poly vs rubber motor mounts

[marks86]

the Cummins in my truck uses the stock Chevy rubber motor mounts, and I can see the rubber moving a lot when I throttle it, I am unhappy with this.

what do you guys thing about poly inserts, I figure it would create more vibrating to the rest of the truck. Would this be a good thing, I would like to here from someone who has used said poly inserts

Im open for discussion

 

[skysurfer]

I can see the rubber moving a lot when I throttle it, I am unhappy with this.

Why? The rubber is absorbing unwanted vibrations which is exactly what it's supposed to do. Not trying to be a smart-ass here, but that's like saying you can see the shocks moving up and down so you want to replace them with solid steel rods.

 

[firebane]

the Cummins in my truck uses the stock Chevy rubber motor mounts, and I can see the rubber moving a lot when I throttle it, I am unhappy with this.

what do you guys thing about poly inserts, I figure it would create more vibrating to the rest of the truck. Would this be a good thing, I would like to here from someone who has used said poly inserts

Im open for discussion

If you are using stock mounts to the truck they probably need to be replaced or upgraded to something better as you are trying to use a much heavier engine than the mounts were intended for.

 

[marks86]

skysurfer- when I say the mounts are moving a lot I mean to the point where it looks like its going to tear the rubber.

firebane- that's exactly why I am asking everyone's opinion on poly bushings I wish the kit I bought used the dodge rubber instead

 

[MadOgre]

skysurfer- when I say the mounts are moving a lot I mean to the point where it looks like its going to tear the rubber.

firebane- that's exactly why I am asking everyone's opinion on poly bushings I wish the kit I bought used the dodge rubber instead

Honestly what options do you have?

 

[marks86]

poly. that's it

I would like some more info on poly inserts

 

[MadOgre]

Well I guess you have made your choice

 

[skysurfer]

So is there is a different (firmer) compound used for the rubber in a diesel motor mount? Might be possible to buy some Dodge mounts and make them fit. I was having a tough time finding the right motor mounts for my buddy's Suburban, they weren't quite right and the bolt holes wouldn't line up so I drilled out the clamshells' rivets and put the new rubber into the old shells then stitch welded them back together.

Seems to me that if poly was a good alternative then the manufacturers would be using them as oem parts.

 

[marks86]

So is there is a different (firmer) compound used for the rubber in a diesel motor mount? Might be possible to buy some Dodge mounts and make them fit. I was having a tough time finding the right motor mounts for my buddy's Suburban, they weren't quite right and the bolt holes wouldn't line up so I drilled out the clamshells' rivets and put the new rubber into the old shells then stitch welded them back together.

Seems to me that if poly was a good alternative then the manufacturers would be using them as oem parts.

the kit for the Cummins conversion uses Chevy isolators, no way to make the dodge ones work. as for your buddy's burban I bet its in between the years 83-85? that's when the changed motor mounts

 

[skysurfer]

Actually it was an '89. I changed the mounts on mine no problem but a couple years later we went to do his and after three trips to the parts house I still didn't have the correct ones. Got to the frustration point where I pulled out the mig and got creative.

 

[marks86]

heres the ones Im looking at

new style four bolt holes
http://www.amazon.com/Energy-Suspension-3-1116G-Shell-Engine/dp/B000CN74PE

old style(my style)three bolt holes
http://www.amazon.com/Energy-Suspension-3-1121R-Clamshell-Motor/dp/B000CN74S6

 

[CSFJ]

In past years I spent some time racing import cars, and a couple had been switched to poly engine mounts. They vibrate through the chassis. A lot. Even with the little tiny motors. Driving them any distance was very fatiguing. I would recommend any other option before poly mounts if you spend any length of time behind the wheel in this.

 

[CSFJ]

Now that I think of it, a friend of mine installed a set in his 4 cylinder jeep. Very noticeable difference. Not in a good way either.

 

[DoubleDingo]

If over-torquing is the issue, you could always chain down the side that lifts up under power to limit the twist of the engine. Would be a lot less expensive and still keep the rubber mounts while minimizing stress on the mounts.

I had to do that in my '56 Chevy because it had the 2 post mounts on the front of the engine and those had no stiffness to them at all. Running a 350 with a close ratio 4 speed saginaw, the fuel pump would hit the cross member. Chained it down on the driver's side, and it had about 1-2 inches of twist and then it held firm.

 

[Green79Scottsdale]

One other thing to add. If you went to poly, you would now be putting the majority of the engines torque into the frame, bypassing the engine mounts intended usage, as skysurfer alluded to.

Did GM ever use different grade rubber for different applications of the engine mounts? That might be worth investigating. Does everyone else that uses this kit have the same problems? What did they do different? (If they don't have problems that is.)