Knocking
Senior Member
Joined: 08-17-2006
Posts: 1,851
From: Ottawa, Ontario
Piston slap is when the piston moves side to side in the cylinder wall due to too much clearance between the piston and the cylinder wall, resulting in a knock or slap sound. This came about for GM when they switched to short skirted pistons (yes, apparently pistons are wearing mini skirts now
).BTW, the piston skirts in the 2007 2.4 VVT motor were redesigned:
Optimized Piston Skirt
Ecotec 2.4L VVT pistons have been redesigned with a slightly different profile. The piston skirt has been optimized with a slight barrel shape, helping to smooth its glide through the cylinder bore and reduce lateral movement. The new pistons reduce operational noise, particularly during cold starts, and enhance overall smoothness.
Ecotec 2.4L VVT pistons have been redesigned with a slightly different profile. The piston skirt has been optimized with a slight barrel shape, helping to smooth its glide through the cylinder bore and reduce lateral movement. The new pistons reduce operational noise, particularly during cold starts, and enhance overall smoothness.
Senior Member
Joined: 05-23-2006
Posts: 1,082
From: Chandler, AZ
[QUOTE=Black Rose;11457
Piston slap is when the piston moves side to side in the cylinder wall due to too much clearance between the piston and the cylinder wall, resulting in a knock or slap sound. This came about for GM when they switched to short skirted pistons (yes, apparently pistons are wearing mini skirts now ).
Thanks for that! Sounds like an Engineering "BooBoo" on somebody's part! You'd think they could have seen problem coming. 
Piston slap is when the piston moves side to side in the cylinder wall due to too much clearance between the piston and the cylinder wall, resulting in a knock or slap sound. This came about for GM when they switched to short skirted pistons (yes, apparently pistons are wearing mini skirts now
). Thanks for that! Sounds like an Engineering "BooBoo" on somebody's part! You'd think they could have seen problem coming.
Senior Member
Joined: 08-17-2006
Posts: 1,851
From: Ottawa, Ontario
It's been happening on certain V6 and V8 motors since 1999, so they have seen it coming, they just ignore it due to the amount of money it would cost them to fix it.
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