Back to Basics: Doge 12 Valve

Part Three: Engine Build and Bumper

Published in the June 2011 Issue June 2011 Ask The Expert
"The cylinder walls look good after 225,000 miles. There is some glazing, which is to be expected, but cross hone marks in the cylinder walls are visible and there isn't any damage or scoring. The piston heads and rings are in good condition as well. We should see minimal piston blow-by on our 6BT.
"This retainer plate is added to the camshaft gear to lock the gear on the camshaft. The helical teeth on the gear can cause the gear to back off of the camshaft under high rpm. This simple retainer is good insurance as we will increase the rev limit of this engine from 3000 to 4000 rpm.
"The Killer Dowel Pin is an alignment pin, installed at the factory to align the timing gear housing with the block. This should be checked and secured on any 1994 to 1998.5 6BT engine before it has the chance to cause catastrophic engine failure.
"The KDP retainer must be installed to prevent the KDP from vibrating out of position and falling into the gears below.
"Our head gets new Hamilton Cams 165-pound valve springs with lightweight 4140-alloy keepers to eliminate the possibility of valve float.
"The cylinder head has been machined and circular grooves have been cut to hold the fire rings in place above each cylinder.
"Big Twin Diesel cuts the fire-ring grooves in the head with a rounded cut so that the round edge of the ring seals positively around the ring. Many machine shops will cut the rings with a flat cut, which can be prone to leaking.
"Holes for each stud in the engine block are tapped, past the factory threads, until they bottom out, so the ARP studs are able to anchor to every possible thread.
"The fire-ring head gasket sits on top of the engine block with the fire rings in place around each cylinder
"Pat Liskey watches carefully as the head is moved into position to be lowered down onto the fire rings and gasket. Before the head is actually placed, they check, check, and recheck the position of every ring to make sure each cylinder seals exactly.
"The rocker arm pedestals must be machined down to allow clearance for the head studs. ARP Ultra-Torque is used on each thread in the engine block and with all stud nuts to achieve accurate torque on head studs. This eliminates the need for redundant multiple stage torque procedures of the past.
"We ordered this Baja bumper from Buckstop Industries with a Warn PowerPlant HD winch and four PIAA All Terrain Pattern lights.
"This old bumper had to go.
"The PowerPlant HD tucks into the Buckstop bumper while still allowing us to access the winch controls.
"Our Warn PowerPlant HD. 12,000-pound winch and 5 cfm, 90 psi air compressor will be integrated into our new Buckstop Baja bumper.

Our Back to Basics project continues as we are in the process of building a 1998 Dodge 2500 Quad Cab, powered by the Cummins 6BT (12-valve) engine. Our goal with this truck is to build significant horsepower and torque, making this truck a lot of fun to drive, while at the same time, tune this truck so that it can be driven as a daily driver with good fuel economy and practicality. Normally with a 12-valve engine-because they're not electronically adjustable-you have to make a choice: Either drive a tractor with great reliability and economy, sacrificing excitement, or drive a hot rod with big power, big smoke and limited drivability. Unfortunately, life's full of compromise and sometimes you just have to settle. However, in the case of this truck, we demand more. We want the best of both worlds and with the right tuning, we think we can have it all.

So far, we've replaced the transmission with a full billet, Fat Shaft trans from Ultimate Transmission. It's firm, shifts quickly, runs cool, and the Ultimate Transmission assures us that it will hold up to anything we throw at it. We're excited to put it through the paces. Next up, we prepare for power by building the head and installing a camshaft. This truck could desperately use a bumper too.


Next Step

When we were in Boise, Idaho, 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 as we took a ride in one of their 1000-plus horsepower trucks. As we drove along in four wheel drive at 40 mph, Liskey 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 Liskey about working on our Back to Basics project, saying, "We'll have what they're having."

In order to hold the new power we'll add to this 6BT with 225,000 miles on the odometer, we're going to need to address some critical points on the top end of the engine. We'll be adding a lot more fuel and air later, so intake boost and head pressures will go up. We could see between 60 and 80 psi boost pressure. The old (or a new) head gasket won't hold up to the head pressure. We'll need to fire ring the head, install stiffer valve springs, and hold the head down with studs instead of bolts. While we have the top of the engine torn down, we'll install a high-performance camshaft.


Valve Check

Big Twin Diesel took our 12-valve and removed the head for a full break down and machining. They removed all the valves and performed a complete valve job. Each valve was lapped and cleaned. The head was found to be free of cracks and flaws and was sent to the machine shop to be machined flat and grooved for fire rings. As the head was away for machining, they installed a Hamilton Cams 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.

While installing the new camshaft, Big Twin also installed one of its Killer Dowel Pin retainers. On 6BT engines, the killer dowel pin (KDP) works its way out of the of the engine block and can either fall down harmlessly, missing the timing gears, injection pump gears, and crankshaft gears to the bottom of the timing cover. Or it can get caught in those gears, break the cam key that keeps the cam timing in place, and cause catastrophic engine failure when the engine timing is lost and valves meet the pistons at inconvenient times. The retainer is simply a 1/16-inch thick steel tab that bolts into place, covering the dowel pin, so it can't vibrate out of place and single-handedly ruin your engine.



As the camshaft gear was installed, Big Twin installed a Hamilton cam gear retainer. The cam gear in this engine has helical cut teeth. The helical cut gears have a tendency to walk off of the spindle under high rpm. A stock 6BT revs up to 3000 rpm and really only fuels to 2800, so this isn't a problem. However, we'd like to increase our redline to 4000 rpm in this build, so we need to address the issue of a walking cam gear by adding a cam gear retainer.

After the cylinder head was machined, the valves were installed 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.


Building Barriers

Fire rings are steel rings that will create a steel barrier between the cylinders in the engine block and the cylinder head. These rings prevent the high compression that our 6BT will produce from blowing sideways through the head gasket. We'll replace the stock head bolts 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. The machine shop will cut grooves that are .0032-inch deep in a circular shape into the head. These grooves will keep the fire rings in place above each cylinder. With the fire rings and head studs in place, we can safely run turbo boost pressures up to 90 psi. If we were to use ARP Custom Aged 625 studs, we could hold up to 140 psi boost, which is often the case in Big Twin's 1000hp trucks.

Beefier Bumper

Next, we've got to do something about this bumper. We know the wheels and super trick paint on this truck aren't much to get excited about, but this bumper goes too far. We are tired of people staring at us as we drive by as they try to settle bets with other passengers in their car to see how many front teeth we are missing. And it gets really old when the girl at the drive-up window at McDonalds asks, "Will there be anything else today, Cletus?" To boost our image we ordered a "Baja" bumper from Buckstop Truckware to add some beef to the truck. We were also able to add some utility by ordering the bumper with options to fit the bumper with PIAA lights and a Warn PowerPlant HD winch, which provides us with a 12,000-pound winch and 5 cfm, 90 psi air compressor, tucked away conveniently on the front of the truck. Very cool.

The top end of our trusty 6BT is ready for some power. These modifications will allow us to add enough fuel and air to make this old truck a lot of fun to drive. With our new 47RE and a fresh top end on the engine, we've got a great foundation for efficient, drivable horsepower and torque. We're ready for the fun stuff.

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