Motor mount inserts are polyurethane pieces that fit into the voids or shell of an existing engine mount, firming it up and replacing worn rubber without removing the whole mount. They reduce engine movement, cut the thump when shifting and resist heat and oil. On applicable platforms our engine mount inserts install in under an hour. 

Replacing a complete engine mount means supporting the engine, unbolting brackets and sometimes removing other parts to reach it. Motor mount inserts offer a quicker route on many vehicles. They are popular with diesel truck owners, V8 drivers and anyone whose rubber mounts keep tearing. Here is how they work, when they suit your vehicle and how they fit into our range of engine mount bushings.

Why LS Swaps Need Different Motor Mounts 

LS engines use a different block mounting pattern from the older small block engines many classic chassis were designed around. The factory mount brackets on your frame were built for the original engine, so the LS will not bolt straight in. Something has to bridge the gap between the LS block and the chassis mounting points. 

Engine position matters just as much as bolt pattern. Move the engine too far forward and it may hit the radiator or crossmember, too low and the oil pan hangs below the frame, too far back and the headers foul the steering or firewall. LS engine mounts set the engine's height, fore and aft position and angle in one go. 

Many factory engine mounts are built with voids, gaps molded into the rubber that make the mount softer and quieter. Those voids also let the engine move further under torque, and the thin rubber around them is often where cracks and tears start. A motor mount insert fills those voids with polyurethane, or replaces the worn cushion inside the mount's metal shell. 

The result is a mount that resists engine movement much more firmly while still cushioning vibration. The original brackets and shell stay on the vehicle, so the factory mounting points and engine position are retained.

 
LS-Series Motor Conversion SetLS-Series Motor Conversion Set

LS-Series Motor Conversion Set

The Main Types of LS Swap Motor Mounts

Insert type 

Where it fits 

Typical use 

Motor mount insert bushings 

Into the voids of existing engine mounts 

Passenger and performance platforms 

Diesel motor mount inserts 

Diesel engine mounts, including clamshell designs 

High-torque diesel trucks 

Front and rear motor mount inserts 

Specific front or rear mount positions 

Platforms with separate front and rear mounts 

Engine mount rear insert bushings 

The rear mount shell, without full mount removal 

Applicable performance and passenger vehicles 

Four-mount insert sets 

Every mount position on the vehicle 

Complete renewal in one kit 

Manual transmission mount inserts 

Transmission mount on manual gearbox models 

Reducing shift-related drivetrain movement 

Torque arm insert bushings 

Engine torque arms and struts 

Controlling engine rock 

Whatever you choose, plan the oil pan, headers and accessory drive at the same time. These parts all interact with engine position, and changing one can force changes to the others. 

Engine Position and Clearance Checks 

Before you finalize your LS motor mounts, mock up the engine and check these points:

  • Oil pan clearance: Make sure the pan clears the crossmember, steering linkage and ground with suspension movement.
  • Header clearance: Check the steering shaft, frame rails and starter for room.
  • Hood clearance: Measure from the intake manifold to the underside of the hood.
  • Radiator and fan: Allow space for the cooling system ahead of the accessory drive.
  • Driveline angle: Set the engine and transmission angle so the driveshaft operates within a sensible range.
  • Transmission crossmember: Confirm the transmission mount lines up with the new engine position. 

Taking time here saves cutting and rework later. Many builders bolt the engine in with the mounts loosely fitted, check every clearance and only then tighten everything down. 

Why Polyurethane Suits LS Swap Engine Mounts 

An LS produces strong torque, and many swaps add more power with cam, intake and forced induction upgrades. Rubber mounts that were designed for a milder engine often tear under that load, letting the engine rock, thump on launch and lift on one side. Excessive engine movement can also strain exhaust connections, wiring and throttle linkages. 

Polyurethane resists torque reaction, heat and oil far better than rubber, so it holds the LS steady through hard launches and shifts. Our range includes a V8 LS1 motor mount and an LS-series motor conversion set, alongside other V8 motor mount sets and complete engine and transmission mount sets. Check fitment for your chassis and engine combination before ordering, and our support team can help confirm the right parts. 

For a deeper look at materials, read our comparison of polyurethane vs rubber motor mounts. If you want to understand how mounts are arranged across a rear-wheel drive layout, see our guide to how many motor mounts a car has. 

Do Not Forget the Transmission Mount 

An LS swap often brings a different transmission too, such as a modern automatic or a six-speed manual. That changes the transmission mount location and may need a modified or new crossmember. Match the transmission mount to the same firmness as your engine mounts so the drivetrain moves as a unit rather than twisting between them.

 

FAQs

Looking for more information about LS swap motor mounts? Below we answer the most commonly asked questions

Can I use my old small block motor mounts for an LS swap?

Not directly, because the LS block uses a different bolt pattern. Adapter plates let you use mounts designed for the original engine, or you can fit swap-specific LS motor mounts.

What are the best LS swap motor mounts?

The best choice depends on your chassis, oil pan, headers and power level. Swap-specific mounts or complete conversion sets give a known engine position, and polyurethane cushions handle LS torque well.

Do LS engine mounts affect engine position?

Yes, the mounts set the engine's height, fore and aft position and angle. That position decides oil pan, header, hood and driveline clearance.

Are polyurethane motor mounts good for an LS swap?

Yes, polyurethane resists the torque, heat and oil that tear rubber mounts. It keeps the engine steady through launches and shifts on high-powered builds.

Do I need a new transmission mount for an LS swap?

Often, yes, especially if the swap includes a different transmission. The mount and crossmember need to match the new engine position and transmission.

How do I check driveline angle after an LS swap?

Measure the engine, transmission and pinion angles with an angle finder once the engine is mounted. Adjust the mounts or transmission crossmember to keep the angles within a sensible range.

Build your LS swap on mounts that can handle the power. Explore our engine mount bushings, including our LS1 motor mount and LS-series conversion set.