Confused, just swapped from 70 duro to 88 molly

[torq]

As the title says, I just swapped from a 70 duro billet RMM to an 88 chrome-molly, and I've getting a lot less NVH now. Idle below 1k now doesn't feel like I don't want to be there, I expected the opposite.

The 70 duro had about 6k kms on it, no visible damage when I took it out. A tiny bit deformed but nothing major.

What gives?

[manila]

I like my dog bone, get mounted or go home! @jbarone;

[Cheapspeed]

I have JBR's 70 and I experience almost no vibes since it broke in.

[pzr2874]

What was the 70duro RMM ?

[Mfinlay04]

Same brand of mounts?

Sent from my Galaxy Nexus using Tapatalk 2

[JBR]

Originally Posted by torq As the title says, I just swapped from a 70 duro billet RMM to an 88 chrome-molly, and I've getting a lot less NVH now. Idle below 1k now doesn't feel like I don't want to be there, I expected the opposite. The 70 duro had about 6k kms on it, no visible damage when I took it out. A tiny bit deformed but nothing major. What gives?

I bet the 70 was a little loose.

[Raider]

Originally Posted by jbarone I bet the 70 was a little loose.

I say that after visiting nursing homes.

[ABolewski]

@Raider; finally a kick ass signature that I don't have to avoid, thank you.

And yes the 70 was probably lose. Either the bolt was loose or you were hard enough on it to actually oval out the center like the SURE mounts (not as bad, probably not visually noticeable) even just a little will let it vibe the shit out of your car.

[torq]

Thanks for the insights,

I don't think it was loose, I had to rank on a breaker bar to get the vertical bolt out. It's a little bit deformed on the bottom poly, wonder if that's the cause.

Here's a pic, it's a little bit subtle, near the back edge, someone wanted to buy it off me and I don't want to screw them which is why I'm asking.

https://docs.google.com/file/d/0B__6...it?usp=sharing

[JBR]

Looks pretty much like new.

[Raider]

If you plan to sell the 70, let me know. Local is looking for one.

[JgamB]

Should've used a different duro mount.

"Some resonant objects have more than one resonance frequency, particularly at harmonics (multiples) of the strongest resonance. It will vibrate easily at those frequencies, and less so at other frequencies. It will "pick out" its resonance frequency from a complex excitation, such as an impulse or a wideband noise excitation. In effect, it is filtering out all frequencies other than its resonance."

I suspect every mod you put on your car, particularly on the exhaust side, can change your mechanical resonance.

[Cheapspeed]

I'm looking for someone to tune my mechanical resonance.

[JBR]

I still think it was loose even though the bolts were tough to remove.