Engine rattle under load
 

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Since it has finally warmed up I decided to give it a shot and change the right engine mount, it appeared to be paritally torn. The engine now sits about 1 inch higher, and the rattle is GONE! I still think the CAT is making a little noise, but the mount fixed the major noise. Thanks for the help everyone.
Now on to the rear end body work repair due to the uninsured teenager :x
jj

Thanks for the update. So, can you make an educated guess as to which rotating mass was causing the noise? Could it have dropped the motor low enough for it to have allowed the crank pulley to strike the frame? Or....??

That's tough. I was certain that it was a rotating mass making the noise, but when I had an assistant recreate with me observing, I couldn't see anything rubbing or rattling. This drove me nuts! I was convinced the balancer was failing, but upon replacement there was no change. I planned on replacing the cat. But I had a credit at napa worth an engine mount, so I changed it snice it looked a little rough.
Anyway, to answer the question- I don't really have a solid answer! Only other thought is maybe the exhaust was rubbing. But it sure seemed to originate from the front of the engine.
Thanks again for the input everyone!
jj