Piston slap???

[STI 2NR]

So I just built my first subie motor. I have built other motors in the past (honda, mitsubishi) but that was quite awhile ago.

Refresh my memory on what piston slap sounds like??? Is it a slight sound kind of like a diesel engine???

What is the root cause of noisy forged pistons??

Anyone else have similar issues??

Thanks in advance for the education.

 

[kaotic]

my built 2.21 stroker in my old wrx had some noisy piston slap. soulds like a slight knock, almost like a diesel. I was crazy worried about it at first, but after my tuner let me hear his built motor, it eased my mind a little. its because the forged pistons are slightly smaller to allow for expansion when they heat up. nothing to worry about

 

[STI 2NR]

Glad to know this. I was pretty sure the diesel like sound was piston slap. I would assume the noise is caused by the piston rocking back and forth in the cylinder?

The manley pistons I used have an offset wrist pin and are supposedly the quietest pistons in the industry.