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

[914GT]

The list is getting smaller. I'm not familiar with a 6 - how tough is it to slip the belts off the fan and alternator (or anything else) then rev the engine up? (not for long of course) Just to rule-out any belts and accessories. If you have vibration down at the base motor then sure points to the rotating assembly. Double-check those mounts, try to lift the motor or move it around to see if there's any excessive movement. You've probably already done that though. Good luck Kelly I hope you find it and hope it's something easy to fix.