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Plug and play your EFI

Dan Burrill September 20, 2022 Tech

Plug and play your EFI for more power and a retro look

Hot rodders and car builders by their nature are visionaries. They are able to start with an idea, imagine how it is going to work and go with it, no matter how long it takes. Scott Merrell of Classic Connection is a good example. Three years ago, Merrell along with two other like-minded individuals bought two Ford GT40 Mark 4 chassis and bodies from Fran Hall at Race Car Replicas (RCR). Then, instead of the traditional 427 FE engine/transaxle combination, they decided to power these cars with the new Ford Coyote crate engine.

For those who are new to this, Ford Racing’s all-aluminum 5.0-liter Mustang crate engine is a modern 5.0-liter 32-valve dohc V-8 that uses advanced features such as Twin Independent Variable Camshaft Timing (Ti-VCT) to deliver 420 bhp at 6500 rpm and 390 ft.-lb.-plus of torque at 4250 rpm (with premium fuel). The lightweight aluminum cylinder block features cross-bolted main bearing caps and thick main bearing bulkheads for bottom-end strength. Optimized oil drainback and windage control improves high-rpm performance. The headers that come with the engine are designed for any late model Mustang, or an early model Mustang that has chassis modifications, or early street rods or pickups. These headers can be used by hooking an exhaust system to them, and they work very well.

Now comes the rub. Merrell and his crew want to use the sexy, exotic, 8-Stack fuel injection system. It puts out more power than the stock fuel-injection unit, and it has the retro look of the 1960s. The only problem was that no one made the intake manifold, or the wiring harnesses or the computer for that matter, to make it all work.

The crate engines sold by Ford are sold without the alternator, belt and pulleys. These parts are sold separately in what Ford calls their alternator kit.
These engines come from Ford with a 1-piece plastic pan gasket, with a built-in windage tray.

“Well, I approached Bob Hockenberry, who at that time owned 8-Stack Injection, and Dale Schaller, his number one guy, about building the mechanical system for the Ford Coyote configuration,” says Merrell. “And they both got on board with it in very short order.”

So Merrell ordered three of the Coyote crate engines from Ford. Two of the engines were shipped to his shop in Sequim, Washington, for fitting purposes in the two GT40 cars. The other engine was shipped to 8-Stack in Youngstown, Ohio, so they could do the pattern work and engineering to build the manifold and the Weber look-alike throttle bodies with the internal fuel injectors.

“The whole concept behind this was to build a 21st century technology engine, with 1965 looks, and do it with a computer system that is plug-and-play,” says Merrell. “The other important goal was that there was to be no after-install tuning.”

The Serpentine belt on this engine is a very deceiving belt configuration and routing. When you first remove the belt from the manufacturer’s sleeve, and you look at the 68-in. length, it is difficult to figure out how it is routed on the front of the engine, unless you have a factory diagram. Here we have mounted the turnkey AC compressor and aftermarket power steering pulley system.
Due to space restrictions, we use the remote oil cooler and oil filter adaptor. It is located on the left side of the engine where the oil filter normally goes.

The only way this concept could be utilized was by having a consistent engine supply with a consistent base, with no internal modifications. So the Ford coyote engine at that time was the perfect choice, not only because of technology that was in it, but also because Ford Motor Company came out and said that that was going to be their performance engine for the next 10 years, and it was also going to be their production motor for their Mustangs and light trucks. The Coyote is a ready-made base engine platform.

Ford’s engine program supported Merrell’s idea to build a computer program to make it plug-and-play, with the idea that it could be used in other applications. As it turned out, it’s taken a year and a half to put the mechanical parts together on the engine. Then it’s taken another year and a half to find a quality computer manufacturer, and a quality programming company, to build the program.

“The computer and the program are the brains,” Merrell says. “We needed these two companies to satisfy my ideas as far as building a real out-of-the-box plug-and-play aftermarket fuel-injection system that looks like 1965 Weber carburetors.”

Next up, the stock harness is removed from the intake manifold and set aside. Note the deep open valley below the intake manifold.

