Moroso 74051 Sealed Battery Box — Black Universal Battery Relocation Box

Sealed Battery Box

The 74051 uses a molded box and lid with an EPDM lid seal.

Moroso supplies approximately four feet of EPDM sealing material that installs into the molded channel around the lid.

Once assembled correctly, the enclosure provides the sealed arrangement required for the intended battery-relocation application.

The lid uses six retaining points around the box.

External Venting

A sealed battery enclosure needs appropriate venting.

Moroso supplies vent tubing with the 74051.

The installation instructions specify routing the vent from the battery box through the vehicle floor so fumes are discharged outside the vehicle.

Moroso specifically warns that the floor opening should be positioned where fumes will not collect beneath the vehicle.

That is an important installation detail.

Sealing a battery inside a box and then giving any gases nowhere to go would defeat a significant part of the enclosure’s purpose.

Battery Hold-Down Included

Battery retention is another major function of the 74051.

Moroso includes a zinc-plated battery hold-down along with:

• 3/8-inch hold-down studs
• Nuts
• Locking nuts
• Flat washers
• Neoprene washers
• Related mounting hardware

The battery is mechanically secured inside the box rather than simply sitting on the trunk floor.

That’s essential in a performance vehicle.

A battery is heavy.

During hard acceleration, braking, cornering or an impact, it wants to keep moving.

Proper battery retention is therefore a safety requirement, not an engine-bay appearance upgrade.

NHRA Battery Retention

Moroso’s installation instructions state that the 74051 is designed to meet NHRA guidelines for battery retention.

Moroso’s current product page additionally identifies the box as approved for racing by:

• NHRA
• IHRA
• SCCA

Always verify the current rulebook for your class before building the vehicle around any specific component.

Sanctioning-body requirements can include more than simply using an approved box.

They may also address:

• Battery mounting
• Hold-down construction
• Master disconnect
• External switch accessibility
• Cable routing
• Venting
• Firewall requirements

The box is one part of the complete installation.

Works With or Without a Rear Firewall

One of the most useful features of the 74051 is Moroso’s explicit positioning for vehicles with or without a rear firewall.

That makes it useful in a broad range of:

• Street cars
• Drag cars
• Road-race cars
• Show cars
• Pro Street builds
• Project cars

A properly sealed and vented battery enclosure becomes particularly important where the battery shares airspace with the passenger compartment.

Follow the installation instructions and applicable regulations for the vehicle.

Compatible Battery Group Sizes

Moroso specifies compatibility with a substantial range of common battery group sizes.

The 74051 is designed to hold:

• Group 21
• Group 24
• Group 26
• Group 34
• Group 42
• Group 54
• Group 55
• Group 56
• Group 61
• Group 62
• Group 63
• Group 85
• Group 86
• Group 96R

That makes the 74051 significantly more useful than a box designed around one proprietary battery.

Top-Post or Side-Post Batteries

Moroso also specifies compatibility with batteries using either:

Top-post terminals

or

Side-post terminals

That gives builders more freedom when choosing the battery itself.

However, terminal style isn’t the only fitment consideration.

The battery still needs to fit within the box dimensions and work correctly with the supplied hold-down arrangement.

Inside Dimensions

Moroso specifies the internal dimensions as:

10-1/2 inches wide

8-1/4 inches deep

8-1/2 inches tall

These are the dimensions customers should use when determining whether a particular battery physically fits inside the enclosure.

Do not use the shipping-package dimensions for battery fitment.

Outside Dimensions

Moroso lists the actual outside dimensions as:

13-1/8 inches wide

11-1/8 inches deep

11-1/8 inches tall

These dimensions are important when determining whether the complete enclosure fits in the proposed trunk location.

Leave additional room for:

• Lid removal
• Battery cables
• Vent tubing
• Master disconnect wiring
• Service access

A battery box that technically fits but requires removing the rear suspension to open the lid isn’t particularly convenient.

Cable Grommets Included

Moroso includes plastic grommets for routing the battery cables through the box.

Its installation procedure instructs the installer to determine where the cables should exit and drill the appropriate openings before installing the grommets.

This helps prevent the cable insulation from rubbing directly against the edge of the battery-box opening.

Cable protection is especially important on a trunk-mounted battery because the positive cable may run nearly the entire length of the vehicle.

Long Battery Cables Need Protection

Rear battery relocation means a long high-current cable.

That cable should be routed carefully.

Avoid:

• Exhaust heat
• Sharp sheet metal
• Driveshafts
• Suspension movement
• Steering components
• Unprotected pass-throughs
• Areas likely to be crushed by a jack or lift

Use proper grommets wherever a cable passes through sheet metal.

