You don’t need a $300 metal fixture to get accurate big-end and small-end rod weights. DIY engine builders usually rely on one of two proven techniques:

1. A 3D-printed balancing jig (most accurate, easiest, fastest)

2. The chain/suspension method (low-cost frictionless method, requires perfect leveling)

Both methods work extremely well when done correctly.

For the full end-weight workflow, see the Complete Connecting Rod Balancing Guide.

Method 1: 3D-Printed Rod Balancing Jig (Most Accurate & Easiest)

This is the preferred modern method for DIY engine builders.

A well-designed 3D-printed fixture:

• Holds the rod at a consistent, repeatable height

• Keeps the rod perfectly level every time

• Eliminates friction

• Prevents scratches or damage

• Works with any digital scale

• Replicates the geometry of expensive metal rod fixtures

If you want a ready-to-print design, the 3D-Printed Connecting Rod Balancing Jig is optimized specifically for rod end balancing.

What You Need

• Digital scale (0.1 g or 0.01 g recommended)

• Printed jig

• Flat, level table

How to Use It

1. Support the small end in the jig

2. Place the big end on the scale

3. Record the big-end weight

4. Swap orientation

5. Support the big end in the jig

6. Place the small end on the scale

7. Record the small-end weight

Because the jig fixes geometry, your readings will be repeatable to ±0.1 g with a good scale.

Pros

• Best accuracy

• Fast, repeatable, and simple

• No technique required

• Works for performance and race engines

Cons

• Requires 3D printing (or buying pre-printed)

Method 2: Chain/Suspension Method (Frictionless DIY Alternative) — MUST Be Perfectly Horizontal

This is a clever, low-tech method that works shockingly well if the rod is positioned perfectly horizontal. If it is even slightly angled, the reading will be wrong.

The idea is simple:

• One end of the rod is suspended freely using a thin string, wire, or chain

• The other end is placed on a scale

• The suspended end supports its own weight

• The scale reads only the isolated end weight

This nearly eliminates friction—but only if the rod is absolutely level.

What You Need

• Digital scale

• A rigid stand, hook, shelf bracket, or tripod

• Very thin string, fishing line, or chain

• A straight pin/rod to pass through the rod bore

• A bubble level (optional but recommended)

How to Ensure Accuracy

All of the following must be true:

• The rod must be perfectly horizontal

• The suspended end must hang completely free (no touching anything)

• The string must pass through the bore, not wrap around the rod
  

• There must be no sway before recording a measurement

How to Check Horizontal Level

Use a mini bubble level placed on the rod beam, then adjust:

• The height of the hook/suspension point

• Or add thin shims under the scale

Adjust until the rod beam is perfectly level.

How to Measure Big-End Weight

1. Pass a pin through the small-end bore

2. Suspend the small end on the string

3. Level the rod horizontally

4. Place the big end on the scale

5. Let the rod settle

6. Record the reading

How to Measure Small-End Weight

1. Pass the pin through the big-end bore

2. Suspend the big end

3. Level the rod

4. Place the small end on the scale

5. Let it settle

6. Record the reading

Pros

• Almost zero friction

• Very cheap

• Surprisingly accurate when level

Cons

• Rod MUST be perfectly horizontal

• Setup takes time

• Slight sway delays readings

• Harder to get consistent back-to-back measurements

Safe Material Removal (Applies to Both Methods)

Remove small amounts of material ONLY from:

Big End

• The exterior of the connecting-rod bolt bores, evenly

Small End

• The exterior of the wrist-pin bore, evenly

Never remove material from:

• Beam

• Wrist-pin bore or bushing

• Big-end bore

• Bearing tang areas

Evenness is more important than the amount removed.

Which Method Should You Use?

Use the 3D-Printed Jig if you want:

• Highest accuracy

• Fastest workflow

• Repeatable results

• Race-engine-level tolerances

Use the Chain Method if you want:

• Zero-cost solution

• Good accuracy with patience

• A temporary or backup method

Most builders try the chain method once…and quickly switch to a jig because of the speed and repeatability.

For the easiest, most consistent solution, the 3D-Printed Connecting Rod Balancing Jig gives professional-level results at a fraction of the cost.