The engines being used are right out-of-the-box, 5-liter, 302-cu.-in. and weigh 400 lb. each. This is 60 lb. less than the original small-block Ford. This is the only normally aspirated engine that’s ever been designed and built that is capable of 1.5 bhp per cubic inch. That tells you how good the design is.

The next obstacle, once they got to the point of seeing a reasonable time frame for having the dyno work done and the computer program built and functioning, was they needed a test bed.

The two Mark 4 GT40s were not and are not even close to being completed. So, late last year Merrell worked out a deal with Karen Salvaggio to purchase her old Factory Five Daytona Coupe. It was a dedicated race car and had been retired when she built her new Daytona Coupe.

Starting at the front, the coil pack connecters are carefully removed. On the front of the heads are the leads for the cam sensors. The gray plugs on the top of the coil pack covers are for the injectors on the stock manifold. The coil packs sit on top of the spark plugs.

So Here’s How it Works

For this application, the Canton oil pan is installed on the engine. The stock Ford pan is a rear sump operation. This engine was designed for the Mustang and they had to go to the rear sump pan because of the “K” member. Most of the performance applications don’t have a “K” member so they use front sump pans rather than rear sump pans. It is a better system because the oil is that much closer to the oil pump, which means less chance of having a cavitation problem. Not every vehicle will accept the front sump pan and, if that’s the case, we use the stock pan. Also the Canton oil pan is used with this engine because it has a deeper front sump.

The very impressive 8-Stack system has that shiny retro fuel-injection look. (In the 1960s, guys were putting the original Webers on everything imaginable, including the 35-bhp Volkswagen Beetles.)
8-Stack uses this unique bell crank to open and close the throttles.

These are the green intake O ring that are located on the bottom of the stock Ford intake manifold. They are reusable. This manifold has been CNC-machined to accept this type O rings. When changing out the stock manifold for the 8-Stack manifold, simply remove the green O ring and install them in the new manifold. These are installed dry, no lubricant. “For an old school guy like me, who has worn out about a dozen gasket scrapers over the course of my lifetime, these new O ring, and the oil pan and the windage tray are really neat innovations from Ford,“ says Merrell. “You can install and remove them as many times as you want without having to use any gasket seal or lubricant.”
Next comes the trial fit. Once we are confident that we are ready, the tape is removed and the manifold is fitted and bolted in place.
The harness comes ready to plug in and everything is labeled, so there is no wondering what comes next.
Going from the stock Ford fuel injection to the 8-Stack is a very easy change to make. As we stated before, this literally is a plug-and-play system. This is the forward section of the ACM harness, and this is the part that we are going to attach to the engine. It has an aircraft quality, waterproof, 60-pin quick disconnect, that is designed to be disconnected at the firewall.  “We have incorporated this water-sealed quick disconnect in the harness so that if a customer needs to pull the engine out of their vehicle, they don’t have to tear out all the wiring under the dashboard just to get the engine out,” says Merrell. “Also note the yellow tags. Every connection on this harness is marked and coded as to where it goes on the engine.”
“When matching up and plugging in the connectors, the easiest way to do it is to start at the front and work your way back,” says Merrell. “Read the labels and plug it in. All the wires are marked.”
These are the two O2 sensor leads and the drivers for the O2 sensors. These two are exceptionally long because they don’t fit this set of headers. They are exceptionally long because they go in the Daytona Coupe. These can be custom-built to any length depending on the customer’s header system.
We also use an IAC system (Idle air control motor). This is what stabilizes the airflow system at 1500 rpm and less. And that goes on just like that. The reason is that this 8-Stack system has a difficult time balancing airflow at low rpms, so this IAC works off a vacuum signal in the computer and the computer opens and closes the IAC to balance the fuel mixture in the vacuum at low rpms.
These are the cam sensor connectors. Intake side at the top, exhaust side is at the bottom.
Hooking up the coils 5, 6, 7 and 8.
This is the throttle position sensor.
This is the rest of the harness from the connector back to the computer. It starts at the firewall and goes in under the dashboard.
Hooking up the coils 5, 6, 7 and 8.
Hooking up the coils 5, 6, 7 and 8.
These are the drivers for the coil pack. “So basically, when the customer gets this unit, and they get everything wired up on the engine, inside the car the other half of this quick disconnect has got the power leads and the three or four wires that go to the ignition switch and the starter, and that powers this computer,” Merrell says.
Now we are ready for the fuel system. We are installing the fuel manifold system for this particular engine because it will be used primarily on the race track. This is a parallel fuel system. This system is used to ensure that the last two injectors don’t run lean, which is a possibility with the street setup under heavy use. All cylinders receive the same amount of fuel with the parallel fuel system.
This custom application required a custom-built thermostat housing and expansion tank with the radiator service cap. It was fabricated by Merrell for the high-performance application, and it was necessary for fitting the Coyote engine in the Daytona Coupe for testing and tuning.