Secure the cable so it cannot move against sharp surfaces.

A trunk-mounted battery cable isn’t a place to experiment with the electrical equivalent of “it probably won’t rub through.”

Moroso 74055 Battery Installation Kit

Moroso specifically recommends its 74055 Battery Installation Kit for the 74051.

The 74055 includes:

• 20 feet of 2-gauge battery cable
• Four terminal eyes
• Terminal fittings
• Shrink sleeves
• Cushion clamps
• Plastic grommets
• Additional battery connection hardware

Moroso designed the kit specifically around relocating a battery to the trunk area.

That makes:

74051 + 74055

a very natural Pro Street Online bundle.

Battery Cable Is Not Included With the 74051

This needs to be clear on the product page.

Moroso states that battery cable is not included with the 74051.

Customers relocating a battery will need a suitable cable kit separately.

Moroso recommends the 74055.

That’s an excellent cross-sell because someone purchasing the box for a fresh relocation project will almost certainly need the electrical hardware as well.

Pair With the Moroso 74101 Battery Disconnect

The 74051 also pairs directly with the Moroso 74101 Heavy-Duty Battery Disconnect Switch.

Moroso’s 74051 installation instructions specifically state that a battery disconnect switch is required for racing and reference Moroso disconnect switches including the 74101.

That gives you a strong three-product ecommerce cluster:

74051 — sealed battery box

74055 — rear battery installation/cable kit

74101 — heavy-duty master battery disconnect

Those products solve three separate parts of the same relocation project.

Typical Rear Battery Layout

A properly engineered race-car installation might look like:

BATTERY

↓

MOROSO 74051 SEALED BOX

↓

BATTERY CABLE

↓

MOROSO 74101 MASTER DISCONNECT

↓

MAIN POSITIVE CABLE

↓

STARTER / POWER DISTRIBUTION

The alternator circuit then needs to be incorporated correctly so operating the master switch produces the required shutdown behavior.

That’s particularly important on race cars.

Master Disconnect Requirements

Moroso’s instructions explicitly note that a battery disconnect is required for racing applications.

Depending on the racing organization, the switch may need to be externally accessible.

For drag-racing applications, a master disconnect is commonly located at the rear of the vehicle.

The exact installation must follow the current rules for the vehicle and class.

The Moroso 74105 Push/Pull Battery Disconnect Kit can also be used with compatible switches when a remote external actuator is required.

Alternator Wiring Matters

Relocating the battery doesn’t eliminate the alternator as an electrical power source.

On an alternator-equipped race car, the master cutoff system must be wired so operating the required emergency disconnect actually shuts the vehicle down.

That may require:

• Correct alternator output routing
• An alternator shutdown relay
• A multi-pole battery/alternator disconnect
• Application-specific wiring

Don’t assume placing a switch in the battery cable automatically guarantees complete engine shutdown.

Test the system.

Rear Battery Relocation and Voltage Drop

Moving the battery to the trunk substantially increases cable length.

Cable resistance increases with length.

That makes conductor size and connection quality important.

Excessive voltage drop can cause:

• Slow cranking
• Starter solenoid clicking
• ECU resets during starting
• Hard starting
• Charging problems
• Hot terminals

Moroso’s 74055 relocation kit uses 2-gauge cable.

Other combinations may require different cable sizing depending on current, cable length and electrical architecture.

Grounding Matters Too

The positive cable gets most of the attention during a battery relocation, but the ground circuit is equally important.

The starter circuit must have a low-resistance return path to the battery.

Depending on vehicle construction and electrical design, this may involve:

• Battery-to-chassis ground
• Engine-to-chassis ground
• Dedicated engine ground
• Additional bonding straps

Paint, powder coating, corrosion and loose fasteners can all increase resistance.

A beautiful battery relocation with a terrible ground is still a terrible electrical system.

Perform a Voltage-Drop Test

After completing the relocation, test the starting circuit under load.

A voltage-drop test can identify excessive resistance in:

• Battery cables
• Ground cables
• Master disconnect
• Cable terminals
• Chassis grounds
• Starter connections

This is much more useful than simply measuring battery voltage with the engine turned off.

High-current problems often appear only when the starter is actually drawing current.

Secure the Box to Structure

The battery box needs to be securely attached to the vehicle.

Moroso’s instructions call for drilling through the battery box and mounting area for the supplied hold-down studs.

Before drilling, Moroso specifically warns installers to check underneath the proposed mounting location for obstructions such as the fuel tank.

That warning deserves emphasis.

