Can rubber engine mounts go hard after many years?

[Circlotron]

Trying to make the 5L VP all quiet and shooshy inside like a limo. At around the 1500 rpm mark there is a drony, moany kind of sound (pretty sure not exhaust) that might actually be coming from the p/s pump though when you listen to it with the bonnet up it is not really that noisy. You can hear it in the car like it is coming through the metalwork. It is not loud or anything, just you can hear it. What I am wondering is, seeing the rubber engine mounts are nearly 20 years old, can they gradually go hard and inflexible and so transmit more vibrations and noise to the car structure?

[immortality]

rubber certainly does age. i'd look at the exhaust mounts also for noise transmission

[EDGE3]

Im not sure but arent the engine mounts hard when they are new and over the years they become softer and start to split

[immortality]

i though rubber hardens with age and then becomes brittle and starts to crack

[Circlotron]

Well now I've got new engine mounts and what a difference! When you sit at the lights for example you can barely feel the engine idling. The moany sound has shut up quite a bit too. One thing that is still there (but much reduced) is about 1500 rpm even in neutral, a (slight) shaky vibration. I noticed that the crankshaft pulley doesn't run exactly true - it is about 1/2 mm off centre so would this be enough to put things off balance? Could someone else with a 5L go outside and give there car a little rev slowly up and down in the 1000-2000 rpm range and see if this vibration is a common thing or not? If it is the same with all 5Ls then I'll just have to live with it, otherwise I'll see about taking the pulley off, bolting it to a dummy harmonic balancer and sticking it in a lathe and see if it can't be trued up a bit.

[Circlotron]

Looks like the pulley is a little bit crooked, not eccentric.
The further you go out from the harmonic balancer the wobblier it gets. The innermost groove for the a/c belt hardly moves at all but the outer one moves 1/2mm. Maybe there is some dirt or stuff between the face of the balancer and the pulley, or maybe the first bolt was done up real tight so it is pulled over a bit, then the other three done up.