Solid motor/trans mounts

#1

Who uses solid motor/trans mounts? Seen any problems with them? Usually use AKG poly stuff, think of going to solid.

#2

Many use solid and to my knowledge with no issues. I use Delrin plastic mounts which are very solid on both engine and tranny.

#3

I’m not a fan of solid mounts because they simply aren’t needed. Delrin or hard poly is more than strong enough to handle the torque our engines produce without appreciable deflection. At the same time, the delrin/poly dampens some of the engine vibration. Solid metallic mounts transmit more of the engine vibration to the car and create harmonics that could damage your engine over the long term. I’ve recently seen a picture of BMW S52 engine where the oil pickup tube fatigued and shatter after an endurance race when using solid mounts. Our engines are not S52s, but why take the risk for zero performance gain. On the other hand, some folks have had poly mounts melt. I have personally not had this issue; heat shields should mitigate the melting risk.

#4

I wrote the rule change request re. solid motor mounts. The reasoning was failed passenger side motormounts, not any performance advantage. Like Rich said, the heatshield should be good enough to protect the mount. But it’s not always good enough. When one of our mounts fail, it’s always on the passenger side, whether or not their’s a heatshield.

This is a big deal on cars with old style cooling systems. The radiator return hose runs close to the alternator fan. If the engine moves around a bit the fan will cut the hose. The year I wrote the rule change request 3 people lost engines due to this.

That said, I don’t use a metal motor mount. Just because IMO the ruleset ought to allow it, doesn’t mean I thought it was worth doing on my own car. If I was going to do it, I might be tempted to do it only on the passenger side.

#5

We have had our engine move far enough forward with poly mounts to ding the radiator so we always use solid motor mounts but always a poly transmission mount to eliminate some of the harmonics.

Heat would be an issue for delrin and/or poly.

#6

If you have a saw and a drill you can make cheap motor mounts. Just order the correct diameter of uhmw-pe or acetal. I did this after my IE poly mount failed on the passenger side.

#7

The hard poly mounts from AKG work great. The reason you want hard/solid is so the torque is applied directly to the drive shaft and not wasted in trying to twist the motor. If you drive the car back to back with the different bushings, you will see a considerable difference in response.