Pistons knock(turning by hand)

[splitfire]

Hello.

What can be the cause of such knocks?
All pistons knock in TDC

j2k7S2CLQ88

[justinbyrant]

sounds like piston slap, was this all recently machined?

also turning it over by hand is deceptive as free floating pistons moving in the block are going to do different things than they will with oil lubrication, compression, and actually being moved by the force of combustion instead of being moved by the crankshaft being turned, different forces, different noises

[KAT-PWR]

Too loose piston/wall clearance

[splitfire]

Yes, bores were machined. But the pistons hardly fit to bores, P2W clearance is 0.04-0.03mm(0.0016-0.0012")

P.S.
When crank is being turned by electric drill, knocks disappear

[KAT-PWR]

Also it is cold. When it heats up it'll probably be fine if you know you set p/w clearance.

[splitfire]

One more thing.

When a piston is a bit after TDC, and I press it with hummer handle, it moves down a little. Movement is very small, but it takes place.

[jedi03]

Did anything get measured before assembling?

[Frank_Jaeger]

It sounds like there's looseness in the wrist pins. I.e. after the piston goes all the way up, there's a small delay before the rod starts to bring the piston back down. Or perhaps looseness between crank journal and rod.
Considering it does this at TDC for 1&4 and also 2&3, it would make sense... seems like it's something consistent.

[anti tyler]

It sounds like there's looseness in the wrist pins. I.e. after the piston goes all the way up, there's a small delay before the rod starts to bring the piston back down. Or perhaps looseness between crank journal and rod.
Considering it does this at TDC for 1&4 and also 2&3, it would make sense... seems like it's something consistent.

I agree on this but it's tough, it does sound like the pins.

However that's kind of just like a partial possibility

[splitfire]

Rod bearing clearances were verified with plastigage today, everything is within specifications(2nd rod clearance is about 0.045mm, other rod clearances are 0.025mm)

Wrist pins are tight enough:
oiled pin slowly slips out of rod bushing under it's own weight;
pin can be inserted into the heated piston only.

I've run out of suppositions :(

[cotbu]

XD! That's not even a knock sound, or slap, but anywho.

Sent from my SM-N910T using Tapatalk

[jedi03]

is there a lip in the piston wall?

[splitfire]

is there a lip in the piston wall?

Unfortunately I haven't understood the question, but here are pics of pistons:

http://storage2.static.itmages.ru/i/16/0729/s_1469808519_5178597_1a433430b7.jpg (http://itmages.ru/image/view/4659431/1a433430)
http://storage1.static.itmages.ru/i/16/0729/s_1469808511_2243629_50d7c49603.jpg (http://itmages.ru/image/view/4659430/50d7c496)