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Repair guides and support for the first generation of C/K pickup trucks.

4 Questions View all

There is a ticking/popping/knocking sound on my engine

I’ve been working in this project for a year now and swapped from a big block to a small block. Ever since I fixed the vaccum leak that I’ve been trying to find for the longest time I realized that the engine was popping( probably back firing), ticking and/or knocking. I’m not sure what it is and can’t really tell exactly what it is but sounds like it’s coming from the engine since there is no exhaust still it’s tough. I believe the engine is in the 80s and changed the oil a few months ago but haven’t driven it and only seems to do it when idling. Please help!

https://m.youtube.com/watch?v=j-Raz4LZnC...

video of engine

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Chosen Solution

Hi Daniel,

It may be a few things. The engine could be slightly out of time so one or more of the cylinders are firing out of time causing a knocking or thumping sound. Another possible issue is it could be one or more bad spark plug(s) causing the fuel to not be ignited efficiently or maybe not at all which once again could cause this sound. You mentioned the exhaust wasn’t on yet and that could mean that as there is not mufdfler on sound restriction you can hear each cylinder firing and popping. Also one more thing is to try cleaning out the carburettor with carb cleaner to ensure no deposits are restricting fuel flow,

Hope this helps! (By the way apart from the popping that engine sounds amazing :P )

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Hi Daniel,

Did you do a valve job and valve seats on that engine and does it have the valve stem seals that rotate the valves.

In the video it seems like the noise is actually the exhaust valves closing since the exhaust is off you can hear it very easily. if you put an old head with new valves and didn't do the valve seat grind and lapping, I believe you'll end up with a noise quite like this.

You said you were chasing a vacuum leak, this makes me wonder if something was left inside of the intake. At idle engine vacuum is highest and thus if inside of the intake a bolt or something was in there it would move the most at idle.

Last but not least. Using a mechanic's stethoscope, listen close to the thermostat, it may be noise from it opening and closing. If that is true you will not hear the noise when it is cold.

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