Engine vibration from M-II thin motor mounts?

I'm wondering if vibration at idle with some resonance is caused by the thin rubber donuts on the aftermarket Mustang II mounts? It smooths out above idle. Engine idles about right with a Comp XE cam, new 3000 stall converter.

Lots of M-II front ends around, you guys notice a difference from the cushy OEM mounts or do I have another problem? Bought car with engine installed, had the pan off it is spotless.

 

Those Comp XE cams do idle rough . You must have a decent size cam if you have a 3000 stall . Big cams idle rough and doesn't have anything to do with the mounts unless you are runing solid mounts .
How bad is it ?

Retro Jim

 

My MII front end uses stock GM type motor mounts. No engine vibes coming through at all. But my engine is a very tame 300hp sbc with a mild cam.

 

Engine isn't jumping around at idle, looks pretty smooth. Definite low pitched vibration which goes away above idle. I've disconnected the belts, gently pried the balancer to check for end play. I'm still sorting out a 2004R install, flexplate is good. I took out a THM 350/3700 stall, vibration seemed worse with this combo, I thought that torque converter was bad. All I know about the engine is SBC 355 four bolt block, L89 aluminium heads, oil pan is spotless inside. I bought the car unfinished and don't have a base line on it.

Front end is no name sold by Southern Rods, the engine mount donuts feel very hard. I can imagine engine vibes being transmitted to the frame through them. They are nothing like modern motor mounts.

So this is not the typical situation?

 

I have a .540-.544 Cam, 351w, MII, spec says idle at 1100, anything under tends to send some vibrations. I'm for the most part solid.