Piston Slap

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Doesn't sound like a data driven decision to me.
Brian
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NJ Vike wrote:

This is nothing new. It comes up on the newsgroups every now and then, but the problem has been around for years.
There are many factors, but the main one is that GM and others went to short skirt pistons years ago in a bid for lower drag, better fuel economy...etc. The short skirt pistons will rock in the cylinder bore when cold and that's what you hear. Once the piston has warmed up and expanded to its normal running size, the noise goes away.
We have not replaced any pistons in the new gen v-8 small block in an attempt to correct the noise. Some other dealers do, but I think it's nothing but a patch anyway....the new pistons are the same design.
It doesn't affect reliability....it's just annoying that your nice new truck sounds like my 20 year old K-car.
Ian
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I first heard about this with Ford Expedition 5.4 V8, which I have, when I first heard this sound. I have also heard the same story about not effecting either the performance or causing damage to the vehicle but for *me* this is not acceptable.
Are there other car companies that utilize have piston slap?
Ken
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<snip>
I back Ian here. Do a little reading on modern cast pistons and the silicon alloy content.
http://en.wikipedia.org/wiki/Hypereutectic_piston
I owned a Mitsubishi loose tolerance 3.0L V6 engine that rattled like a diesel from piston slap when started cold for the first few minutes. When I pulled the heads to freshen everything up @ 146,000 mi., there was some scuffing in the cylinder bores but no other problems. I could still see the hone marks in all of the cylinders even in most of the scuffed area. Once buttoned back up, compression was at 96-99% of spec on all cylinders. The next owner is now past 200,000 mi. on the stock bottom end and still going.
The 5.7L V8 Vortec in the 97 'Burb had a touch of it and the 4.7L V8 IForce engine in my 04 Toyota has it too. Once the engine comes up to operating temperature, the pistons expand and it goes away. When cold, I just take the scenic route out of the neighborhood in 2nd for the first minute or two and things are warm and ready to go when I need to get on it to merge into traffic.
If you are really concerned, start doing engine oil analysis at every 10k (or every other oil change) to establish a trend line. If you do have a problem with rapid piston wear, it'll show up in the analysis plots and you'll have a stronger position with respect to a documentation trail to seek redress from the manufacturer.
http://www.blackstone-labs.com/gas_engines.html
Blah
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Not advertising or condemning this site, www.pistonslap.com but you can get some info here on piston slap. I believe it's just a little biased, but you can Google GM piston slap and get tons of articles.
Brian
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Brian,
Thanks for the link. I will look into it.
Ken

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The Expedition is a Ford. They use yardsticks instead of micrometers for measurement. Fords are noisy!

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