Stuck Valve Indication? - Impala Tech
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post #1 of 5 (permalink) Old 08-19-2019, 03:26 PM Thread Starter
Join Date: Jan 2018
Location: Yorktown, VA
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Stuck Valve Indication?

Recently tuned up the small block in my 66 and installed new exhaust. I now have a popping sound that is similiar to a back fire. Car ran fine initally then the popping started and engine has become sluggish. At 40 MPH and above if i take my foot off accelarator the decompression increases the popping sound to a almost back fire. At idle it just pops. No knocking from underneath hence the thought maybe a stuck valve. Any suggestions on how to determine if a valve is stuck would be helpful.

Last edited by lndbarron; 08-19-2019 at 07:50 PM.
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post #2 of 5 (permalink) Old 08-20-2019, 12:05 AM
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Compression check. A bent valve will not seal and as such it will low on compression.

Big Dave
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post #3 of 5 (permalink) Old 08-21-2019, 09:52 PM
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Or possibly a cam lobe decided to take a tour of the engine?
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post #4 of 5 (permalink) Old 08-22-2019, 04:17 AM
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The above input is good and probably correct. But before you start tearing into it, check to make sure you are not running overly rich which will cause flame burning into the exhaust.
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post #5 of 5 (permalink) Old 08-22-2019, 11:43 PM
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I think a stuck valve or valve seating issue can also be seen via a vacuum gauge and you'll see the needle drop each time that bad valve hits.

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