Road Runner Nest

well, after about the last 2 months of tearing apart the RR, she's up on the rotisserie! stripped to the bone.

came accross this goody- never seen one before.

73 RR pic one is inside- small plate with three flat bolts welded to the tunnel.

pic two is in the tunnel with the three threaded bolts sticking out.

looks factory- almost like something for a driveshaft loop.

John Mac

mounting plate for a harmonic vibration damper

Eric, I dont mean no disrespect.

Harmonic Balancer (vibration Damper)
The harmonic balancer, or vibration damper, is a device connected to the crankshaft to lessen the torsional vibration. When the cylinders fire, power gets transmitted through the crankshaft. The front of the crankshaft takes the brunt of this power, so it often moves before the rear of the crankshaft. This causes a twisting motion. Then, when the power is removed from the front, the halfway twisted shaft unwinds and snaps back in the opposite direction. Although this unwinding process is quite small, it causes "torsional vibration." To prevent this vibration, a harmonic balancer is attached to the front part of the crankshaft that's causing all the trouble. The balancer is made of two pieces connected by rubber plugs, spring loaded friction discs, or both.

When the power from the cylinder hits the front of the crankshaft, it tries to twist the heavy part of the damper, but ends up twisting the rubber or discs connecting the two parts of the damper. The front of the crank can't speed up as much with the damper attached; the force is used to twist the rubber and speed up the damper wheel. This keeps the crankshaft operation calm.

You must mean something else?

It looks like something for the drive shaft?

Eric wrote:mounting plate for a harmonic vibration damper

Correct. It's a weight actually on the underside on the tunnel. Found on 71-4 non hp B-bodies. Need any more of them?

They found late in the 71 model year that the harmonics in the driveshaft tunnel were too loud. I have a dodge TSB from 1/27/71 that calls it a "floor pan boom damper". It is meant to reduce the low frequency road and tire noise that sounds like booming. As Mark said, it was found on the non HP B bodies.

This car is a '73 340 4-speed car, not a non high performance and it has the damper. My '71 GTX does not have it. As the car is a high performance, , you have me a little confused.

Eric wrote:They found late in the 71 model year that the harmonics in the driveshaft tunnel were too loud. I have a dodge TSB from 1/27/71 that calls it a "floor pan boom damper". It is meant to reduce the low frequency road and tire noise that sounds like booming. As Mark said, it was found on the non HP B bodies.

Interesting info.

71440 gtx wrote:This car is a '73 340 4-speed car, not a non high performance and it has the damper. My '71 GTX does not have it. As the car is a high performance, , you have me a little confused.

All the 71-2 BB HP cars that I've had did not have the damper. I would have thought that a 73 340 car would not have it either being how it's a HP car. Maybe just BB hp's didn't have them. I've had 318, 383 and 400 2-bbl cars that had them.

71440 gtx wrote:This car is a '73 340 4-speed car, not a non high performance and it has the damper. My '71 GTX does not have it. As the car is a high performance, , you have me a little confused.

Sorry, should have said they didn't come on 383 4bbl and 440 cars. Probably didn't bother with those because the exhaust was loud enough to mask the sound

ok

Links to the three page TSB;

http://www.hamtramck-historical.com/ima ... ge%201.jpg

http://www.hamtramck-historical.com/ima ... ge%202.jpg

http://www.hamtramck-historical.com/ima ... ge%203.jpg

Hey Barry
You wouldn't happen to have the Plymouth version of this TSB would you? Did they even issue one?

Hi Eric,
I got about 1000 1968-1974 TSBs in the mail last week. I will keep my eyes peeled as I get them sorted out. They are all mixed up.

Barry

Well, I learned something new,

thanks guys!!!! but since there is none there now- there won't be one when I'm done!!!!!!

maybe i'll make a driveshaft loop out of it!!!