Back to Basics: Dodge 12 Valve

We started out with this project by following the primal call that comes from within us to get back to the simple and reliable days of the Cummins 12-valve engine. The 12-valve Cummins, officially known as the 6BT, is a legend in its own right. Its rock solid design is from an age when a diesel engine was a true diesel. In 1989 Dodge began stuffing this tractor engine in its 3/4-and 1-ton pickups, ushering in the first era of a true commercial engine for use in a pickup. This engine was originally designed for Case tractors and then adopted for use in a variety of commercial applications. This early Cummins engine is ultra reliable. The 6BT is all mechanical, meaning that it doesn't require any electronics to function or run. It does have a crankshaft position sensor for the tachometer, but for electronics, that's it. The components in this engine are truly industrial strength, engineered to run for a million miles with proper maintenance. EPA who? Yes, that's right, the 6BT is from an era where emissions on diesel engines were not under such tight regulation and subject to the asinine liberal propaganda mandated laws that the Gore-ites are force-feeding us, the majority of normal US citizens (hey, we've all got our hot-button). You can actually get 18 to 22 mpg on average when driving a truck with a 6BT engine.

Why This Truck?

We chose a 1998 3/4-ton Ram as the project truck. First and foremost because this truck came with the 6BT engine that uses the Bosch P7100 injection pump. This pump is the commercial strength powerhouse that came de-tuned from the factory for use in these trucks. There is a ton of fuel just waiting to be unleashed in these pumps. The other reason we chose this year is because Chrysler produced its Quad Cab truck beginning in 1998 with rear doors that open. The all-mechanical 6BT was fitted in these trucks for six months before Chrysler began using the 24-valve electronic ISB Cummins. The second generation Rams were also a big step up in comfort and drivability compared to the preceding first generation. We found our truck with about 220,000 miles on it, in good overall condition, but suffering from a bad transmission. However, the engine, exhaust and intake were all completely stock, which is what we like to find. It tells us that the engine will generally be in pretty good shape on a truck like this. We were able to pick this truck up for a meager $4,500, flamed floor mats and all.

Our Goals

As an idea for our readers, we thought that it would be cool to take this classic platform and build a truck that could serve as an alternative to buying a new or newer truck. This would be a truck that has everything we love about the old 12-valve 6BT Cummins-reliability, simplicity, durability, low cost of maintenance and great fuel economy. But at the same time, wouldn't it be great if this truck also had big power, a rock-solid drivetrain and could blow the doors off of most diesel trucks in your city? The challenge with an all mechanical diesel like this is that there is limited adjustability in tuning an engine that's not driven by electronics. In the past, you'd have to make a choice. Tune the truck for reliability, work and drivability. Or tune the truck for race, power and speed. There really hasn't been a happy medium between the two options. Our goal was to cross over into both worlds by getting serious about mechanical tuning-to build a 12-valve that has it all. The beauty of this project is that you could build it all at once or take your time, begin with a solid platform, and build it as you drive it.

Transmission

The first place we started with this truck was the transmission. We'd need a built trans to hold the power we wanted and beside that, the old transmission was completely gone, so if we were going to drive at all, this would be the place to start. For this, we turned to Ultimate Transmission in Boise, Idaho. These guys have a reputation for building automatic transmissions that will hold 1000 plus horsepower in race applications. We also like them because like so many successful engineers, they use the track as their laboratory and proving grounds. The way a truck moves down a track is an indicator of how the truck is able to dynamically manage the power and apply it to the pavement as it moves through the gears. The right transmission and the way it's built and set up is a key to getting efficient drive power to the pavement on this truck. If there's not enough engagement in the torque converter at the right time, the power of this truck will run through the converter at full throttle and not provide the lockup we need to go fast. If the torque converter gives too much engagement, too early, the converter will not allow enough slip to let the turbos light quickly and easily, which would produce excessive smoke from the exhaust. We took the truck to Boise, Idaho where U.T. could outfit the truck with one of its full billet, Fat Shaft race transmissions. Dave Fleenor, one of the founders of Ultimate Transmission, took a couple days to walk us through our transmission build. Our new transmission includes designs that U.T. has pioneered to give us a transmission that would not only hold big power, but allow us to actually make that big power drivable on an everyday basis.

