Different Types of Motor Mounts
One of the last steps before dropping in a Cummins 4BT or 6BT into an automotive swap is making sure the engine fits snugly in-between the motor mounts. Motor mounts act as both a buffer between the engine and the chassis as well as fastening the motor to the vehicle. Getting the right motor mount can make all of the difference as to how a 4BT or 6BT affects the drive of the vehicle. Older mechanical diesel engines like the 4BT or 6BT will make a fair bit of noise and create vibration within the cab. It is important to select the right type of motor mount for your application and level desired of comfort. This article will describe the various types of motor mounts as well as recommendations for a 4BT or 6BT Swap.
Metal mounts are the most basic type of mounts which are fixed into place with screws, metal clips or simply welded to the frame. Metal motor mounts are mostly found in OE stock vehicles and industrial equipment where vibration isn’t an issue. Metal mounts give the best overall alignment between the engine and the transmission or power take off. The downside to metal mounts is the rigidity of the design. Over time metal mounts can rust, become brittle with freeze/thaw cycles and can be damaged by heavy use and constant vibration.
Rubber mounts are an alternative to the standard metal motor mounts. Rubber mounts are much more flexible and absorb vibrations a whole heck of a lot better than metal mounts. The material allows some flexibility and lateral movement of the engine without disrupting the alignment. Engineering tests show that rubber motor mounts can reduce vibration within the chassis by 39% over traditional metal mounts. The mounts also absorb and muffle sounds waves much better than metal mounts where noise just reverberates. Another benefit of rubber components is they absorb forward momentum when braking as well as when the engine starts up and shuts down. However, rubber mounts are prone to heat and cracking over time.
Liquid mounts are regarded as the best type of mounts you can buy for a Cummins 4BT or 6BT Swap. Liquid mounts, also known as hydraulic mounts, consist of harder rubber, synthetic polyurethane or a silicone pocket infused with a liquid, foam or gel. The malleable material can lessen vibration and noise by over 65% over OE stock mounts. Liquid mounts are the preferred mounts for 4BT and 6BT engines due to their ability to reduce in-cabin vibrations, ease of installation, shock absorption in all directions as well as oil and heat resistance.
Face mounts are a type of mount that directly attaches to the engine and are usually bolted or welded to the block. The weight of the engine is supported by a flange or adapter interface. Many times C-Facing mounts are used to work in conjunction with existing motor mounts for a different type of motor setup. Usually C-Mounts provide excellent vibration control since the engine is essentially attached to the frame instead of floating on the mounts, however the metal design and “one size” fits all can cause some issues installing over existing motor mounts.
Grommet Isolator / Vibration Dampeners
Grommet Isolators are much smaller rubber mounts that are used as secondary mounts to encapsulate the engine. Common locations include corners, side panels and accessory equipment. Isolators act as a buffer between metal surfaces that might cause vibration within the frame or against other engine components.
Some of the most recommended motor mounts for the Cummins 4BT and 6BT are anything from Lord. Their mounts are more expensive than traditional mounting systems but are known for their quality and excellent reduction of vibration. Other recommendations include:
- Anchor 2698 Mounts
- Anchor 2469 Mounts
- Anchor 2859 Mounts
- P-30 Mounts
- Bosch 190 Mounts
- LORD Fulidtastic Mounts
Overall, any of these motor mounts will do exactly as described... hold the motor in place. However, it is our opinion that if you are doing an automotive 4BT or 6BT Swap don't skimp on the motor mounts. Go with the hydraulic mounts to reduce the noise and vibration in the cab. These mounts will reduce the in-cab noise by about 10-30 Db which doesn't seem like a lot but every little bit helps. For the power enthusiast our best recommendation is encapsulating the engine in a 1-2" sound attenuating foam barrier with reflective tape to cover the seams of the chassis. No matter what you choose for your motor mounts you better believe the 4BT and 6BT are tried and true old school mechanical diesels and will behave accordingly... we wouldn't have it any other way.