Product Description
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:
| Year Range | Engine | Chassis |
|---|---|---|
| 2003–2007 | Ram 5.9L ISB (24V Common-Rail) | Ram 2500/3500 |
| 2007.5–2018 | Ram 6.7L ISB (24V Common-Rail) | Ram 2500/3500 |
Industrial/Off-Highway: ISB4.5, ISB6.7, QSB4.5, QSB6.7 (verify by ESN before ordering).
Compatibility Notes:
- Designed for common-rail ISB/QSB platforms (2003+). For 1998.5–2002 24-valve VP44 and 1994–1998 12-valve engines, these tappets are sometimes used in builds only if the camshaft does not have a mechanical fuel-pump lobe. Always confirm by ESN and cam profile.
- Not for cams using a mechanical lift-pump eccentric.
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.
