Ruh Roh!
You say you can "feel" it...is it a noise, or a vibration....or both?

It's both Joel. I've been hearing it for the last 400 or 500 miles. It sounds like a diesel a bit if that is a good description. The oil pressure is right on 40 psi, temp stays around 190 to 200 but every time the revs get over 2000 I can hear it and today when I put my hand on the engine I could feel it too. It idles just fine and is smooth below 2000 rpm. At first I thought the sound was coming from the rear end or the tranny but the noise is there in park.

|UPDATED|7/16/2013 10:15:17 AM (AZT)|/UPDATED|

Did ya maybe get some crappy gas recently? The "sounds like a diesel" points to spark knock/ping. Is your distributor tight? Perhaps it has moved counterclockwise, advancing the timing too far. That would cause the noise and a rough idle/vibration....

I checked the distributor hold down, it's tight. Lugged it up some hills, no noise and it's 90 F outside today and very humid. 3 tanks of gas through it at least. Using Shell premium. Timing is set at 12 degrees. Running ported vacuum. Total timing is 34 degrees at 3000. I don't think it's knocking. When I say diesel, I mean it has that growl. Another description from inside the car is the sound of a playing card in a bicycle spoke amplified 10 times. It's getting worse. I can now hear it at highway speeds even with the windows down and the tops off. I uses to only hear it when the car was closed up. The sound is constant when I'm on the gas and goes away as soon as I let off or at the very least diminishes in volume. I can drive it all day if I stay in town and it sounds fine as long as I accelerate below 2000 rpm.  

|UPDATED|7/16/2013 10:52:13 AM (AZT)|/UPDATED|

Wow....hard to say what it could be, without actually hearing it, but it may be a rocker arm, or lifter failing, could be that something has gotten on top of one of the pistons(carbon, etc)....so many possibilities. Is there a chance you could get a video, and post it somewhere, so we can maybe hear it?

Not to sound overly simplistic, but, could it be the pcv valve?? or, some other vacuum related noise?... maybe a line collapsed,brake booster line?... just a thought?? 

Someone else mentioned to me that it may be carbon... Dunno.

If you know which side is making noise. Take the valve cover off, cut a 6" wide card board insert in valley to stop oil from getting all over. Start engine and watch rockers for movement. If some are not moving much, I would say cam and lifters are bad.

Try an automotive stethoscope if you can get your hands on one. This was the only way I could find a tap in my engine which turned out to be the fuel pump arm hitting the block.