CUMMINS 12-VALVE FUEL SYSTEM & PUMP MODS
Fuel System and Pump Modifications
After some simple preventative maintenance and installing a performance-built Firepunk Diesel Performance transmission in this otherwise stock 1997 Dodge Ram 2500 to handle more aggressive performance upgrades it was time to really turn up the wick on the sleeper and make the "P-paw" truck begin to live up to its 12-valve Cummins potential. Owner Ryan Bean of Beans Diesel Performance in Woodbury, Tennessee, started the process by installing a set of ARP head studs, and then performed some relatively easy injection pump modifications to squeeze more power out of the mechanically fuel-injected Cummins.
Getting more fuel into a diesel engine is the key to making more power and the 12-valve Cummins engine is no different. Within reason, if we give it more fuel, it will make more power with more air down the road for improved throttle response and lower EGTS. To provide the mechanical P-pump on the Cummins engine plenty of clean diesel fuel, Bean installed one of their original single-bolt fuel tank sumps along with an Airdog II fuel pump and filter system.
Bean brought the truck down to Chattanooga, Tennessee, to run it on the Dyno Proven chassis dyno before and after the pump modifications. Before he tweaked the injection pump, he installed a set of ARP head studs to keep the head sealed to the block, a procedure he recommends before trying to squeeze more power out of the engine.
Installing head studs on the 12-valve Cummins engine requires machining the rocker arm pedestals to provide proper clearance between the stud’s 12-point nut and washer and the valve cover. Fortunately, Dyno Proven has a full machine shop on the premises so Bean was able to pull and disassemble the rocker arm pedestals and handed them off to be milled in the machine shop rather than having to ship them off or take them to another facility.
Typically, when installing head studs on an engine that’s running and still in the truck, Bean replaces one head bolt with a stud one at a time. However, with the 12-valve Cummins and the need to machine the rocker pedestals, he removed all of the pedestals to have them machined and then reinstalled them before moving on to the rest of the bolts and studs one at a time. Be sure to follow the recommended torque procedure and use the supplied ARP Ultra-torque fastener assembly lubricant to get accurate torque measurements. And, since the rocker arms and pedestals are removed and reinstalled, do not forget to readjust the valve lash. Bean uses .010-inch for the intake valves and .020-inch for the exhaust valves.
To improve airflow into the cylinder head, Bean installed a machined aluminum plate and spacer to replace the factory
cast aluminum intake plate and integrated grid heater. He also drilled and tapped the exhaust manifold for an EGT probe and installed an Edge CTS to monitor the engine vitals, including transmission temperature and boost with the add-on Edge harness modules.
After Bean completed the head stud installation and adjusted the valve lash, they strapped the truck to the Dyno Dynamics chassis dyno and he turned his attention to the injection pump. The first procedure was to install a Dynomite Diesel Performance fuel plate kit to increase fuel output. With the fuel plate installed in the truck, he picked up about 100 horsepower and about 125 lb/ft of torque at the wheels, nearly doubling the available power and torque originally measured on the truck.
Then he advanced the injection pump timing to 21 degrees, which is a lot of timing. Bean does not recommend going past 19 degrees advanced unless you install head studs. The timing advance only provided a few additional horses so unless the timing is suspected to be off on your truck or you’re really scrambling to squeeze that extra little bit of power out of the engine, it’s something probably best left to the pros rather than Diyers in the garage.
New governor springs from Dynomite Diesel Performance were the next pump upgrade Bean installed. The spring installation requires rotating the engine over by hand until the springs are aligned with a small opening in the side of the pump and replacing the springs, then rotating it over again to replace the springs on the other side of the internal assembly.
The governor springs control how high the truck will be able to rev, as can be seen by the dyno graphs. Even with the previous modifications, power and torque fall off steeply after 2,300 rpm, which doesn't give a lot of operating rpm range to work with. With the new springs installed, the engine revved freely to nearly 3,800 rpm, extending the power band and giving the engine a much larger operating range while also increasing the peak
horsepower slightly. At 2,800 rpm, before the new DDP governor springs, the engine made about 75 horsepower and about 150 lb-ft of torque, but after the spring install the engine is still making nearly 275 horsepower and over 500 lb-ft of torque at 2,800 rpm!
To finish things up, Bean installed the DDP boost-fitting elbow on the turbo outlet. The new fitting has a smaller orifice to allow more boost before the wastegate opens and help prevent it from opening prematurely. Peak power only increased by about nine horsepower but peak torque grew by close to 75 lb-ft with a peak of nearly 675 lb-ft of torque.
Installing the fitting took only a few minutes and provided excellent increases in power and torque, especially down low in the rpm range.
Including the head studs and machine work, the installation took a full day. Add in some time for the Edge CTS sensors, and Airdog fuel pump/filter system and sump, and you can fill a solid weekend with wrenching on your truck, maybe even longer if you have to wait for a machine shop. As usual, practice safe shop techniques, and if you doubt your skills or the techniques used, have your local diesel performance shop install your upgrades for you. UDBG