Replacement Hex Head Screw for Cummins ® B/ISB/QSB Applications OEM Cross References: 3901221

1 x?Rocker Lever Support Bolt – 3901221

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Fits?Application:?Cummins 6B /4B Engine

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OE Replacements:?3901221

Application & Fitment

• Engine Make: Cummins
• Engine Model / Application: B/ISB/QSB

Confirm the original part number and engine identification before ordering. Where applicable, also verify serial-number range, production year, piston style, bearing size or other configuration notes shown in the product information.

Part Numbers & Cross References

• OEM Cross Reference: 3901221
• Interstate-McBee Reference: M-3901221

Need Help Confirming Fitment?

Use the engine model, serial number and original part number when checking compatibility. For kits and sets, review the complete component breakdown above before ordering because contents can vary by engine configuration.