Our ’73 Plymouth Cuda is a blast to drive but we of course can’t leave well enough alone, there is always something to improve on. That “something” this time around is trying to get our engine to rock & roll a little less in the engine bay. We have always thought the engine moved a lot in this car, but with the new 560-horsepower small block in place, it really torques over pretty aggressively when on the throttle.

Since the car has a pin-on hood it’s very easy to see just how much it moves during a quick rip with the hood off of the car. While chatting with Mopar Connection’s own Kevin Shaw about this, he suggested an old hot rodder’s trick and run a solid motor mount on the driver’s side of the car. It removes the need for a torque strap and still allows for a rubber isolator to soak up any extra vibration. In fear of breaking something as we start to race the car more, we took his advice and began searching for parts.

Above left: View of current motor mount setup in car. Above right: Exploded diagram of saddle type motor mount setup

The car already has DynaTech Engineering’s “MityMounts” installed, which are supposed to be much more durable than factory rubber mounts but we still had a lot of engine movement when on the throttle. Our parts hunt turned up Moroso solid motor mounts (PT# 62520), so we snagged a set from Summit Racing. They come as a pair, so you’ll have an extra for a buddy if you only install one like we’re doing.

The mounts themselves are heavy duty and look well made. They are a bit different than factory style mounts though.

• They do not have a stud protruding from the top side that bolts into the engine block brackets
• They do not have an alignment “hump” on the top side to help align the mount to the engine brackets
• They do not have a nut welded on one ear for you to thread the long bolt into that passes through one side of the mount, the K-member and then threads into the other side of the mount

Above left: Comparison of top side of original motor mount to solid mount. Above right: Comparison of nut on original motor mount to solid mount.

After noticing these three differences, we knew this would be a little bit more involved than just a quick swap. The missing stud on the top of the mount was replaced with a new bolt with a nut and washer on the bottom side. One ½-inch-13 by 1-1/2 inch long flange head bolt, washer and nut would take care of this.

We began disassembly by placing a jack with a 2×6 on top of it to span the bottom of the oil pan and hold the motor in place. We pulled the long 7/16-inch factory bolt out that passes through the motor mount/K-member, and then removed the three nuts and bolts that attach the engine bracket to the engine block. Since the new Moroso mount did not have a nut welded onto it like a factory-style piece, we grabbed a 7/16-inch nut to assemble it back together.

Above left: Comparison of bottom side of motor mounts. Above center: Factory Bolt through Moroso Motor Mount. Above right: Image 7: 5/8” bolt through Moroso Motor Mount.

As we mocked it up on the workbench, we noticed the 7/16-inch bolt was much smaller than the holes in the motor mount. We went to check the K-member next and noticed the same thing – the passage in the K-member was also much larger. How much larger are we talking? Over 1/8 of an inch! You can stick a 5/8-inch bolt through with a little clearance to spare.

We opted to order a shoulder bolt versus using a long 5/8-inch bolt and chance having the threads get hung up while we assembled it all. Using a shoulder bolt and flange nut also resulted in smaller wrench sizes required for the install. McMaster-Carr Shoulder Bolt (PT#91259A807), McMaster-Carr Flange Nut (PT# 9075A50) and a thick 5/8” diameter from the local hardware store worked out great for this setup.

Above left: Engine Bracket attached to solid mount (top side). Above right: Engine Bracket attached to solid mount (bottom side).

Since the new solid mount does not have the alignment “hump” on the top or a stud, we test fit the engine bracket and motor mount and snugged everything up so we could mark where to bolt the two pieces together. The solid mount has a slotted hole so there is a good amount of adjustment possible. Once marked we held the solid mount in the vice and snugged up the 1/2-inch flange head bolt to attach the engine bracket to the mount in the correct position (based on our test fit).

Installing the unit back into the car is a bit more challenging with the 5/8-inch bolt through the motor mount/K-member as there is not much slop in the assembly anymore. First, we reinstalled the three engine bracket bolts but only finger tight. Next, with a little help from a buddy with a 2×4 moving the engine around, or manipulating the jack under the engine to get the long 5/8-inch bolt through the mount and K-member, snug up the nut on the shoulder bolt and three engine bracket bolts and that’s a wrap.

Above left: Shoulder Bolt fitment into solid mount. Above right: Shoulder bolt assembled into solid mount.

Yes, the solid motor mount and larger bolt definitely reduced the movement of the engine. It does translate more vibration through the car though, so the modification may not be for everybody. A possible sweet spot for folks looking for something less aggressive may be upgrading to larger bolts but keeping MityMount engine mounts.

Above: Installation of shoulder bolt into motor mount and K-member

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