And for the final touch, the custom cast-aluminum coil pack covers are installed.
The complete package with the headers for the GT40.

The proof is in the Dyno verification. By going to the new 8-Stack fuel injection, Merrell and his team have increased the horsepower rating, with no internal changes to the engine, from Ford’s advertised 420 bhp to a verified 438 bhp. They also increased the peak torque rpm from 4200 to 5350, which is a huge gain. The only change made to the engine was to put on a competition oil pan, just for safety. This pan was built by Merrell and holds about 10 quarts; the whole system is about 12 quarts.


In 1964−1965, Peter Brock designed the Shelby Daytona Coupe to compete with Ferrari for the FIA World Manufactures Championship, which they won in 1965. There were six original cars built and all six still survive today. All six are collectors’ cars and carry a high value.

Several kit car builders have re-created the Daytona Coupe. Factory Five’s car is at the top of the list and some people buy them to build as dedicated race cars. Karen Salvaggio is one of those people. She has won two national championships with Factory Five roadsters. She and her now deceased husband bought this Daytona Coupe in 2004. She raced this car for seven years, and then the car was retired when she had a new one built. This car won two 25-hour races at Thunder Hill, California. The retired car has been sitting in a museum.

Now, as we mentioned, Merrell’s GT40s were not ready and he needed a race car for a test bed for the new engine and 8-Stack combination. So he called Salvaggio and ultimately bought the old race car. Former Shelby driver, Alan Grant, towed the car up to Merrell’s shop in Sequim, Washington.

Of course, the Coupe needed to be completely dismantled. All new parts needed to be ordered or fabricated, and the car needed to be extensively modified to accept the new Coyote engine. Coupe Connection has a full machine shop, which made it a lot easier to do fabrication and machining in-house, and not have to farm it out.

Merrell, along with Larry Reece and Duane Babinski did all the work on the Coupe, with the exception of the ceramic coating on the headers and side pipes. Working non-stop, the crew of three were able to have the car ready for the track in just a few months. The new paint scheme was designed and applied by Merrell to promote Coupe Connection, and to stand out from the other Daytona Coupes that are painted with the Shelby Identity.

Hand-lettered, just above the left-hand door, are the names of the three drivers: “Curly, Larry and Moe.”

The wheels are 17-in. with 9.5-in. in the front and 10.5-in. in the rear. Tires are Nitto 555 and the sizes are 275/R-17 in the front and 315/R-17 in the rear. The wheels are an aftermarket copy of the Ford Mustang FR 500 that came from American Muscle.

The instruments are all Stewart Warner analog. The transmission is a Tremic T-600 5-speed bolted up to the Ford Coyote engine, with independent rear suspension with 2:73 gears. The car has a stock Ford Mustang rack with power steering, a KRC variable pressure pump and a cooler.

There was a tremendous amount of modification to this car to make everything fit, so it really wound up being a one-off by the time the car was ready to go to the track.

“This allows me to change the pressure in the rack to either increase or decrease the speed of the steering and also the feel in the steering wheel,” Merrell says.

There was a tremendous amount of modification to this car to make everything fit, so it really wound up being a one-off by the time the car was ready to go to the track.


Coupe Connection
145 Bravo Rd.
Port Angeles, WA 98362
(360) 461-7248

Borla California
701 Arcturus Ave.
Oxnard, CA 93033
(877) 462-6752

Factory Five Racing
9 Tow Road
Wareham, MA 02571
(508) 291-3443

Ford Racing engines are available through any of the large parts houses or your local Ford store.


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