Engine

When we were in Boise working on the transmission with Ultimate Transmission, we heard about a builder in the area who was known to build some of the best compound turbo setups seen on a truck. His name is Pat Liskey, owner of Big Twin Diesel in Meridian, Idaho. As we met with Liskey, it was apparent that not only could they build a mean-looking set of turbos, they knew their way around building and tuning trucks as well. This much was apparent when we took a ride in one of their 1000 plus horsepower trucks. As we drove along in four-wheel drive at 40 mph, Pat poured on the throttle, the big ball-bearing chargers howled, and the truck began to slide diagonally across the pavement as we burned all four tires. When I looked over at the gauges, the truck was building 120 psi boost pressure as the speedo climbed as if it were a tachometer needle. Shortly after that, we approached Big Twin Diesel about working on our Back to Basics project, saying, "We'll have what they're having!"

Big Twin Diesel removed the cylinder head from our 6BT and did a full valve job. Each valve was removed, lapped and cleaned. The head was planed down so that it was level and machined for a fire ring head gasket. B.T.D. also installed a new aggressive street/strip camshaft with .310-inch of intake lift and .320-inch of exhaust lift. This new camshaft will provide better throttle response, more power, less smoke and lower exhaust temps. This elongated burn time in the cylinders will be a factor in helping the 6BT overcome its smoking habit. After the camshaft was installed, B.T.D. installed Killer Dowel Pin retainer to keep the timing housing alignment pin from working its way out and into the timing gears, as 12-valve engines of this vintage are known to do. When the cylinder head was reassembled, Big Twin Diesel fitted it with new 165-170 pound valve springs and lightweight keepers from Hamilton Cams. Heavier, high performance valve springs are needed because at high rpm stock valve springs can "float" the valves. This means that the springs don't have the tension needed to retain the valves in their closed position as the engine speed increases. Engines with high miles, such as ours, will also need the springs replaced because as spring tension weakens over time and use, a modified engine running higher head pressure can overpower a spring and actually suck a valve open at the wrong time, creating an ill-timed valve and piston meeting. The head was anchored to the block with ARP 2000 high tensile strength studs in order to keep the head fastened securely to the top of the fire rings, head gasket, and engine block.

Fuel

Big Twin Diesel began our fuel upgrade by replacing the stock lift pump with a FASS Titanium Series fuel and air separation system. We chose the Titanium pump because it packs all the power of the heavy-duty FASS system into a smaller, more compact unit. It actually uses the same pump as the HD system. Our FASS mounts to the underside of the bed on the driver's side. It will supply the P7100 injection pump with 200 gallons of fuel per hour at 45 psi as it separates water and removes contaminants and air from the fuel. Fuel that's free of air and contaminants means longer life out of our injection pump and injectors, plus better fuel economy.

Liskey at Big Twin Diesel told us we'd need around 550 cc's of fuel output from our P7100 injection pump to drive the turbos efficiently. Beyond the injection pump, we'd use 90hp injectors from Dynomite Diesel to atomize the fuel. We removed the injection pump and sent it to Dynomite Diesel to be built for higher fuel output. DDP converted our 180hp pump (that comes with automatic trucks) to a 215hp pump (these came in manual transmission trucks) before they built the pump for power. The 215 pump is a much better platform for building a hot pump. At the end of the day, DDP sent us back a big, bad pump that will flow 900 cc's of fuel. We won't be able to utilize all of this fuel with our 90hp injectors, but if we ever want to build this truck for racing, we'll have enough fuel on tap for 1000hp. However, for this build we're going for efficient, drivable power, so the 90hp sticks should provide enough fuel for the truck to build 600hp, but burn lean enough with the compound turbos to drive daily without being a smokey pig. Liskey timed the injection pump for 22 degrees of advance.