Before drilling through a trunk floor, verify what is underneath it.

Fuel tanks, fuel lines, brake lines and wiring harnesses tend to react poorly to surprise drill bits.

Use the Hold-Down Correctly

Moroso instructs installers to center the supplied hold-down in the box before drilling the mounting holes.

The hold-down studs pass through the box and floor pan, with locking hardware securing them underneath.

The battery is then secured with the upper hold-down.

Moroso’s instructions also specify removable thread-locking compound on the appropriate hold-down fasteners.

Follow the supplied installation instructions rather than improvising the retention system.

Vent the Box Outside the Vehicle

Moroso includes vent tubing and large grommets for external ventilation.

The installation calls for a vent opening through the box and another through the vehicle floor.

The vent outlet should terminate where fumes cannot collect underneath the vehicle.

This is especially important in vehicles without a sealed rear firewall.

Useful for Engine-Bay Packaging

Rear battery relocation isn’t always performed purely for weight transfer.

Modern performance builds can consume enormous amounts of engine-bay space.

Moving the battery can make room for:

• Turbocharger plumbing
• Supercharger hardware
• Intercooler reservoirs
• Coolant tanks
• Air intake systems
• Dry-sump tanks
• Electronics

Moroso itself specifies the 74051 when relocating the battery to make room for certain Mustang supercharger coolant tanks.

Universal Fitment

The Moroso 74051 should be classified as:

Universal / battery-size specific

It is not a conventional year/make/model component.

Compatibility depends on:

• Battery dimensions
• Battery group size
• Available mounting space
• Vehicle construction
• Racing rules
• Cable routing
• Vent routing

For Pro Street Online, avoid assigning misleading vehicle-specific fitment simply because the box can be installed in many cars.

Supplied Package Dimensions

Your distributor data lists:

Package Height: 26.924 cm / approximately 10.6 inches

Package Length: 36.068 cm / approximately 14.2 inches

Package Width: 31.496 cm / approximately 12.4 inches

Package Weight: 6.3 pounds

These are shipping dimensions.

For actual installation planning, use Moroso’s published box dimensions.

Moroso 74051 Specifications

Part Number: 74051

Product: Sealed Battery Box

Color: Black

Fitment: Universal / battery-size specific

Outside Dimensions: 13-1/8″ W × 11-1/8″ D × 11-1/8″ H

Inside Dimensions: 10-1/2″ W × 8-1/4″ D × 8-1/2″ H

Battery Terminal Compatibility: Top post or side post

Battery Group Compatibility: 21, 24, 26, 34, 42, 54, 55, 56, 61, 62, 63, 85, 86 and 96R

Racing Approval: Moroso lists NHRA, IHRA and SCCA approval

Included: Battery box, molded lid, battery hold-down, hold-down studs, nuts, washers, grommets, EPDM lid seal, vent tubing and installation hardware

Battery Cable: Not included

Recommended Cable Kit: Moroso 74055

Recommended Master Disconnect: Appropriate Moroso disconnect such as 74101, depending on the electrical system and racing requirements

Package Weight: 6.3 lb, according to supplied distributor data

Who Should Buy the Moroso 74051?

The Moroso 74051 is an excellent choice for builders relocating a conventional automotive battery to the rear of:

• Drag cars
• Street/strip cars
• Pro Street builds
• Muscle cars
• Hot rods
• Road-race cars
• Show cars
• Project cars

It’s particularly useful where a sealed, externally vented enclosure is required or desirable.

Who Should Verify Fitment First?

Measure carefully if you’re using:

• Oversized batteries
• Unusual AGM cases
• Lithium racing batteries
• Custom battery terminals
• Batteries with integrated electronics
• Nonstandard battery hold-down arrangements

Use the 10-1/2 × 8-1/4 × 8-1/2-inch internal dimensions rather than relying solely on a battery group number.

Physical measurement wins.

Final Verdict

The Moroso 74051 Sealed Battery Box is a complete solution for relocating a conventional automotive battery to the rear of a street, race or show car.

Its sealed lid, external venting provisions, positive battery retention and included mounting hardware address the important parts of a proper relocation instead of simply giving the battery a plastic place to sit.

Moroso also publishes specific compatibility with numerous common battery groups and lists the box as approved by NHRA, IHRA and SCCA.

Pair it with the 74055 Battery Installation Kit and the 74101 Heavy-Duty Battery Disconnect you just added and you have a logical battery-relocation package instead of three unrelated products buried in separate catalog categories.

And before drilling the trunk floor, look underneath it.

A perfectly centered battery box is considerably less impressive when the second mounting hole goes through the fuel tank.