Replacing AMC/Rambler inline six motor mounts

23 Apr 2020

Luckily motor mounts only need replacing every ten (or more) years, because it's generally a PITA. They are two metal-rubber-metal sandwiches attached to brackets bolted to the engine block (two bolts) on one face, the other face sits on a saddle or pad on each side of the front suspension cross member (one stud).

The general idea is that you unbolt the motor from the mounts (nothing happens, due to gravity), lift the motor up a couple inches, then wiggle the mount out and replacing each side.

The reality is that often the motor doesn't lift up exactly straight, binding one side, or that you need to lift it up more than a couple inches to get the old mounts out. Then wrestle 600 pounds of motor to line up the four bolts.

The sequence below makes life a bit easier by giving you a lot of (literal) wiggle room without lifting the engine very high. It's not rocket science, I'm not the first to 'discover' this, but I had to figure it out the hard way and so I'm writing it down for posterity.

Lifting the engine

The service manual suggests cutting a piece steel I or U shape to rest on the ledges on either side (where the bolts holding the fender on are located), drilling a hole in the middle of the beam, inserting a long eye bolt into the hole, attaching a short length of chain to the two head bolts with lifting studs, and a wrench on a nut to lift the engine.

I'm lucky enough to have an old portable engine crane, a couple hundred bucks from auto parts stores or Harbor Fright. I bolt a chain across the two lifting headbolt studs and lift that.

Remove the air cleaner, and disconnect the battery to prevent undesireable fireworks, but otherwise leave everything else attached. The rear ("transmission") mount under the tail of the transmission keeps the engine from moving around, since you're only lifting up a couple inches.

Alas I neglected to photograph the lifting process.

The easy way

If you're using a hoist, put the car on jack stands each side so lifting the engine doesn't lift the entire car off the springs. Don't lift yet.

With the engine unlifted remove the four bolts (at least the nuts) and the nuts from the studs.

This is the passenger side/left side mount and it's bracket, in front of the oil filter. (I forgot to photograph it 'before', so astute viewers will see that it's partially unbolted, sorry.)

Lift engine now, approximately 2 inches. The mounts stay sitting on their saddles in the crossmember, the motor lifts off the flat portion of the mounts.

Dont be tempted to wrestle the mount out. I've done that, more than once. I assume everyone has. The stud doesn't really clear the crossmember mount si you are temped to start prying... stop... next step...

Remove the left/passenger side motor mount bracket from the block, three bolts. One of the bolts is difficult to get at with the engine in place, but easy (3/8" drive socket) lifted.

With the bracket out, the left/passenger side mount just lifts out without prying. See all that nice open space? We take advantage of it in the next step.

The drivers (right) side probably won't lift off without assistance, the stud is captured in it's hole. However the bracket removed from the left side allows you to swing the engine to that side, and now the driver's/right side motor mount also just lifts out. I used a jack handle between steering box and alternator; hardly any force is needed.

Here's the drivers/right side location of the mount, just removed.

I clean up everything for jobs like this. This engine had a leaky timing cover and a leaky oil pressure sensor, made a mess and ate the motor mount.


I also write the date on wear parts with a paint pen. I started doing this when I was grumbling about a failed "new" water pump and later realized it was 8 years old.

Drop the new mounts into position on the crossmember saddles, stud in the hole. The left/passenger side is trivial, with all that room.

The drivers/right side I had to pry a bit to make room to drop the stud into the saddle, but easy as before.

Install the left-side bracket, tighten its three coarse-thread bolts now. Then insert the fine-thread bolts, two per mount. One of them threads into the bracket. Install nuts on the small bolts just enough to catch. This is much easier to do while the engine is lifted. Once you drop the motor onto the mounts it is a bear to align the holes for the bolts. The left side is easy with all that room ...

Drop the engine back in place and tighten the four small bolts and the two studs. The Anchor brand motor mount studs had 7/16-NC thread, where the factory used 7/16-NF. Luckily I have a thorough junkbox.

Done!

The passenger side mount was totally rotten, driver side more or less intact. It's good practice to replace split lock washers, these go in the metal scrap box.





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