Zinc and Knocking

[FlagCraig]

Will a lack of zinc in oil cause motor to start knocking?

It's a new rebuild with about 2K miles on it. She's had two oil changes with zinc additive included.

Thanks.

 

[moparnation74]

What oil are you running btw?

After proper break in period and 500 miles, No.....

 

[69Bee]

No. Improper clearances will cause this though, and it will only get worse----FAST.

 

[PurpleBeeper]

Nope. Alkyl zinc compounds are anti-wear additives used in some oil, especially "high mileage" oil, which isn't a bad idea for engine break-in.

If you have ANY knock at all, I strongly suggest you stop driving the car and figure out where the knock is coming from. Hopefully it's just a lifter that never pumped up causing one rocker/pushrod/lifter to be a little loose.

1. BEARINGS - See if you can connect a mechanical oil pressure gage. If the oil pressure is high, even after warming up, then your rod/main bearings are OK. A spun rod bearing has a very deep-sounding "THUNK, THUNK, THUNK" sound, way down in the engine.
2. VALVE GEAR - If there's something off in the valve gear, you can usually tell that the noise is coming from up top & it's more of a "clickety-clack, clickety-clack" sound....not nearly as deep, low-pitch as a rod bearing.
3. PISTONS - very old school forged pistons often had maybe .008" piston-to-wall clearance which causes "piston slap" until the engine is completely warmed up. My mid-80's TRW pistons do that.

 

[moper]

What they all said. If you can provide more details on exactly what you hear, and exactly when you first heard it that would be helpful.

 

[Garys1969RR]

Is this a steady knocking sound, or does it just occur under heavy load?

 

[FlagCraig]

It was a loose torque converter bolt. My engine builder found it.

Thanks guys for all the input.

 

[moparnation74]

It was a loose torque converter bolt. My engine builder found it.

Thanks guys for all the input.

Great news! Glad it was something simple..