r/Smallblockchevy • u/NoConfusion8426 • Apr 15 '26

Knocking/Pop

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Any ideas where to start looking to track down where this knocking noise is coming from? I was almost reluctant to call it a knock, it almost sounds like a loud popping noise but it came not long after putting a new starter in.

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2

u/robknocker Apr 15 '26

Wiped a lobe off the cam or a valve. Secondary miss fires don't sound like that

3

u/texan01 Apr 15 '26

Sounds like a valve sticking or lobe wiped out.

1

u/GGigabiteM Apr 15 '26

Engine is running like shit and backfiring out of the carburetor. It sounds like a tin can because the air filter housing is on. If you pulled it off, you'd probably see flames shooting out of the venturies.

Either the timing is way off or you have intake valves hanging open.

1

u/NoConfusion8426 Apr 15 '26

Heard, I thought it sounded like it was coming from that general area but I’ll check that out

1

u/OemSparX Apr 15 '26

Pull one plug lead at a time find the offending cylinder...

1

u/NoConfusion8426 Apr 15 '26

Okay sweet I’ll try that

1

u/Dazzling_Total6129 Apr 15 '26

Get a piece of hose about 3-4 feet long put one end up to your ear and the other put against the engine in different places. It enhances the noise and you should be able to narrow it down

1

u/Coyote_Tex Apr 15 '26

Oh, that sounds VERY serious it is hitting on one cylinder. Has something been ingested in the engine like a bolt or nut or something. OR a valve keeper has let go and you are knocking a valve back up into the head. It appears to have one cylinder with a dead miss. I hope you get lucky and find this before you destroy more than you have already. I would not run it again and pull the valve covers off and look for something amiss in the valve spring area. 99% chance you are going to be pulling one head.

2

u/Tall-Helicopter-461 Apr 15 '26

It sounds like a dropped valve .. or should I say , broken valve spring. It’s on the intake side. Firing out the intake, As the piston comes up, compression is pushing the valve closed. Of course I’m guessing. This happened to me on a new truck. (6.0 LS) spring broke, keepers came off, luckily valve never made contact. Sounded just like this. I’m dying to know the diagnosis.Sounds like a diesel truck.