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Call or Text (352) 722-5295The valvetrain on the 1998.5-2002 5.9L Cummins
The 24-valve ISB runs a cam in the block with solid lifters, pushrods and rocker arms, and four valves per cylinder. Valve bridges let each rocker open a pair of valves at once. Solid lifters mean lash is set by hand, but the 24-valve runs a much longer lash interval than the 12-valve did. The 2001-2002 High Output engine also got powdered-metal valve seat inserts. This collection also holds rebuild parts that work with the valvetrain, including MAHLE pistons, rings and valve stem seals. Our Cummins hub covers the rest of the engine.
When to replace or upgrade
At stock power, valvetrain parts usually come out during a rebuild or a top-end job. Stem seals, pistons and rings are rebuild parts, and the MAHLE pistons here come in standard, .020 and .040 oversizes to match the machine work. Upgrades come in when the engine is asked to do more. Stiffer valve springs and stronger pushrods are sold for higher rpm, higher boost and exhaust-brake back-pressure duty, and stiffer springs are a common part of building for high boost or heavy exhaust-brake use.
Stock replacement vs. upgrade
For a stock rebuild, the Cummins genuine complete rocker assembly puts the factory parts back, and MAHLE intake and exhaust valve stem seal kits handle the seals. For more boost or an exhaust brake, the options here include XDP high-boost valve springs and a performance spring and retainer set, Hamilton Cams 110 valve springs, and pushrods from XDP and Hamilton Cams, whose extreme-duty pushrods are 12 mm. Billet valve bridges come from XDP, D&J Precision Machine and Fleece Performance Engineering, and HD rocker arms from XDP and Hamilton Cams. XDP also sells a rocker arm trunnion set with a polishing tool. For a cam change, Hamilton Cams offers 24-valve camshaft combos in 178/208 and 188/220; call us with your turbo, fueling and how you use the truck before you choose.
What we carry
- Hamilton Cams: 24-valve camshaft combos, 110 valve spring set, high-performance rocker arms and extreme-duty 12 mm pushrods.
- XDP: HD rocker arm assembly set, rocker arm trunnion set, HD billet valve bridges, street performance pushrods, high-boost valve springs and a valve spring and retainer set.
- Fleece Performance Engineering and D&J Precision Machine: billet rocker arm valve bridges.
- Cummins: genuine complete rocker assembly and rocker box gasket.
- MAHLE: pistons with rings in standard, .020 and .040, piston ring sets, and intake and exhaust valve stem seal kits.
Fitment notes
Many valvetrain parts are shared with later engines. Rockers, bridges, springs, pushrods and the Hamilton cams are listed for 1998.5-2018 or 1998.5-2024 5.9L and 6.7L Cummins. Pistons are not: MAHLE lists the 224-3355WR family for 1998.5-2002 and the 224-3354WR family for 2001-2002, each in standard, .020 and .040, so match the year range and the oversize your machinist calls for. Ring sets are listed 1989-2002 and stem seal kits 1998.5-2002. The Cummins rocker box gasket is cataloged for 2003-2024, so check it against your truck. Verify by VIN.
Frequently asked questions
What is the valve lash spec on the 24-valve 5.9L?
Set it cold at 0.010 inch intake and 0.020 inch exhaust. The 24-valve runs a much longer lash interval than the 12-valve, but set it again any time you replace rockers, bridges or pushrods.
Do I need upgraded valve springs?
Not on a stock truck. Stiffer springs are sold for higher rpm, higher boost and exhaust-brake back-pressure duty. If you are adding boost or running an exhaust brake hard, they belong on the list along with stronger pushrods.
Which MAHLE piston fits my engine?
MAHLE lists one piston family for 1998.5-2002 and another for 2001-2002, each in standard, .020 and .040 oversize. Match the year range to your truck and the oversize to the bore work your machinist did. If you are not sure, call us with the VIN.
Do these rockers and bridges fit a 6.7L too?
Many do. Most rocker, bridge, spring and pushrod listings here run 1998.5-2018 or 1998.5-2024 and cover the 5.9L and 6.7L Cummins. Check the year range in each title before you order.
Not sure what fits? Call the shop at the number in the header, or use the fitment checker on any product page. We install everything we sell.