how it turns out...
If it's coming from the top end of the engine, underneath the valve cover, you just need to adjust the valve lash, and more than likely, on only several of the rocker arms.
I've had a few of these old sixes and they're notorious for that sound. Are you using solid or hydraulic lifters? If they're solid, a lot of times adjusting the chatter out means that your idle and/or overall timing might be a little rougher. Hydraulic lifters will usually take up the difference without as much consequence.
Try running the engine up to the point where it starts to chatter, remove the valve cover and see if you can locate which rocker arms are making the noise. Adjust them very slowly (1/4 turn or less at a time) until the chatter goes away. (Keep a few extra rags on hand, they will sling oil all over)
Then go for a drive, and see how it turns out...
TxClassicAuto
Member
Where is the noise coming from? Upper or lower? Do you happen to notice it under any specific conditions, i.e. uphill, downhill, around a corner, certain speeds/gears... and how loud is it?
Other thoughts, it could be an oil pump - if the pickup gets dry and the pump isn't lubricated it will clatter. If it's really intermittent, it could be a lifter hanging up a little and then freeing itself after a while.
For either of those, I'd change your oil just to be safe. It's always a good idea while the engine is still in the break-in period anyway.
It could also be a spark knock. Check your plug wires to make sure they aren't roasting against a manifold or anything.
Your best option is next time it happens, pull over and try to locate where the noise is coming from. Hopefully it will lead you in the right direction.
Best of luck and let us all know what you find out.
Other thoughts, it could be an oil pump - if the pickup gets dry and the pump isn't lubricated it will clatter. If it's really intermittent, it could be a lifter hanging up a little and then freeing itself after a while.
For either of those, I'd change your oil just to be safe. It's always a good idea while the engine is still in the break-in period anyway.
It could also be a spark knock. Check your plug wires to make sure they aren't roasting against a manifold or anything.
Your best option is next time it happens, pull over and try to locate where the noise is coming from. Hopefully it will lead you in the right direction.
Best of luck and let us all know what you find out.
appears to be upper engine noise. the route i drive is mostly back roads so at 40-45 never notice it. i have a short distance 3-5 miles that i need to run 55-60, its at those speeds that the noise starts. then if i pull over and turn the engine off for a minute, then restart it will go away. strange thing is i drive same route each day and doesnt happen everytime, just periodically.
also is it possible that it could be something with the points gap or ignition timing that would cause the noise. i know that plug wires can create a noise if they are arcing, didnt know if any of the other parts in the distributer could?
TxClassicAuto
Member
If you seem to notice the noise at one certain speed, I'd definitely lean toward something in valve train.
If it were ignition, you'd probably notice it only at low speeds, once your plugs heat up, they should ignite easier, even without solid current. Just for kicks and grins, I would pull the distributor cap and check the point gap and replacing a condensor is cheap and easy.
But more than likely, I'm sorry to say, you may have to pull the pushrod covers off the side to check and make sure a lifter isn't sticking. In fact, if you painted the block without the covers on, make sure paint isn't causing the lifters to hang up, you may want to check for burrs in the lifter bores too.
The intermittent nature would make me think it's something minor if it's not too loud. And speaking of noise and volume, you can actually listen inside the valve cover and push rod covers with a mechanic's stethoscope, or even hammer handle. Your metal covers act like a bell and will amplify the sound to help you locate the source.
If it were ignition, you'd probably notice it only at low speeds, once your plugs heat up, they should ignite easier, even without solid current. Just for kicks and grins, I would pull the distributor cap and check the point gap and replacing a condensor is cheap and easy.
But more than likely, I'm sorry to say, you may have to pull the pushrod covers off the side to check and make sure a lifter isn't sticking. In fact, if you painted the block without the covers on, make sure paint isn't causing the lifters to hang up, you may want to check for burrs in the lifter bores too.
The intermittent nature would make me think it's something minor if it's not too loud. And speaking of noise and volume, you can actually listen inside the valve cover and push rod covers with a mechanic's stethoscope, or even hammer handle. Your metal covers act like a bell and will amplify the sound to help you locate the source.
jaybyrd66
Member
feels good to be able to do that from time to time huh? lol
drabo
Member
I used to buy the cheap alum/paper exhaust manifold gasket and they would blow out after a couple years. I got tired of replacing it so I sprang and got a copper gasket. I reused it when I tore the motor down 1.5 years ago and still no leaks. It was well worth the money.
