piston slap

Piston slap is common in cars with cast pistons..The piston will shrink a little after it is cold and needs to warm up to expand. gm has had some issues with this in all of there vortec motors. Mostly just a noise issue but in some extreme cases it has lead to piston shirt damage and or failure. stay away from masking it with thicker oil it will starve the motor on start up and lead to bearing and ring damage..try a good oil like royal purple or Kendal..always let it warm up to allow the pistons time to reach there opp temp and let them expand....Im not to sure if your car has a cast or hyper piston in it but most cars seem to have them now..
 
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GM used hypers in the fwd V6 motors of mid 90's to mid 2000's. The problem was from the teflon coating wearing off allowing for the slap noise to become present. IIRC there was a class action lawsuit in place for the problem.. as with many others.
 
Sean said:
billy you should here my 1998 astro, fucker sounds like it has a rod knock.
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lol...and GM just keeps saying "it's fine!" To there defense though i have a buddy who worked in teh dyno lab at teh tech center. He said they got a piston slap motor in with over 300K on it and it was still within 15 horsepower from day one!

Quick question Sean, These crappy intake gaskets, would it cause a spark knock in what sounds like only one cylinder? I already know i have to replace the knock sensors and harness (i have one knock sensor not responding) I also have an in gear idle miss, feels like one consistant cylinder ALL THE TIME.
 
beesbadstang said:
Piston slap is common in cars with cast pistons..The piston will shrink a little after it is cold and needs to warm up to expand. gm has had some issues with this in all of there vortec motors. Mostly just a noise issue but in some extreme cases it has lead to piston shirt damage and or failure. stay away from masking it with thicker oil it will starve the motor on start up and lead to bearing and ring damage..try a good oil like royal purple or Kendal..always let it warm up to allow the pistons time to reach there opp temp and let them expand....Im not to sure if your car has a cast or hyper piston in it but most cars seem to have them now..
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I use 5W30 semi synthetic valvoline in mine and it seemed to keep it a litle quieter. I also let mine warm up for atleast one minute before moving it. But even when warm when you decell i can hear it rattle...i've just gotten used to it. I'll drive it untill the wheels fall off.
 
Billydroveit said:
lol...and GM just keeps saying "it's fine!" To there defense though i have a buddy who worked in teh dyno lab at teh tech center. He said they got a piston slap motor in with over 300K on it and it was still within 15 horsepower from day one!

Quick question Sean, These crappy intake gaskets, would it cause a spark knock in what sounds like only one cylinder? I already know i have to replace the knock sensors and harness (i have one knock sensor not responding) I also have an in gear idle miss, feels like one consistant cylinder ALL THE TIME.
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which motor ? what vehicle ?
 
The piston slap actually is noted all the way up to 2006 on all vortec motors not just the 4.3..... 4.8,5.3,6.0 like i said nothing was done for any of those motors they have been tested and found to be in spec....They actual noise is from excessive piston to wall clearance not just the coating wearing off....check out the ss forums...my 02 silverado has it untill it warms up..been that way for over 50,000 miles. dealer wont even look at it..My motor has a cast piston as well as most ls engines...........
 
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No forged pistons in 4.6 2v motors, they are the hyperpathetic varity and
also have piston slap issues. Here is some info I found on the web;
Hyper-Eutectic pistons, "hyper" meaning high and "eutectic" meaning melting
point are cast with a special material ( high silicate level about 12 or 14
%, the max before the metal sweats it out) at a higher temperature than
normally used in the manufacturing process. The result is a light piston
having nearly the strength as a forged piston combined with the desired
hardness and low expansion rates of a typical cast piston.
 
Sean said:
rich running engines consume oil.
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I'm assuming you think i'm washing down the cylinders and getting oil in the chamber causing my spark knock issue? The only weird thing is it sounds too consistant, like it's from the same cylinder all the time. I'm curious if the gasket is partially broken on one intake runner if it would cause that cylinder to run just lean enough to fire, but lean out and detonate under load. Using 89 to 91 octane doesn't seem to help.
 
SOrry for the highjack OP.[/QUOTE]

its cool. i dont expect this thread to fix my car.. i gotta get it in when the cash is available. probably just gonna buy a new 2v.
 
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