lately i've started to hear a slight knocking noise from my motor on cold starts and goes away after its been driven and warmed up. at first i thought it was rod knock but it would go away. I did check all my bearing clearances and it was within spec. now i think its my pistons rattling around when its cold. i have wiesco pistons 12:1 cr on eagle rods. wiesco suggested .0026" clearence so my machinest took off .002 for clearance and did not account for the .001 for the side skirt coating which gave me a .003 ptw clearance. will that cause my pistons to rattle on a cold start?

 

have you measured it to be certain? If ptw is a little on the large side, piston slap at cold start definitely seems plausible.

 

i didn't measure it. the machinist said he took off .002" for clearances. i saw him measure the piston and then he said he'll take off .002" from that. i said i guess he knows what he was doing. but then i don't think he works with honda's much and really knows what he was doing. so then when i went to pick up the block and pistons he said i took off .002" i took his word and then i knew that you're not suppose to measure the piston with the coating or suppose to take off .001" from the measurement.

so i took it to another reputable shop and he told me that the clearance was bigger then .0026". so i was like wtf. he said it was okay to use it but it might rattle.

didn't notice the noise until one early morning. the motor has about 800 miles on it never seen anything above 4000 rpms. crossing fingers its not rod knock...

 

why hasnt it seen above 4000 rpm yet?

without knowing the exact ptw, you are going to be working off of speculation.
If the bore is too large, it likely is piston slap being that it doesnt make any noise when its warm.

can you explain the rattle sound better?

 

it just sounds like a faint knock in the background. like kind of like hearing your front door knocking when your in your room. then when it warms up its not there anymore.

 

if its properly assembled, its typical to get knock from forged pistons when cold.. you gotta remember they expand more than cast pistons..