Cummins 3947759 — Genuine Valve Tappet (Lifter) for ISB 5.9L & 6.7L

MPN: 3947759  |  Also Known As: valve lifter, tappet, cam follower  |  Supersedes: 4891226

Genuine Cummins valve tappet engineered for precise valve-train control on ISB common-rail platforms. Sold individually; 12 required per engine. Ideal for stock refreshes, camshaft replacements, or preventative service when lifter wear is present.

Features & Benefits

• OE geometry & metallurgy for quiet operation and long service life.
• Direct-fit drop-in with OEM surface hardening to protect cam lobes.
• 1.50" outside diameter common-rail style tappet for ISB applications.
• Sold individually to match the exact quantity you need (12 per engine).
• Backed by Cummins quality for fit, function, and durability.

Verified Fitment (Automotive)

Automotive drop-in:

Industrial/Off-Highway: ISB4.5, ISB6.7, QSB4.5, QSB6.7 (verify by ESN before ordering).

Specifications

• Type: Flat tappet (valve lifter), cam follower
• Outside Diameter: 1.50 in
• Quantity Required: 12 per engine (sold individually)
• OE Part Number: 3947759 (replaces 4891226)
• Cross-References (for identification): PAI 191859

What’s In The Box

• (1) Genuine Cummins Valve Tappet (3947759)

Installation Tips

• Inspect cam lobes for scuffing/pitting; replace cam if excessive wear is present.
• Pre-lube tappet faces and cam lobes during assembly.
• Best practice: replace all 12 tappets together to ensure even break-in.
• Set valve lash to factory spec after reassembly and again after initial heat cycle.
• Follow Cummins service procedures; verify by Engine Serial Number (ESN).

FAQ

How many tappets do I need?

There are 12 tappets on the ISB 5.9L/6.7L. This part is sold individually—order quantity 12 for a full set.

Will this fit my 1998.5–2002 24-valve?

It’s designed for 2003+ common-rail ISB. Some builders use it on earlier engines only when the camshaft lacks a mechanical fuel-pump lobe. Verify by ESN and cam profile before ordering.

Does this replace 4891226?

Yes—3947759 supersedes Cummins part 4891226.

Is this an OEM Cummins part?

Yes, this is a genuine Cummins valve tappet with OEM geometry and hardening.

Should I replace the camshaft, too?

If any lobe shows measurable wear/scoring, replace the camshaft and all tappets together to prevent rapid failure.

Do I need new pushrods?

Stock-length pushrods are used with these tappets. Replace pushrods if bent, worn, or when upgrading valve-train components.