2004.5-2007 Dodge 5.9L Cummins Valve Train Parts

Valve train on the 2004.5-2007 RAM 5.9L Cummins

The common-rail 5.9 is an overhead-valve inline-six with a cast-iron head, four valves per cylinder and a solid-lifter camshaft. Every 2004.5-2007 engine is the 325-hp rating at 17.2:1 compression. The cam moves the pushrods, the pushrods move the rockers, and on a four-valve head each rocker presses a bridge that spans a pair of valves. With solid lifters there is no hydraulic take-up, so lash is a set dimension: intake 0.006-0.015 in (set at 0.010 in) and exhaust 0.015-0.030 in (set at 0.020 in). Rocker bolts torque to 27 ft-lb and valve cover bolts to 18 ft-lb. The top end changed for 2006. The 2003-2005 engines use a black plastic breather cover on an aluminum rocker housing, while 2006-2007 engines got a one-piece molded plastic valve cover with an integral breather filter and a single multi-wire injector connector.

What wears and why

At stock power the long block is not where these trucks give trouble; the fuel system and bolt-ons usually fail long before the iron does. The valve train problem documented on this engine is dropped valve seats after repeated high exhaust-gas-temperature excursions, mostly on fueled trucks still running the stock turbo. The symptom is a sudden miss or knock, and the damage can leave metal in the cylinder. Max EGT guidance for 2004.5-up engines is 1,500 F, and TDR writers keep it under 1,300 F on long pulls. The other way owners end up on this page is an injector job. TDR reports injector failures particularly on common-rail trucks past 150,000 miles, and the exhaust rockers have to come off to replace an injector. With the rockers already out, it is the right time to look over the rockers, bridges and pushrods and set lash back to spec.

Stock replacement vs. upgrade

For a stock or lightly modified truck, OEM-grade parts are the match. Genuine Cummins covers the complete rocker assembly (4995602), the rocker box housing (3974981), the rocker box gasket (3963379) and the connecting rod (4943979). MAHLE covers the rebuild side: top-hat style exhaust valve stem seals (SS45963), a valve stem seal kit (SS46108), pistons with rings in standard, .020 and .040 oversize (224-3673WR) and matching ring sets (S42170). The upgrade parts are for engines that are already apart with a build plan: heavier valve springs, tool steel retainers, heavy-duty and extreme-duty pushrods, billet and forged valve bridges, heavy-duty rocker assemblies and camshaft combos. If you are buying a reman long block instead of rebuilding, match the 17.2:1 compression ratio.

What we carry

• Cummins genuine rocker assembly, rocker box housing and gasket, and connecting rod.
• MAHLE pistons with rings, piston ring sets in standard, .020 and .040, and valve stem seals.
• Hamilton Cams 178/208 and 188/220 camshaft combos, 103# springs, a 110 spring set, tool steel retainers, high-performance rocker arms, forged bridges and 12 mm extreme-duty pushrods.
• XDP heavy-duty rocker arm assembly set, rocker arm bolts, a rocker trunnion set with polishing tool, billet valve bridges, high-boost and performance spring sets, and street performance pushrods.
• D&J Precision Machine billet rocker arm valve bridges and Fleece Performance Engineering billet rocker arm bridges.

Fitment notes

Many valve train parts are shared across the 24-valve 5.9 and 6.7, so their titles carry ranges like 1998.5-2018 or 2003-2024. A few are narrower. The MAHLE 224-3673WR pistons are titled 2005-2007, while the S42170 ring sets are titled 2004.5-2007, so a 2004.5 owner should confirm piston fitment before ordering. The Cummins 3974981 rocker box housing is titled 2006-2018, which lines up with the 2006 valve cover change; on a 2004.5-2005 engine, order covers, gaskets and injector harness parts by year. XDP street pushrods come in 3/8 in and 7/16 in, and oversize pistons have to match how the block was machined. The 2007 model year includes both 5.9L and 6.7L trucks, so confirm the engine, then use the fitment checker or verify by VIN with us.

Frequently asked questions

How often should valve lash be checked on a 2004.5-2007 5.9L Cummins?

The guidance is to check and adjust at 150,000 miles. Set intake to 0.010 in and exhaust to 0.020 in; the acceptable ranges are 0.006-0.015 in intake and 0.015-0.030 in exhaust. Torque rocker bolts to 27 ft-lb and valve cover bolts to 18 ft-lb when it goes back together.

Do the rockers come off to replace injectors?

Yes. The exhaust rockers have to come off for injector replacement on this engine, and the rocker bolts go back at 27 ft-lb. Since the top end is already open, it is a good time to check lash and look over the rocker hardware.

What causes dropped valve seats on this engine?

Repeated high-EGT excursions, mostly on fueled trucks still on the stock turbo. The warning is a sudden miss or knock. The 2004.5-up guidance is a 1,500 F maximum, and TDR writers stay under 1,300 F on long pulls.

Will a 2006-2007 rocker box housing fit my 2005?

Not without checking. The 2006-2007 engines use a one-piece molded plastic valve cover with an integral breather and a single injector connector, while 2003-2005 engines use a separate breather on an aluminum rocker housing with three pass-through connectors. The Cummins 3974981 housing is titled 2006-2018, so a 2004.5-2005 owner should confirm fitment by VIN first.

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.