On Wed, 15 Jun 2005 14:57:39 GMT, "Steve" >
wrote:

>I've never heard of a manifold cracking due to back pressure. Since air is
>compressible, then the "back pressure" would build up and effect performance
>to the point of killing the car.
>Heat problems, poor mounting, bad motor mounts may be causes.

Strange. I'd always attributed this to my "heavy-foot" driving style.
As a point of reference, I also had a crack in the exhaust manifold in
my previous vehicle, a Jeep TJ 4.0L.

Thanks, for you input, though.