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Swap Block™ Mock Up Cummins 3.9 4BT Engine Block | GF-EJ-CUMMINS-4BT


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Product Description

  • Engine: Cummins 3.9 4BT
  • Years: 1989-1998
  • Our patent-pending tab-and-slot version of the mock up block provides accurate mounting positions of engine accessories and bolt-ons.
  • Weighs only 26 lbs
  • This unique design is lightweight and comes disassembled for ease of shipping and storage.
  • Precision formed returns on all weight-bearing components and tight tolerance slots create a rigid and accurate representation of the Cummins 4BT 3.9L engine block compared to bolt-together types.
  • One tool accomplishes accurate placement of a 4BT Cummins engine into the chassis build of your choice.
  • Easily positioned by hand, the days of slinging an engine on a crane in and out of your build are over.
  • It's designed to bolt to your transmission while also permitting the attachment of oil pan, motor mounts, header, front timing cover, oil filter housing, and intake.
  • Save time and money and work more safely.
  • Durable steel construction resists heat from welding, so unlike foam blocks, custom motor mounts can be fabricated right on the block.
  • Comes with hardware for exhaust, motor mounts, bellhousing, oil pan, and timing cover.

NOTE: The 4BT was used in commercial vehicles and industrial applications, so some variations to bolt patterns may be seen. 

This video shows how to assemble the LS version of our Swap Block Engine Mock Up Blocks. Assembly with our patent pending tab and slot system is the same for all of our Swap Blocks.

The G Force Patented Transmission Crossmember

Performance Engineered from Start to Finish


Our engineers are also car enthusiasts—which makes designing automotive parts second nature. Because we use our products, we know the importance of crafting them with strength and durability. Get more performance from G Force.

Easy Installation.
It’s Foolproof!

We engineer bold solutions that make installation easier without sacrificing quality. Get more support from G Force.



1989 | 1990 | 1991 | 1992 | 1993 | 1994 | 1995 | 1996 | 1997 | 1998


Cummins: 3.9L 4BT



Weight: 28 lbs

Shipping Dimensions: 24 X 18 X 4 In

Finish: Natural Metal

Mounting Hardware: Included

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