Check out Part 1 and Part 3 of our 426 Hemi Supercharger Install!
To refresh your memory, in the October 2013 issue, we let you in on an idea that was presented to us by Richard Nedbal. Apparently, he wanted to build an engine that seems to be conflicted by opposing objectives. Namely, he was going to build a high horsepower supercharged Hemi that is also reliable. The engine would be an upgraded build of a normally aspirated engine that he previously built. Since he knew the internals of this engine, he used computer simulation to predict that 1,400 to 1,500 horsepower should be achievable with only 10 pounds of boost. This month, it’s time to start the process.
During disassembly it became obvious that the original engine was in pretty good shape, even after 300 passes. After inspection, Mopar Engines West (MEW) was given the task of machine work, in preparation for the current build configuration:
- The block was checked, cleaned, decked, and the bores re-honed.
- The crankshaft and connecting rods were magnafluxed.
- Since blower pistons should be gas ported, ports were added to the current pistons, and the skirts were coated.
- Diamond Racing Pistons suggested increasing the wall thickness of the wrist pins, so the rotating assembly had to be rebalanced.
- The heads were disassembled and checked. They required a valve job, and that new springs and locks be installed.
- Blower engines typically use two drift keys to make sure the blower hub doesn’t move. So the extra drift key slot had to be added to the crankshaft.
Making changes in regards to engine configuration many times means changing, adding or replacing some of the parts. In this case, the only new parts that we need to add are the blower and new fuel injection components.
For this engine we bought a used Mooneyham 10-71 blower from a friend. This is a great blower with racing seals, and is probably the reason that it produced a little more boost than the computer predicted. Last month, we told you that the computer predicted that we would have to overdrive the blower slightly, since a 10-71 is a tad small for a 572-inch engine. (Spoiler alert) In reality we ended up at a 1:1 drive ratio with a 14 mm Gates belt.
The upward pulling-force that the blower imparts to the crankshaft snout can easily exceed 1,000 pounds, so the solution is to install a crankshaft bearing-support cradle to help offset the force. Of course that takes up valuable room at the front of the engine, but it has to be done if we really want the bearings to live for any length of time.
If you have available room, it’s always better to inject fuel sequentially at each intake port. If using a blower, we feel that you also need to inject fuel above the blower to keep it cool. The intake used is a 16-bolt Indy Cylinder Head manifold. It was easy to use injectors below the blower base, since there is room to mount the fuel rails etc., and we used an injection plate from BDS for the injectors above the blower.
People usually ask about running sequential injection, which makes sense for the port mounted injectors, but how about the injectors above the blower? Those are also run sequentially since it really doesn’t matter up there.
The EFI System
I am a firm believer in the FAST fuel injection system, and use it for all of my builds, and this will be no exception. The EFI computer (ECU) has to be compatible with multiple drivers, since we’ll be driving 16 fuel injectors (rated at 125 lb/hr), instead of just eight. We’ll also be using coil-near-plug technology, so the FAST XIM ignition controller will be used. Sequential injection and coil-near-plug technology both require a camshaft signal. This is so that the ECU knows the beginning of the engine’s cycle. So, we’ll address sensor location as well.
Since there’s no room for a laptop in a dragster, the ECU must have internal data-logging capability. In addition, to minimize the corrosive effect of alcohol, our application will also require that the ECU hold two programs. We will need one for running the engine with pump gasoline, and one for running methanol. The reason for this is so we can warm up the engine on gas, and then switch to methanol for the race. Once the race is over, we can switch back to gasoline, thereby clearing the corrosive methanol from the system. We use an electric priming pump with Jiffy-Tite quick disconnect fittings to swap the fuels. It works well and takes only a few minutes to perform the switch.
They don’t make electric fuel pumps that will feed a 1,500 horsepower engine drinking methanol. If you do the math, you quickly see that the real problem is not pressure, but fuel volume at the higher, required EFI fuel pressures (greater than 45 PSI), since you need twice as much methanol as you would fuel. Brake specific fuel consumption (BSFC) for a normally aspirated gasoline engine is in the .5 range, but the BSFC for a methanol engine is twice that, and supercharging steps it up even more. So, if we have a 1,400 horsepower engine x 1.3 (BSFC estimate), it gives 1,820 lb/hr. I use 6.2 lb/gal for gasoline, which is a little light for methanol, but that gives a flow of 293 GPH or 5 GPM. I have to use a belt-driven mechanical fuel pump such as the Aeromotive 11105 to handle this. Since a mechanical pump’s volume will vary dramatically with rpm, you need to use a fuel regulator specially designed for this task. I used Aeromotive for all the fuel system components.
For the most part, assembly is just like any other normal engine assembly. We used coated Calico bearings, and set the main clearances a tad tight (.0025-inch) to allow for expansion of the aluminum block. We installed the new main studs, and Crower rod bolts with new AMS5844 bolts (rod bolt torque of 95 lb/ft.). We degreed the cam using the Jesel belt drive, and test fit the bearing support cradle. Everything was moving along smoothly. Next, we installed the Milodon 10-quart oil pan and the Titan oil pump.
Everything was going along smoothly until we tried to mount the Meziere water pump. No matter what was tried, it was not going to clear the blower belt. Most alcohol-fed blower engines don’t use water, so who cares about a water pump? But, since the Top Dragster class is primarily a bracket class where hot lapping is a definite possibility, and we wanted a car that we didn’t have to tow into the staging lanes or back from a run, we needed water.
AR Engineering makes these cool adapters PN AR245 that can be used with a remote water pump. We had to drill and tap extra holes for the -12 AN fittings, because no hoses could come forward from the block. A little drilling, a little tapping, an AN plug for the hole I didn’t use, a remote mounted Meziere water pump, and we have engine cooling!
I would have preferred to use copper head gaskets and stainless O-rings, but because of the large 41⁄2-inch bore size, there wasn’t enough sleeve material between the bores to allow it. We felt the Cometic gaskets would hold up well under the relatively low boost levels.
The heads were installed along with the Stage-V rocker system for the Millennium heads. All bolt torque was set using ARP Ultra Lube. Like we said last month, Millennium heads have raised ports, and therefore use spacer plates when a standard intake manifold is used. A neat side benefit to this is that the raised manifold allowed us to use a standard cast aluminum valley cover.
We bolted the blower in place, and used a 36-tooth lower pulley and a 32-tooth top pulley. (Second spoiler alert) Later we will find out while on the dyno that we don’t need any blower overdrive.