The 3800's balance shaft does a good job cancelling out these vibrations but it isn't very effective at idle speeds. Poly motor/trans mounts are very stiff and transmit a lot of vibration to the vehicle chassis, especially if you are running a solidly mounted cradle, or an 88 chassis which has no cradle bushings at all. Having done a couple of 3800 swaps in 88 Fieros, I have realized the need for an alternative.
In the past, the reason why people have chosen poly over rubber is for the durability factor. The only rubber mounts available were off-the-shelf, OE-replacement versions made for other cars which usually wouldn't fit in a Fiero application. Ones that are small enough to fit usually didn't offer a good level of durability when high engine power levels are thrown into the mix. I have done some research and come up with a new solution using an OE Fiero part... the 1984-87 engine cradle front bushings. These bushings are similar in construction to the popular poly bushings; basically you have a metal sleeve that the mounting bolt goes thru, surrounded by rubber which, in turn, is surrounded by another metal sleeve for mounting purposes. When used like the aformentioned poly bushings as motor mounts, there is no way the internal sleeve can be pulled out of the bushing; at least on the axis the engine/trans is going to apply force to this bushing and the way I have it mounted.
I just finished my latest swap using the all-new rubber cradle bushings as motor and trans mounts. Keep in mind the rubber compound used in these bushings is stiffer than OE stock Fiero motor and trans mount rubber, so it will transmit a little more vibration/noise to the chassis vs. stock Fiero mounts. However, these bushings isolate the engine/trans far better than poly or solid motor or trans mounts.
![Image](http://dtcc.cz28.com/images/bp_rubber_eng_mount1.jpg)
![Image](http://dtcc.cz28.com/images/bp_rubber_eng_mount2.jpg)
![Image](http://dtcc.cz28.com/images/bp_rubber_eng_mount3.jpg)
![Image](http://dtcc.cz28.com/images/bp_rubber_trans_mount1.jpg)
![Image](http://dtcc.cz28.com/images/bp_rubber_trans_mount2.jpg)
So the question is: Are they durable? Well, if you have a 84-87 Fiero, look at your cradle's front bushings. Chances are, they have been in there for 20 years and still haven't pulled apart or failed yet. Sure, they are probably showing signs of cracking and may have become weak over time, but consider their age and exposure to road debris and grime. There is one weakness to using rubber bushings for motor mounts, however. Rubber does not hold up well when exposed to oil or engine fluids. So to say they are bulletproof is true, to the extent assuming they never get bathed in oil. If you have an oil leak occur on the engine or trans and these fluids get on the bushing/mount, then there is a high probability they will fail. Aside from that, I challenge anyone to break one of these.
Right now the only way to get these mounts is to have me make them and install them on your car; which means you will have to bring your car to my shop. I am looking into getting these produced for sale via mail-order, but that is probably going to be some time off because of how busy I am at the moment. However, I just wanted to post this so people know there is now a "more comfortable" alternative to poly mounts out there.