Replacing engine mounts

[MW79]

Hi,

I have been told that my engine mounts need replacement.

Will this reduce vibration from the engine?

I have not researched how to do this yet. Presumably it will involve taking the weight of the engine on a lift and then replacing the mounts. Are there any unexpected pitfalls to avoid or any useful tips?

[vito]

Hi,

I have been told that my engine mounts need replacement.

Will this reduce vibration from the engine? If you go with the harder mounts then it will transmit more.

I have not researched how to do this yet. Presumably it will involve taking the weight of the engine on a lift and then replacing the mounts. Yup

Are there any unexpected pitfalls to avoid or any useful tips? Practice Yoga. Look at the bolt that holds the two mounts together. If the pass side bolt was put in from the front, you will have a swell time getting it out

Just remember that the corvettes have their engines/transmission installed at an angle. I would measure the side to side distance of the installed mount before you order and confirm that the new ones are the same width.

[MW79]

Just as well to replace transmission mounts at the same time?

[MaineVette]

I'd replace both engine mounts and the tranny mount at the same time. It shouldn't be too hard. You may need to remove your manifolds/headers and a few other items to gain access though. It's tight quarters.

You can use an engine hoist to lift the motor just a small bit. That should allow you to get the old ones unbolted so you can slide them out.

I don't think replacing the mounts will reduce vibration though. If you have excessive amounts of vibration you probably have something out of balance

Good luck!

[MW79]

The thought about vibration came from having had the engine mounts on the family hatchback recently replaced. Vibration when pulling away had become noticeable and new engine mounts fixed it.

The Corvette is similar when pulling away.

I might try using jacks under the engine to avoid sourcing an engine hoist. Not sure if this is a good idea.

[rbryce1]

I read in the past an article that discussed problems with GM motor mounts, and that resulted in a very large recall.

The mounts were breaking due to over torquing the mount. When this happened, the engine on the drivers side lifted up in the air enough to 1) bind up the throttle linkage and not allow the carburator to stop feeding fuel to the engine and 2) in the case of automatic transmissions, would actually cause the transmission shift linkage to permanently shift one slot, resulting in Park being Reverse. This was bad!

The fix was the redesigned motor mount that is called the locking motor mount.

Here is a photo of the standard mount (actually, it is shown upside down).



It has 3 bolts that fasten it to the engine block and one bolt that passes throughthe mount, then through the frame, then back through the mount which links the engine to the frame. If the rubber breaks, nothing is there to prevent the engine from lifting up in the air.

Here is a photo of the locking mount (again, shown upside down).



Note the T shaped pawl on the far side of the mount. It is molded to the part of the mount that is bolted to the engine block. Remembering the mount is being shown upside down, if the rubber breaks, the engine can only rise up about 3/8" before the pawl stops it from rising any farther by hitting the remaining part of the mount that is fastened to the frame.


On a side note, during the recall, GM never replaced all the existing mounts with the locking mount, it wrapped a small cable around the exhaust manifold and attached it to the bolt that linked the motor mount to the frame. Why? Beause the cable cost $1.00 and the mount cost $20.00!

Another side note, this modification was not done on Corvette, as there were no instances reported of the throttle linkages binding up, maybe due to the design of the Corvette linkage. I would still consider installing this mount if it is available. It's about $10.00 more than the origional design.

[vito]

Interesting Bob,

I remember the mounts from the 60's having a finger in the middle to help if the mount split.

[MW79]

I shall probably end up using the jib type engine hoist with the two legs that are positioned under the vehicle.

Will i be able to position the hoist to one side or will it have to go at the front (requiring removal of hood)

[vito]

Probably have to remove a wheel. Support the car with some big pieces of wood.

[rbryce1]

When I did mine, I just put a floor jack under the Bell Housing and lifted the engine about 1/2", just enough to take the weight off the motor mount. Of course, I have a 1/4" thick steel Lakewood Scattershield Bell Housing, not the stock aluminum one.