YHB Solid Motor Engine Mount Combo for Chevy Small Block SBC/BBC — Solid Steel 4-Piece Kit (replaces GM 3990914)

YHB Solid Motor Engine Mount Combo is a four-piece steel replacement set that locks a small block Chevy engine solidly to the chassis to reduce movement and improve driveline consistency in performance and custom builds.

This kit contains two heavy-duty solid motor mounts and two solid steel chassis pads engineered to replace GM rubber-style parts on classic Chevrolet small-block engines. Manufactured from solid steel and sized to match OEM mounting points, the kit targets racers, restomod builders, and anyone installing a high-torque small block where rubber mounts let the engine shift under load. The components are compatible with a range of Chevrolet models and are direct-fit replacements for GM part #3990914 and common chassis mounting pads used across late-model classics.

How do these solid mounts affect engine movement and drivability?

Switching rubber mounts for solid steel reduces lateral and rotational engine motion under throttle and during shifts. That tighter mounting minimizes torque-induced rollback, reduces strain on linkages, and stabilizes accessory alignment—important for precise throttle response and consistent power delivery.

• Eliminates excessive engine movement common with worn rubber mounts
• Prevents torque-related drivetrain binding and linkage misalignment
• Keeps accessories and manifolds aligned for reliable operation

Will these mounts fit my Chevy — what models and specs are covered?

The set fits many classic Chevy platforms using 307, 350, 402, or 454 small-block engines and replaces GM OEM part #3990914 for common SBC installations. Precise dimensions are provided so installers can confirm fitment before purchase.

• Motor mount ear spacing: 2½" inside the ears
• Bolt center dimension from back of mount: 1-11/16"
• Chassis pad centers: 2-5/16" x 5-1/16", center height 2", frame surface to hole center 1"
• Direct-fit replacements for many 1970s–1990s Chevrolet models listed in the product details

How durable and install-friendly are these solid steel mounts?

Made from solid steel, the mounts are built to withstand sustained high loads typical in performance and custom applications. They’re straightforward to install where OEM-style mounts are used, but note that solid mounts transmit more vibration to the chassis than rubber, so expected NVH changes should be considered.

• Solid steel construction for high-load resistance
• Designed to use existing factory bolt locations for a direct swap
• Better for track or custom chassis builds; increases vibration transfer compared to rubber

What exactly comes in the kit and which OEM part does it replace?

The package includes two solid motor mounts and two solid chassis pads—enough for a complete front mounting setup on a small block Chevy. These parts are intended as replacements for GM OEM part #3990914 and common chassis pad applications across several Chevrolet models.

• Includes: 2 solid steel motor mounts + 2 solid steel chassis pads
• Replaces GM OEM part #3990914
• Fits multiple Camaro, Firebird, Chevelle, Malibu, Monte Carlo, El Camino, Nova, Impala, and Caprice years/models

Who is this for? This YHB Solid Motor Engine Mount Combo is aimed at performance enthusiasts, racers, and custom chassis builders who need a no-nonsense, heavy-duty mounting solution for Chevrolet small-block engines. If you’re restoring a classic and want stronger, more predictable engine positioning under load—or building a custom frame where rubber isolation isn’t suitable—this kit provides direct-fit steel mounts with clear dimensions to ensure proper selection and installation.