Prothane 4-504 Chrysler Polyurethane Motor Mount Insert Spool Kit 1973+

The Prothane 4-504 is a polyurethane spool-style motor mount insert kit designed specifically for small block Mopar, B-Series, and RB-Series engines in Mopar A-Body, B-Body, and E-Body vehicles from 1973 onward. This direct-replacement insert fills the voids in your OEM motor mounts to significantly reduce engine movement and improve power transfer to the drivetrain.

OEM motor mounts are engineered with voids to dampen noise, vibration, and harshness (NVH), but this comes at the cost of engine stability and responsiveness. Over time, stock rubber mounts also deteriorate from heat, oil, and age. Prothane's polyurethane construction resists oil, heat, and age-related degradation far more effectively than rubber, restoring control and precision without requiring a full motor mount replacement.

Key Features:

• Material: High-durometer polyurethane — more durable than OEM rubber, handles intense weight, heat, and pressure
• Spool design: Limits excessive engine rock during acceleration and deceleration
• Application-specific engineering: Not a universal fit — designed precisely for 1973+ Mopar A-Body, B-Body, and E-Body platforms
• Kit includes: 2 motor mount inserts
• Available in Red or Black: Both colors share the same durometer/hardness and performance characteristics; black version includes a small graphite additive that may help reduce squeaking
• Includes Prothane pre-lube for proper installation and squeak prevention
• Lifetime Warranty: Prothane guarantees all parts to be free of defects in materials and workmanship for the life of original ownership

The Prothane 4-504 motor mount insert is an excellent upgrade for classic Mopar performance builds, restorations, and track applications where engine stability and power delivery are priorities. Compatible with Small Block Mopar, B-Series, and RB-Series engines in 1973–1989 A-Body, B-Body, and E-Body vehicles.