M40B16 Piston Slap? PLEASE LISTEN TO VIDEO

[cole45acp]

I'm dealing with a peculiar noise on my M40B16. This noise goes away entirely when the engine starts to warm up (only takes 2 minutes, longer on colder days).

The cylinder head was rebuilt, all brand new OEM parts including camshaft, springs, hydraulic lifters, rockers, stem seals, etc.
The rod bearings have been replaced
The oil pump was rebuilt, new gears and spring + new pressure relief valve.

All of this work was done to try and remedy the noise but it's still there.
The last thing I can think of to cause this is piston slap being that it goes away completely when warm.

Please listen to the video and let me know what you guys think about it. You can hear it better when I'm revving the engine. You can also hear it pretty well at 0:43 in the video.

https://www.youtube.com/shorts/d1KCmbFKb24

[Elvir]

Why you rebuilt head ? If you had any big issue while driving ?

The rod bearings symptom is knock sounds while you drive, special when you hit the gas in second gear. No matter that is cold or warm engine.

The piston slap is normal for high mileage engines.

[cole45acp]

Thanks for the reply. The head was rebuilt because the camshaft was very worn and some valve springs were broken. I have had no issues, no power loss, it runs and drives great. The noise is just concerning.

[Elvir]

What kind oil you used ?

[cole45acp]

I have tried Liqui Moly 5w-40 Fully Synthetic and now I'm trying Liqui Moly 10w40 MOS2 Semi-Synthetic (gray color oil).

[digger]

if it goes away when engine gets hot it is likely just piston slap

[cole45acp]

Yep, it goes away completely when the engine is hot. I guess I'll run it til she breaks. That could be years from now though considering I don't drive very often.

[Elvir]

I have tried Liqui Moly 5w-40 Fully Synthetic and now I'm trying Liqui Moly 10w40 MOS2 Semi-Synthetic (gray color oil).

Ok, but what oil before camshaft worn ?

[cole45acp]

I don't know. It happened during previous ownership

[aaverhulst]

How about an exhaust leak?

[cole45acp]

Nope, I’ve recently replaced the exhaust manifold gasket and smoke tested the exhaust and intake for leaks

[Elvir]

Nope, I’ve recently replaced the exhaust manifold gasket and smoke tested the exhaust and intake for leaks

How much Idle rev on that video. Is about 800 RPM ?

Also, is timing belt properly tight ? Im not sure, but in some moments on video, I hear "overtight belt" sound.

[cole45acp]

The idle is around 700-800 yes.

The timing belt should be close to the correct tightness, it was adjusted using a spring balance set to 4.4lbs (2kg) per the Bentley Manual Instructions.

[Elvir]

The idle is around 700-800 yes.

The timing belt should be close to the correct tightness, it was adjusted using a spring balance set to 4.4lbs (2kg) per the Bentley Manual Instructions.

In that case, I wouldn`t bother with that sounds. Fill the tank with gasoline and hit the gas in high rev when temperature gauge came out of the blue field. M40 love that!

[cole45acp]

Haha, will be sure to do that.