wierd resonance, anybody else have this? Options

[blabla914]

OK. I'm going to try to make a long story short.

Last winter I did a six conversion to a 2.0L six with a rich johnson front mount with the club sport mounts. I am also using club sport mounts at the back. I originally fitted the car with a sport muffler. I finally replaced the sport muffler with a Bursch a few weeks ago. While the sport muffler sounded great I tired of my ears ringing for about 20 minutes after getting to/from work. I'm surprised my neighbors weren't throwing rocks at me, especially on those early sunday mornings on my way to an autocross.

Now that I've got a muffler that actually muffles I've noticed the car has a bit of a resonance at precisely 1900 and 2300 rpm. You kind of hear a waaaaaaaaaaa type noise and you can feel a little vibration.

Is this just the hard mounts transmitting some vibration to the car and resonating at these specific rpms or do you think I really have a problem?

Thanks for your help.

Kelly

[blabla914]

Good question. Thanks for the response.

Yes, the same noise is made in neutral with clutch in or out. This leads me to believe it's somewhere in the motor. I don't like that.

The crank itself was not rebalanced or cut from stock. It is a forged CW crank from a '69 E motor.

The rods were all weighed and assembled with the lightest on 1 and 3 next on 2 and 5 and heaviest on 2 and 6 or however you are supposed to do it according to Bruce Anderson's book. I also weighed all the pistons to make sure they were in spec.

The clutch and pp are directly off my 4 cyl which did not resonate like this.

The flywheel was cut and rebalanced by the same house that used to balance all my engine speed sensor test targets. I used to work for Siemens VDO automotive making engine speed sensors and we used to make some really out of balance test targets. These guys would balance them so I could put my coffee on the test rig running 8k, so I'm pretty confident in their work, but it is possible they messed up.

I'm also DAMN sure the flywheel is tight with new bolts and red loctite. The pp bolts are also torqued to spec with blue loctite.

Is there anything I've overlooked??

Kelly