Help with knock noise

[G50911]

I noticed that on first start ups there's this knock noise I hear. It goes away after a few minutes or as the engine gets warm.

I'm very hesitant to drive it now cause I don't want to cause any more damage if this is in fact rod knock or what ever it is.

Can anyone help ID this noise?

https://www.youtube.com/watch?v=r5GHT7oTeQg

[Len 911]

Not sure maybe a Gas knock. How old is the gas? What did you do to the car last, did you mess with the engine or did this just start happining.

[FPB111]

Have you checked the valve clearances? Timing chain is usually louder at idle, rod usually sounds deeper, piston slap? Get your stethoscope out and see if you can pinpoint it.

[G50911]

gas is new. tank was cleaned and flushed before i filled it. i've been trying to get my carbs dialed in and i noticed it when i started it in the mornings it would be pretty loud. that video is not at operating temp but is not at a cold start either.

what i noticed is the #6 cylinder's plug is slightly wet and according to my carb float tool it's the weakest of the 6.

[cgarr]

Sounds like piston slap and it will go away as the pistons warm up...

[Heinz911]

You could compare to my knock movie in fourth post
Hopefully your sound is different. In my case cylinder 4 seized, possibly caused by a bore wash

[Reiver]

If you have forged pistons (Nikasils) you often hear a knock/slap when cold. Normal. Same thing happens in SB Chevy's too with FP's.
Rod knock does not go away when warmed up.

[G50911]

not sure if the pistons in there are forged. i took it to my wrench and will know a little more later or early tomorrow.

as an aside, anyone know if oil weight has anything to do with this? i put 20/50 (after a complete flush) in it and not sure if thats the same weight the PO used.

[Amstaff]

If you are playing with the carbs you can make it knock if you get a cylinder too lean. That won't normally go away as the motor warms.

[RedCoupe]

Doesn't sound quite like a rod knock, but could be a piston pin. If I remember, though, the noise of a loose piston pin changes volume aa the engine is accelerated and decelerated. The other suggestions about piston slap and a loose t chain tensioner are also very viable. Stethoscope should help.

[G50911]

valves were too tight and stuck open. compression was at 70 psi and after the valve adjustment it came back to 150 psi.

whew!!