By the time you read this, the 2007 Grand National Roadster Show will have come and gone, and the hot rod selected as America's Most Beautiful Roadster will be well known. But when we were out visiting Hollywood Hot Rods in Burbank, California, just a few weeks before the event, Troy Ladd was still doing the down-to-the-wire thrash toward completion on his Brookville-bodied Deuce.
This is the roadster we've been watching come together for more than a year now. We showed you how the Brookville steel body was sectioned without screwing up the distinctive exterior styling cues of a Deuce roadster. And a few months ago, we followed some more subtle metalwork on that same roadster when the cockpit's upper perimeter was dressed up with some custom sheetmetal work. There is no such thing as too much detail when building an AMBR contender.
We were back at Hollywood Hot Rods just before Christmas. The body and chassis were away at the paint shop, but the engine was at the shop in Burbank, where Troy and the HHR crew were finishing it up. The engine is a 392ci Hemi that once powered a drag racer. It had been retired years before and was crated up and packed away when HHR found it. The crew machined it and rebuilt it with the high-performance components it deserves. But when you're going for AMBR, even the engine has to be as imaginative and distinctive as the rest of the car.
The goal at HHR, as usual, was to respect tradition but push it to the edge a little. In the case of this Hemi, that was accomplished by modifying a set of vintage Hilborn injectors with electronics in an undetectable way.
Converting a mechanical system to electronics is not a new idea, but in many applications, either the electronic advantages are compromised for the sake of appearance, or vice versa. HHR's goal was to take full advantage of computer programming, but in a stealthy way. It's old school, but with a brand-new curriculum.
Reigniting an Old FlameHollywood Hot Rods needed to keep the whole roadster looking vintage, and Troy found an old '60s-era Flame-Thrower distributor that is a perfect match for the car's look. But he also needed an electronic ignition to allow the computer to control the timing and work with the Hemi's EFI system. His solution was to convert the distributor to a PerTronix electronic system.
The old Flame-Throwers featured a dual point and dual coil pack design with opposite coils firing one bank of cylinders. Troy figured out a way to program the ignition so the computer can fire the cylinders with separate coils. He programmed the ignition to think it's firing individual coil packs (like on a new car), but in reality, it's only firing two coils opposite of each other. The spark is distributed through the Flame-Thrower, but the spark and timing are controlled through computer electronics instead of mechanical weights and springs.
It's a design he conceived on his own, but he created it with some help from the folks at Perfect Power, who confirmed that nobody has ever done this, but that it will work.
Troy really liked the looks...
Troy really liked the looks of these vintage Hilborn stacks found on eBay, especially since they mount at a canted angle instead of vertically. It would have been simple to machine these pieces to run injectors from the outside, but that would've meant cutting up old-time parts and would not have looked traditional.
The solution was to fabricate...
The solution was to fabricate components to hide the injectors and fuel rails. This pair of 1-inch spacers, machined from a length of 3x1-inch aluminum strap, mounts between the Hilborn system and the cylinder heads and acts as the manifold. The machining was done by hand on a mill, although they also could have been water-jet cut. The injectors feed into the spacer from below where they can't be seen.
The injectors connect to the...
The injectors connect to the spacer using an O-ring and these fairly inexpensive Holley replacement fuel injector bungs from the Summit Racing catalog. HHR welded the aluminum bungs in place, but the directions state that they can be epoxied in place as an alternative, using a product such as J-B Weld.
The aluminum fuel rails, available...
The aluminum fuel rails, available from Summit and other suppliers, were cut and drilled to fit.
...drilled to fit.
The injectors, fuel rails,...
The injectors, fuel rails, and wiring will be buried in this custom-fabricated sheetmetal valley pan.
Here you can see exactly how...
Here you can see exactly how the fuel rails will fit in the valley pan and where the fuel pressure regulator is housed. The parallel rails will be plumbed together with a T-fitting from the fuel feed line. The regulator will be plumbed in at the opposite end to control fuel pressure at the return line. This system, typical of fuel injection, creates pressure on the injector by controlling backpressure, which forces fuel into-instead of past-the injectors. According to technical sources such as Kinsler, this type of parallel plumbing provides increased fuel capacity and reduced fuel velocity in the rails, and provides better fuel distribution. According to Troy, the hardline plumbing lines will hold the rails in place, although HHR will reinforce the connection with a small L-shaped strap from each rail to the valley pan.
This is the fuel-pressure...
This is the fuel-pressure regulator that is shown in photo 7 in the pan (this Aeromotive product is listed as an injected bypass regulator in the Summit catalog).
The valley pan will be sealed...
The valley pan will be sealed by the ribbed valley cover on the left, which was machined from a larger aftermarket cover similar to the one on the right, which was too large.
The vintage injectors will...
The vintage injectors will be kept in their original position on the Hilborn system, but they can be plumbed to generate a vacuum signal because they are located below the throttle plates.
This distribution block will...
This distribution block will end up on top of the valley cover, where the barrel valve would ordinarily be on a mechanical system. Rubber high-pressure lines will run from the block to each of the old mechanical injectors, which are now being used to pull vacuum from each port. The vacuum will be balanced and run to the manifold absolute pressure sensor, which provides vacuum information to the computer. The computer then uses that info to calculate the correct air/fuel ratio.
The TPS (throttle position...
The TPS (throttle position sensor) was screwed to a fabricated aluminum block fastened out of sight onto the throttle shaft at the far end of the Hilborn unit.
This is the electronic fuel...
This is the electronic fuel and ignition management system HHR is using to run the EFI, starting with the ECU (electronic control unit) on the left. It is the Pro Race System (PRS) from Perfect Power, a stand-alone electronic control system. Stand-alone systems are universal applications for any car, and don't contain any pre-determined fuel or ignition settings; they are programmed completely by the user. By running the engine on a dyno and testing it under various conditions, you can use your laptop computer to precisely adjust each of the points on the fuel maps for optimum performance under any condition.
When everything is assembled,...
When everything is assembled, including the custom-built aluminum front piece, there is nothing visible to the naked eye that would hint that this is not a vintage Hilborn mechanical fuel system. But the fuel system has been precisely tuned and its functions are monitored by up-to-date technology.