I have an LT1 and really don't know anything about LS1's but I'm curious. Yesterday I was walking out of one my classes and I saw some fat lady getting in a Silver LS1 Z28 and when she put it in gear to go it made this weird rattling sound like someone starting up a leaf blower. I'm guessing exhaust rattle but any other known problems that could cause this?

 

Piston slap can be very loud when it's cold, but that sounds more like an engine knock. Other than that, there's lots of stuff on a car that could cause rattling sounds. Next time you see her, walk up to her and ask.

 

Corsa exhausts used to have the internal baffles in the muffler break loose and they would sound like that.

-Geoff

 

I know she has aftermarket exhaust with square tips...