How to tell if it its a spun bearing or valve lash
10-06-2006, 07:13 PM
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How to tell if it its a spun bearing or valve lash
I just got done putting a motor in a friends car and its making a bad noise. I am not sure if its a spun bearing or valve lash.
Its a tick or similar. I shut it off right away. What should be done?
-Shane
Its a tick or similar. I shut it off right away. What should be done?
-Shane
10-08-2006, 02:13 PM
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Re: How to tell if it its a spun bearing or valve lash (vtecn8ive)
One method is to pull individual spark plug wires and listen for a decreasing intensity. If you notice that the intensity of knocking, tapping, etc. goes down when you remove a particular cylinder's ignition cable - then that cylinder is suspect.
The rationale has to do with downward combustion forces creating additional noise when there is excessive bearing clearance (which is what creates rod knock). By removing the soure of ignition from a particular cylinder, you remove this downward force - decreasing the intensity of the knock.
If you go 1 by 1 through all cylinders and there is no change in noise - it doesn't necessarily mean there is not a rod bearing issue - but the opposite (there is a decrease in noise) definitely points more in that direction.
The rationale has to do with downward combustion forces creating additional noise when there is excessive bearing clearance (which is what creates rod knock). By removing the soure of ignition from a particular cylinder, you remove this downward force - decreasing the intensity of the knock.
If you go 1 by 1 through all cylinders and there is no change in noise - it doesn't necessarily mean there is not a rod bearing issue - but the opposite (there is a decrease in noise) definitely points more in that direction.
10-08-2006, 03:06 PM
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Re: How to tell if it its a spun bearing or valve lash (clayne)
oh i c that is a good point.
Thanks.
on another note someone recommended the LMA. any input if this could be playing a part?
Thanks.
on another note someone recommended the LMA. any input if this could be playing a part?
10-08-2006, 03:14 PM
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Re: How to tell if it its a spun bearing or valve lash (vtecn8ive)
Also, do this with the car running. Just pull a plug, listen, replace, move to the next.
As far as the LMA goes - I doubt it but anything's possible.
As far as the LMA goes - I doubt it but anything's possible.
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10-06-2006 07:14 PM
