Home/All Cylinder Head Parts/3991773 Cummins ISB 5.9L 24-Valve Loaded Cylinder Head – New, Stage 1
4983298 Cummins ISB 6.7 2013+ loaded cylinder head - new, JAK's Diesel
Cummins · Models: ISB / ISB 5.9 / 6B 5.9

3991773 Cummins ISB 5.9L 24-Valve Loaded Cylinder Head – New, Stage 1

Commercial diesel cylinder head. Match the listed part and engine identifiers before ordering.
Warranty DetailsJAK's DieselMay Qualify for Free Freight
$1,899.00
In Stock
Fitment details

Want us to check the fit? Share any details you have below. All fields are optional. Your request will be included with your order, and a specialist may contact you before fulfillment.

Secure Checkout Review Return Policy Warranty Details May Qualify for Free Freight
JAK'S Part #JAKS-3991773
Not sure it's the right fit? Call a specialist
(720) 445-6249
Talk to a tech or text a photo of your part tag — we'll confirm fitment before you buy
3991773 Cummins ISB 5.9L 24-Valve Loaded Cylinder Head – New, Stage 1
BrandJAK's Diesel
Part CategoryCylinder Heads
Engine MakeCummins
Engine ModelISB · ISB 5.9 · 6B 5.9
ConditionNew
Stage / TierStage 1

New, fully loaded cylinder head for the Cummins ISB 5.9L 24-valve, built to replace Cummins 3991773 (also 3943627). Standard intake and exhaust valves for a straight stock-power replacement. It arrives assembled and ready to bolt on, with no core to send back.

What's Included

  • New cylinder head casting
  • New intake and exhaust valves (Stage 1 standard intake and exhaust)
  • New valve springs, retainers and keepers
  • Valve guides and valve stem seals installed

Not included: head gasket set, head bolts, injectors, rocker assemblies. Ask us and we will quote the matching gasket set and bolt kit.

Specifications

Replaces Cummins 3991773, 3943627 and cross-references below
Engine Cummins ISB 5.9L 24-valve
Condition New — no core
Assembly Loaded (valves, springs, retainers, keepers, guides, seals)
Valve package Stage 1 — standard intake and exhaust
Brand JAK's Diesel

Fitment

Fits Cummins ISB 5.9L 24-valve engines that use the 3991773 head. Mechanical-injection and common-rail 5.9 heads differ, so we verify by ESN before shipping. For the 6.7, see our ISB 6.7 head. We confirm fitment by engine serial number (ESN) or casting number before every head ships.

Replaces / Cross-Reference Part Numbers

OEM and reman numbers: 3991773, 3991771, 3991772, 3943627

Shipping, Core & Warranty

  • No core charge, no core return. This is a new casting, not an exchange unit.
  • Freight: ships crated by LTL freight. Freight is free to a commercial address with a forklift or dock. Residential, liftgate and terminal delivery can be quoted — call before you order.
  • Local pickup: available in Henderson, CO by arrangement.
  • Warranty: 1 year against defects in materials and workmanship.

Frequently Asked Questions

Is this head new or remanufactured?

New. It is a new casting assembled with new valvetrain components — not a rebuilt core.

Do I have to send back a core?

No. There is no core charge and nothing to return.

What else do I need to install it?

Plan on a new head gasket set and head bolts for the ISB 5.9. They are not included. Message us and we will match the right kit to your engine serial number.

How do I confirm it fits my ISB 5.9?

Send us your engine serial number (ESN) or the casting number from your old head. We verify fitment against 3991773 before the head ships.

5.9 or 6.7 — how do I know which head I need?

Send us your engine serial number (ESN) or the casting number on your old head. ISB 5.9 and 6.7 heads look alike but are not all interchangeable.

How long does delivery take?

Heads are crated and handed to the LTL carrier in 1–2 business days. Transit is typically 2–5 business days depending on your location.

Questions? Call JAK's Diesel at (720) 445-6249. See all Cummins B-Series / ISB parts or diesel cylinder heads.