Along with our new fuel, we needed gauges to keep an eye on the truck's vitals. We chose to use ISSPRO's Performax line of gauges. These gauges allow us to run five gauges on only three wires. This system will actually support up to 17 gauges on these three wires, but five should cover the bases on this build. The Performax gauges use highly accurate sensors that provide a signal to an electronic processor that mounts under the dash. The processor sends the signals through the three signal wires up to the gauges. Each gauge taps into the wire using a plug-and-play style connector and pulls the signal that corresponds with that gauge. This will allow us to change the placement of any of our gauges at anytime by simply unplugging the gauge from one pod and back into another. No tools or further wiring needed. Liskey also installed a "tattle-tale" switch on the dash so we can recall the highest readings on the gauges from our last run or trip. We're running a turbo boost 1 gauge for a combined boost reading, a boost 2 gauge for a reading on the boost pressure generated by only the second (larger) turbo, a pyrometer, fuel pressure and transmission temperature gauge.

Turbos & Exhaust

As we toured Big Twin Diesel and viewed a few of Liskey's twin turbo builds, we began to understand that some of our project trucks needed to have his name on them. We were impressed by the level of precision that they put into their builds. At first glance, we liked the fact that his twin kits use all steel tubing, without any silicone boost tubes. Every connection is made with close tolerance fittings, grooved, o-ringed, and then sealed with hard V-band clamps, eliminating the potential for leaks or pressure loss until the air enters the intercooler. We also noticed that the BT turbo kit on 12-valve and 24-valve engines would allow the use of the factory transmission fluid-to-engine-coolant heat exchanger. Most twin kits require deleting this heat exchanger, which if deleted, severely decreases the truck's ability to cool the transmission. Fluid-to-fluid heat transfer is far more effective than fluid-to-atmospheric transfer.

The first component that will get booted out of the engine compartment for our new twin setup is the factory exhaust manifold. We chose to run a new manifold that's made by a company called Steed Speed. The Steed manifold is the next progression in exhaust manifolds. It's a one-piece manifold that's CNC-machined out of mild steel and then ceramic-coated for decreased heat soak and as a result, more efficient energy transfer. This manifold flows more exhaust and has much less restriction than the commonly used two- or three-piece manifolds we've been using for years. All of this adds to quicker turbo spool and a reduction in EGTs. These manifolds are 50 percent more expensive than the old two- or three-piece cast manifolds you see today, but our philosophy here is you get what you pay for.

After the exhaust manifold, we should note that all of the plumbing in this kit has been ceramic-coated and fiberglass-wrapped where possible to stop heat soak and keep the energy (in the form of heat) contained and moving through the pipes, pushing the turbines, and out through the exhaust as quickly as possible. We also really like the fact that all of the plumbing is welded together and any connections that are made are accomplished with V-band clamps. No nuts or bolts to come loose or leak after we put some miles on this truck during work, play or race.

The Big Twin kit we chose for this build uses a Garrett GTX4202R ball bearing turbocharger for the bottom (larger) turbo with a 75mm inducer compressor and a 105mm inducer turbine. The top (smaller) turbo is a Garrett GT3788R ball bearing charger with a 64mm inducer compressor and a 68mm inducer turbine. Part of Big Twin Diesel's secret recipe for this twin kit lies in its exhaust housings. Apparently, they run housings that are not specific to Garrett and even still will be further modified to Liskey's specification. Ball bearing chargers will provide significantly less resistance than thrust bearing chargers, which will decrease turbo lag and greatly improve drivability around town. You can actually hear the chargers spinning for 30 to 40 seconds after you shut the engine off. If ball bearing turbos have a negative side to them, it's that they are more expensive than traditional thrust bearing turbos and require not only oil lubrication, but must be cooled with engine coolant additionally. However, we've given up many creature comforts by driving a 13-year-old truck. We're walking the diesel purist's line by going back to basics and we've been fiscally conservative with our money in our original truck purchase. We've done this so we can afford the coolest hardware under the hood and in the drivetrain. So your spouse should either be able to relate to this sensible logic, or never take the time to peek under the hood and see what the old truck really has there. This kit has two wastegates. The top charger does not have an internal wastegate, so B.T.D. uses an external wastegate before the turbo that is actuated solely off of spring pressure to release exhaust drive pressure when boost levels reach a predetermined level, which will depend on the application. The bottom charger has an internal wastegate that's operated with a boost reference line and an actuator as seen on most turbochargers.

