My C5 has 85,000 miles and I notice the engine moves when it starts and when you give it gas in idle. I'll probably get a video of it later if I can.

But I think it's time to change the motor mounts, except that I read it's a pain. Do you need to remove the exhaust headers to get to the top of the mount bolt? I couldn't even remove the heat shield from the exhaust header with the A/C line in the way. I was trying to polish it.

Then there's the motor mounts themselves. RockAuto has them for cheap but everyone seems to be buying these super expensive motor mounts that are solid. I don't think I want the engine to rattle the frame. Then there's these http://www.ebay.com/itm/321528549628?_trksid=p2060778.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT mounts, but do they still vibrate the body from the engine? If I'm going to be doing that kind of work to the car I would want something that shouldn't fail for a lifetime, cause I don't want to do it again.

If I do the motor mounts it'll be in Spring when I won't get frostbite. So this is just planning. I was thinking if I do end up removing the exhaust headers then I might as well put aftermarket stainless steel ones. Though I hear that's a pain in the *** too.

 

I used to work a lot with urethane. According to the ebay listing they use a "Shore A hardness" urethane. Any kind of plastic. rubber, urethane is measured using a durometer with a scale of 0 to 100 There are also 3 scales of hardness. 00-A-D. The listing states these mounts have a 85a durometer measurement. That's pretty damn hard.
Here is a Durometer Scale to give you and idea of what i'm talking about and in a nut shell...these mounts are pretty hard and you'll feel some vibration for sure !

 

I recently replaced mine on my 98 w/ 120k miles.

I used the Hinson mounts and while I was at it, I went ahead and replaced the transmission mount.

The motor mounts didn't cause any sort of cabin vibrations but the tranny one did.

 

The Hinson mounts don't look too bad. Might go with those if they don't vibrate the car too badly.

But how about installation? How was it?

 

Interesting post , thanks , plus the hardness scale was cool. My car is getting to the age where rubber will need attending , so I am paying attention.

I read a lot on the forum , but have little disassembly experience or practical experience with these cars. I identified with the original posters thought to buy a part with a life of the car durability, but was concerned about vibration and noise. I know in development GM spent a lot of effort cushioning the ride with soft mounts and would not want to accidentally put on a part developed for racing and screw things up , comfort wise or in the long run worst case, transmit vibration and effect unknown other parts over time.

And then I think how much of the emphasis on a soft ride was in response to the general public rejection of the previous designs hard ride. They had deep price cuts when the C4 was new because of the ride.

So, it becomes a search for information from experience in use. I will probably go stock unless I can find enough info on advantages of other parts to convince me to switch. With the stock mount, by the time they become fatigued, I certainly won't be driving the car, I won't even be alive. Still I want to take every possible advantage if a better street car part is available. Logically , few aftermarket parts are developed for the street, because GM will get most of that business.

I will be following all of these types of posts. I have never replaced an engine mount before, and have had some very old cars. But they were not very powerful cars, so engine mounts were not as important as they would be on another , more advanced design.

 

I'll probably put stock on. It's a matter of getting them changed that concerns me. It maybe time to put aftermarket headers on, cause I'm sure to be cursing at every snapped bolt that I removed to get it replaced. Might as well put on new headers to increase performance.