urethane motor mounts, car shakes...

cisurfer · 10-15-2009, 07:45 PM

i bought the motor mounts off merican muscle and put them in today, they have 4 bolts that attach the two steel plates and inbetween them is the urethane bushing, i tightened these down all the way not knowing what else they are set at...no between 1krpms and 1500 rpms the car shakes alot...did i end up making them a solid motor mount by tightening the plates together?

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Frostbitten · 10-15-2009, 08:32 PM

there should be a gap between the top plate and the bottom plate so the urethane can flex and absorb vibration

jrherald420 · 10-15-2009, 10:30 PM

Urethane needs some break in time, the trans mount i have for my firebird and the company states break in time is around 300-500 miles. id just give it some time.

cliffyk · 10-16-2009, 04:47 AM

Then at 30k to 50k miles it will work harden and shatter. Urethane bushings, motor mounts, etc. are great for stiffening things up on race cars and weekend drivers however over the long term they don't hold up well.

That, along with general NVH consideration, is why you see the OEM stuff being made of more resiliant (and also more costly) rubberlike compounds. Using machined or cast urethane would cost a lot less, and because of that alone you can bet they'd use it if they could get away with it...

cisurfer · 10-16-2009, 10:32 AM

so if i wanna back those bolts out so the two plates arent touching....do i need to rip everything apart again to get them out?

sxynerd · 10-16-2009, 10:37 AM

I just went with solid MM.

Tim99GT · 10-16-2009, 12:15 PM

How did you like them?? how harsh was the ride?
I need to replace mine and was wondering how the solids were...

sxynerd · 10-16-2009, 12:24 PM

Solids feel like Urethane. If you have a stock K member I say 100% get the solids over the Poly. If you have a Tubular K member, there's going to be a little more NVH to consider that could possibly sway your decision. The way I see it, at that point on the mod list the car's isn't really meant to be Cadillac.

With my cams, my car shakes the walls.

Tim99GT · 10-16-2009, 12:29 PM

LOL^^ Yea, its not a DD. But i do have a PA racing K thats going in the car with cams/ect...
But i dont want it to feel like a top fuel car when sitting at a light either. I might just stick to the urethane mounts and call it a day.

sxynerd · 10-16-2009, 12:33 PM

Hell, for the price, you might want to consider just trying the solids first. You can always sell them for what you paid for them. I paid 30 shipped from egay. Poly's are $100+. If you don't mind the swap work that is.