What size harmonic balancer for Chevy 350?
The Chevy 350 typically uses a 6.75-inch outer-diameter harmonic balancer. The exact size you need depends on the engine’s crank balance and the timing cover assembly, so verify by checking the existing damper or the engine build sheet.
Rebuilding or replacing a Chevy 350 raises a common question about balancer size. While 6.75" is the standard starting point for many small-block Chevys, some builds require a larger damper due to crank balance weights or specific performance aims. The following guide explains the two main sizes you’ll encounter and how to determine the right one for your engine.
Two common sizes you will encounter
Most Chevy 350s fall into one of two outer-diameter damper categories. The choice hinges on the crank balance and the accompanying flywheel/flexplate, so picking the right size is about matching the entire rotating assembly.
- 6-3/4 inch (6.75") harmonic balancer: This is the most widely used size on many factory and aftermarket small-block Chevys.
- 7-1/4 inch (7.25") harmonic balancer: This larger size is seen on some older or heavier-duty external‑balance setups and certain performance builds.
Note that there are rare exceptions based on specific balance weights or timing cover designs. Always confirm by matching to the crank’s balance spec or by referencing the engine’s build sheet.
How to determine your correct balancer
To avoid installing an incorrect balancer, follow a precise verification process before ordering parts.
- Identify the engine’s balance type and weight (external vs internal balance) from the crankshaft part number or the vehicle’s service manual.
- Measure the outer diameter of the existing balancer with a ruler or caliper to confirm its size, if you’re replacing a removed unit.
- Check the flywheel or flexplate weight and the timing cover compatibility to ensure the damper will align correctly with the pulleys and belt system.
- Consult a Chevrolet parts catalog or a qualified machine shop with your engine code, year, and model to obtain the exact part number needed.
By confirming balance type and exact diameter, you’ll ensure proper belt alignment, timing marks, and overall engine reliability when the engine starts up again.
Buying tips and compatibility
Choosing the right balancer involves more than just diameter. Compatibility with your crank and accessories is essential for reliable operation.
Know your engine’s balance weight
On a Chevy 350, the proper balancer weight must match the crank’s balance (external or internal). If you mismatch weights or diameters, you risk vibration, belt wear, or damage to the crank and bearings.
- Match the balancer to the crank and to the flywheel/flexplate your build uses.
- Ensure the timing marks line up with your ignition setup after installation.
- Choose a reputable brand and verify that the part number corresponds to your engine’s year and model.
Careful selection now saves headaches later: incorrect balance or diameter can lead to poor timing, belt misalignment, or premature wear on rotating components.
Bottom line
For most Chevy 350 builds, start with a 6.75-inch harmonic balancer and verify it against your crank’s balance and the accompanying flywheel or flexplate. If your engine’s balance weight or timing cover calls for it, a 7.25-inch damper may be appropriate. When in doubt, consult the engine’s documentation or a qualified technician to confirm the exact part number and diameter.
Summary: The Chevy 350 commonly uses a 6.75" harmonic balancer, but the correct size depends on the crank balance and accompanying components. Verify by checking the existing damper, engine build sheet, or with a professional to ensure proper fitment and reliable operation. This approach helps prevent misalignment, vibration, and component damage.
Can I use a 305 harmonic balancer on a 350?
A 305 balancer and a 350 balancer have different timing locations, the 305 tab is straight up (12 o'clock position) 350 is at 2 o clock. The balancers are interchangeable since they are zero balanced.
What is the diameter of the harmonic balancer on a small block Chevy?
JEGS Harmonic Balancer | Fits Small Block Chevy | 6.75” Diameter | Internal Balance | Exceeds OE Specifications.
Does it matter what size harmonic balancer I use?
No matter what anybody tells you, size does matter when it comes to the harmonic balancer you use on an engine. Putting an incorrectly-sized balancer on an engine will do more than just cause it to not reach its full performance potential … it will cause serious damage to the rotating assembly.
What size balancer is on a 350 Chevy?
8-inch
Nearly all 350s came with an 8-inch balancer because of their relatively long stroke.