For the exhaust on the truck we chose to give the truck an unmistakable muscular look by installing an MBRP Smokers single stack kit with an 8-inch black powder coated stack. B.T.D. built 5-inch exhaust from the lower turbo back to the bed, where the 5-inch pipe expands up to 8-inch diameter.

Alternator & Starter

The starter on the 12-valve was getting pretty tired and it took a bit of turning to start the engine, so we replaced it with a Mean Green gear reduction starter, which has a 4.4 to 1 gear reduction, so it has 100 percent more torque available to turn the engine over. With this greater torque comes speed too, because the starter can turn the engine with much less effort. When we replaced the starter, we also replaced the alternator with a Mean Green high output alternator, which will supply 300 percent more charging power than our stock alternator, which will come in handy during our cold winters, where the engine's grid heater draws a lot of power and takes its toll on batteries.

Bumper, Lights & Mirrors

The bumpers that came on the truck had to go. We got tired of the taste of throw-up in our mouth as we viewed the truck in the parking lot. We picked up a set of Baja Bumpers from Buckstop Industries and fitted them with the optional Warn PowerPlant HD winch and four PIAA All Terrain Pattern lights. For the rear bumper, we added conventional truck utility lights. To replace the yellowed headlights, we picked up a set of clear headlights on eBay. We also acquired a set of heated and power aftermarket towing mirrors (factory replica) from eBay as well.

Bedliner, Tool Box & Diff Covers

The bed was sprayed with Line-X and we added a Weatherguard low profile aluminum saddle box for our tools and incidentals to be stored and locked in the bed. Differential fluids are kept cool with Mag-Hytec replacement covers on both the front and rear differentials.

Final Results

On the dyno, the truck laid down 539hp and 1042 ft./lb. with a stock fuel plate on the injection pump. With a modified fuel plate, it put down 612hp and 1,259 ft./lb. We've limited our numbers by limiting our fuel supply with 90hp injectors. Drivability is great. The turbos spool quickly and effortlessly. Like we mentioned earlier, the throttle is sensitive and the DDP P7100 pump supplies a ton of fuel, so you can't just mash the accelerator and go. It takes a little restraint to caress the throttle to drive the turbos, but little movements with your foot equal big movements with the truck. Normal driving produces a slight haze from the stack or less. Spirited, quick driving around town produces little puffs of smoke, not unlike a 12- or 24-valve Dodge with 350hp. Exhibition driving can produce excessive amounts of smoke (enough to make a black cloud that hovers about 8 feet above two lanes of the road) at first until the turbos light, but after they're spooled, the smoke cleans up and the stack puts out a gray haze through the duration of the full throttle run. At 70 mph, with overdrive locked up, you have to be careful with the throttle, because rear tires will break loose when throttle is applied too quickly. EGTs run fairly cool. Under full throttle acceleration, EGT readings will get up to 1,500 degrees by the end of the run. When towing at freeway speeds, we saw EGTs ranging from 900 to 1,200 degrees, depending on the grade. Our favorite thing to do in this truck is to light the turbos and dump a bunch of fuel into it at about 30 mph and make two of the nicest looking rubber tracks for about 100 yards down the street.

For more detailed information on any part of this project, please refer to our past issues, beginning with part one of the series in the December 2010 issue.