okay, so ive been breakin in the new motor. But today it started making a unusual sound. Like the pistons were hitting the bottom (this is my best guess, not sure if it is actually doing that) Its more distinct in 1st gear. The sound isnt horrible loud or anything, its almost like a very slight rumble. Im guessing its the sound that pistons make when the rings get somewhat seated (the new engine has about 150 miles on it so far) They are CP pistons, 87mm if that makes any difference. Anyone else notice this after getting their engine built, and is it normal or should i be concerned?

 

i tried to make a video to capture the sound, but it didnt pick it up at all. Its best described as a fluttering sound

 

good lord 87mm? why so big?

 

Might be an H-series block

 

ever heard of piston slap? It's common when using forged internals