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305 piston slap


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Hi guys,

My uncle bought a 96 chevy truck with a 305 and 110,000 kilometers.

It makes a ticking sound when running.

Aparently due to the short piston design, the piston skirt slaps the cyclinder wall. This makes a ticking sound. Anyone out there famliar with this? Any information on how to combat this problem would be great. Thanks

Jonesy

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Piston slap sounds more like a diesel engine sound and gets quieter when the engine warms up. It is caused by a loose fitting piston. Short piston skirts can make the problem worst.

 

A ticking sound is normally an old lifter, or low oil pressure, in need of a rockerarm adjustment, worn cam, or exhaust leak. and normally gets louder as the engine warms up.

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I forgot to give the cure for piston slap.

 

Bore the engine and install new pistons. Make sure the machine shop knows what they are doing (quality shop). The shop should not bore the block until they measure the "new" pistons you are going to use. The use of torque plates during the bore out process will also make a big difference in engine "build quality". A backyard hone job and new rings on old pistons is the most common cause of piston slap.

 

That is why forged pistons are loud when the engine is first started. More "cold" clearance is required for forged pistons because they expand more than cast pistons when they get hot. So when the forged pistons are cold, they rock in the hole which causes the skirts to slap the cylinder bores.

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Rebuilding the engine is out of the question at the momement. The truck runs great except for this problem. Anyone have any experience with an oil additive or product to fight this problem. Obviously you can't eliminate this without rebuilding the motor but any ideas that might help quiet it would be greatly appreciated, thanks.

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The GM "Piston Slap" problem is all over the news and internet with the government looking into it and the lawyers starting class action suits. Although it's for later trucks (1999 and up) when they changed the piston design. I'd suggest you do some searching and reading.

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