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
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
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
Are there other car companies that utilize have piston slap?
"Now Phoebe Snow direct can go
from thirty-third to Buffalo.
I back Ian here. Do a little reading on modern cast pistons and the silicon
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
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.
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.
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