You can probably purchase hard polyurethane motor mount inserts for your car from Energy Suspension or Prothane. However, Windo Weld is cheap, available at most auto parts stores, and hardens to a much softer (rubbery) filler material. This means you get most of the benefits of inserts or solid mounts, without all the vibration.

Many cars aren't designed to handle horsepower upgrades, racing clutches, and other modifications which put more stress on the motor mounts. The flimsy mounts on most factory vehicles are like rubber bands, and this often causes severe wheel hop which damages your transmission. By filling the empty spaces in the mounts, the motor is held in place so it can't move around and contribute to unwanted oscillations which occur when launching a car hard (particularly in front wheel drive cars).

My '97 Eclipse was an extreme case (could not even spin the tires without hopping), but I'm not the only DSM owner with wheel hop problems. Road Race Engineering clued me in to a very inexpensive solution. For me it was the miracle cure! The reason I put this page here is because so many people have asked me about this modification.

This is a simple (not necessarily interesting or technically correct) explanation of wheel hop:
The suspension and engine are connected to the rest of the car with flexible, rubber bushings and mounts. This flex kills vibrations, but it also produces a secondary, unwanted, oscillatory mechanical system. Normally, this system isn't acted on in such a way that it oscillates. When launching, the weight transfers to the rear of the car, reducing traction in the front. As the front tires break traction, the forces on the suspension and engine also change, setting them into motion. When the tires grab again, the forces change back the other way, now applied to a system already in motion. Now we have an oscillating force applied to an oscillating system, much like a hitting a paddleball. If you apply force to the paddle to match the natural frequency of the ball attached to the elastic string, you can keep that system going all day. With wheel hop, the motion of the system feeds back to the wheels, causing the oscillating force to sync up with it. This will also go on all day (until you reduce throttle or the transmission falls apart).

The solution is to reduce the flex in the rubberband-like motor mounts and suspension bushings. This page deals only with the motor mounts.
Mike at RRE told sent me a tube of Windo Weld. This is a cheap way to convert the flimsy stock mounts (referred to as roll stops in the manual) into solid ones. This cuts wheel hop and protects the mounts from premature wear, and more importantly the transmission. The stock mounts have huge gaps which allow the center of the mount to move up and down excessively. The Windo Weld is a soft, rubbery polyurethene that closely matches the consistency of the rubber part of the mount, and is a perfect way to fill those gaps.

Do this in thin layers! I scrapped the first attempt because I filled the mount all at once. It would have taken too long to cure - the outside looks dry, but the inside remains uncured for quite some time. Thin layers of less than 1/4" thick should cure in about 3 hours each. A heat gun speeds up the curing process, but too much heat will cause a volcanic bubbling effect, ruining the job. Do one mount at a time - you can remove either the front or rear mount without supporting the engine, but I recommend not removing both.

These instructions are for a 1995-1999 FWD Eclipse or Talon. For other vehicles, consult your service manual for proper removal of front and rear roll stops or mounts.

Removing the front mount (easy 5-minute job):
1. Jack up the front (only the front) of the car from the sides.
2. Loosen (but don't remove) the bolt going through the center of the motor mount
3. Evenly loosen and remove the 2 bolts holding the front motor mount to the center member.
4. At this point, the mount should not be supporting any weight - you may want to check if there is a gap between the mount and the centermember with a piece of paper. If not, you may need another jack to push the engine up slightly before removing the bolt through the center but this was not necessary with my car.
5. Remove the bolt going through the center of the mount, and you're done.
6. To reinstall, reverse the process: Put the bolt through the mount, evenly bolt the mount to the centermember, and properly torque everything according to the service manual.

Removing the rear mount: This is much more difficult, because the bolts are hard to get to. This will go more easily with two people, especially when working the center bolt, but it can be done with one person.
1. Take out the battery and tray.
2. Put the car up on 4 stands.
3. Loosen the center bolt going through the mount.
4. Evenly loosen the three bolts holding the base of the mount to the frame. A long extention will be necessary to get the passenger side bolt from above. The two driver side bolts are loosened from under the car.
5. Remove the center bolt.
6. Remove the mount from the car - this is tricky. I found it necessary to loosen the fuel filter bracket to push the filter out of the way. Rotate the base of the mount up, and then work it out through the top by pushing hoses and wires out of the way.
7. To reinstall, reverse the process.


Results:
After modifying just the front mount, the front end was more reluctant to start hopping. The hop was less severe, but still worse than what most people will ever experience. The car was more drivable, but marginally so. I noticed no increase in vibration with just the front mount filled. Engine movement was also reduced.

After this, I installed Ground Control coilovers with Tokicos and 500/300 lb. Eibach springs. This helped a little, but the main cause of the hop was still the engine flopping around in the engine bay.

Then I finally had the chance to fill the rear motor mount. Major difference! Wheel hop is history. If I launch TOO hard, I can purposefully generate some hop, but it is very mild by comparison. Securing the engine to the frame made more of a difference than I ever imagined.

The car simply feels more solid now - the way it should, and without excess vibration. The movement of the engine is something you don't really notice until it's gone. Wheel hop or not, this is a good modification.

Results:
After modifying just the front mount, the front end was more reluctant to start hopping. The hop was less severe, but still worse than what most people will ever experience. The car was more drivable, but marginally so. I noticed no increase in vibration with just the front mount filled. Engine movement was also reduced.

After this, I installed Ground Control coilovers with Tokicos and 500/300 lb. Eibach springs. This helped a little, but the main cause of the hop was still the engine flopping around in the engine bay.

Then I finally had the chance to fill the rear motor mount. Major difference! Wheel hop is history. If I launch TOO hard, I can purposefully generate some hop, but it is very mild by comparison. Securing the engine to the frame made more of a difference than I ever imagined.

The car simply feels more solid now - the way it should, and without excess vibration. The movement of the engine is something you don't really notice until it's gone. Wheel hop or not, this is a good modification.