turtle-eg

I have a '95 Ls block bored .20 over to fit SRP pistons and AEM rods. My setup is LS/VTEC with a b16 gen 1 head (stock). I know the head is fine because I had it on a stock ls bottom with no problems. Now my problem is with this new block is that I get so knocking noises. My friend said it's most likely piston slap which is normal(???) on built motors, because his built motor(GE sleeved 2.0, Arias pistons, crower rods,etc...) sounds like a diesel when cold. My knocking sound gets softer when the engine warms up but it's still there. It definitly doesn't sound like a rod knock, and I reuse the rod bearings from the old rods which were for sure not knocking.

Is this really piston slap?? And is it normal for built motors??? I'm running 10w-30 oil, thinking about whiching to 20-50 to see if it sounds better.

I have been driving around like this with no problems, even 55shot NOS'ed it.

Combustion Contraption

i dont know if its piston slap but i know piston slap is not "normal" on built motors. no problem should be "normal" .

Footwork

It's normal for the most part.
Forged pistons are more dense, and thus take longer to expand.
My JUN/Cosworth slugs are the same way in the morning.
The pistons are smaller than the cylinder when cold.
The sound is gone when the engine is at operating temp because the slugs have expanded to the size of the cylinder.
HTH.

poison

Yes, that is normal when the engine is warming up. It is also known as the "forged piston purr".

The reason it makes a slapping noise when warming up is due to the piston being a little smaller when the metal is cold, and when it is warmed up fully the metal expands and seals with the cylinder wall properly after warming up to normal operating conditions.

Combustion Contraption

well i guess you learn somethin new every day. i never thought that would be considered normal. So, does this cause premature wear out on the sides of your cylinder walls or what?

turtle-eg

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by LsVtec92Hatch &raquo;</TD></TR><TR><TD CLASS="quote">well i guess you learn somethin new every day. i never thought that would be considered normal. So, does this cause premature wear out on the sides of your cylinder walls or what?</TD></TR></TABLE>

From what I heard/saw , it doesn't cause any damage. My friend's car ran this way for a year and when he changed the head the walls were nice and clean.

Dyno Queen

FLOATING WRISTPINS!!!!!!!!

go2slo96

why would you reuse rod bearings??? just buy new ones you are only asking for more problems down the road.

civicsitek GanGsTa

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by turbo gsr &raquo;</TD></TR><TR><TD CLASS="quote"> FLOATING WRISTPINS!!!!!!!! </TD></TR></TABLE>
Yup