The Four-Valve Swap Power Struggle Upgrade Part 2

Last month we presented Part 1 of this Two-Valve to Four-Valve modular engine swap on our '01 Bullitt Mustang. Our quest for a reliable engine combination that can push our SN-95 Mustang into the 9-second zone culminated in swapping the Mustang's high-strung 5.0L Two-Valve stroker for a tamer but better prepared Four-Valve 4.6L engine.

We left off with the long-block sitting in the engine bay. This month, we put the finishing touches on the little cammer. There were many roadblocks along the way before we turned the key for the first time, mostly due to the fact that we had started with not only a Two-Valve car, but a Bullitt at that, which has a number of model-specific parts that we needed to either swap out or modify to work.

Giving us the room to work, the lift to raise, and the tools to tighten was HP Performance in Orange Park, Florida. Our subject car has spent its fair share of time turning the company's Dynojet rollers, and it would soon be turning them again once we fired up the new modular mill.

In preparing the new engine assembly for installation into the Mustang, we discovered the SFI flexplate shield, which fit perfectly with the BC Automotive 4R70W automatic and the Two-Valve, now had a clearance problem with the new Four-Valve motor. It interfered with the lower outside area of the driver-side head. Though not technically SFI approved, the shield was notched a bit to provide the needed clearance.

"We've discovered over many installations of the Two-Valve motor and fighting the head gasket issues that it is much easier to remove and reinstall the motor from the bottom of the car," says Watson, "especially with an automatic transmission attached." Watson's wife, Wendy, came up with the idea of wrapping the engine in bubble wrap before installation. If you've done some painting while the motor was out--whether it was the engine or the engine bay or both that you painted--the bubble wrap can keep things pretty with its early warning system. Anytime something gets close to touching, the bubble wrap pops; you can stop and figure out the clearance problem.

Fine-Tuning The Fitment
At the time of the install, we decided to eliminate the connection to the heater core to improve engine coolant flow and to make more room for the larger fuel lines needed to run at the back of the engine. We used a preformed 90-degree-bend heater hose attached to the water connection on the back of the passenger-side head, and then used a reducer to connect the hose directly to the valley water tube eliminating the heater core in the loop.

Many subscribe to the modular motor cooling mod--adding an additional connection on the rear of the driver-side head, and routing the coolant to either the front crossover or to the inlet of the heater core. Our engine builder, Al Papitto of Boss330 Racing, doesn't believe there's much advantage to this mod on a Four-Valve. Papitto says the cooling mod is probably more useful on Two-Valve motors, which are more prone to detonation and would benefit from the better cooling in the rear cylinders.

One of the main concerns with this swap was hood clearance, as the short-runner intake we were employing utilized a 1-inch spacer between the upper and lower intake manifolds to maintain plenum volume on the modified straight-runner intake. It was a great relief when we were able to close the stock Bullitt/GT hood over the installed intake manifold, but we did have a problem after installing the throttle-body bracket on top of it.

Normally there are two cables attached to this bracket: one for the throttle and one for the cruise control, whose position is higher on the bracket. The hood just touched the top of the bracket where the cruise-control cable normally attaches. We could have ground off some of the top of the bracket, but since we weren't going to use the cruise control anyway, we just removed the entire area. The bracket looked better without the unused hole anyway.

The only other hood-clearance problem we experienced was with the alternator bracket. One of the bolts that secures the hoodscoop came down exactly on top of it. We cut off the unused length of that bolt, and the stock hood happily closed over the new powerplant--Bullittness maintained.

Connecting The Dots
Wiring was next on the agenda. The Two- and Four-Valve motors are remarkably similar in their components, however, they vary slightly with regard to the placement and location of certain items. You can attack this variance in one of two ways. Either use the Two-Valve harness and extend the wiring on the connectors that require extension, or use a Four-Valve harness as we did. After comparing the wiring diagrams on both the Mach 1 and Bullitt, it looked like the new Mach 1 harness was pretty close to plug and play. But it wasn't as close as we thought, as we discovered later when we started the car and found it ran on significantly less than eight cylinders. Ford wiring diagrams are not as user friendly as we hoped.

Watson used his extensive
instrumentation trouble-shooting background to start tracing from the EEC plug to the plug in the engine compartment to see where the electrons were running amok. Changes were required at the firewall interconnect plug. When installing the Mach 1 harness, we didn't use its transmission connector since we already installed a separate harness for the transmission during the previous 4R70W automatic upgrade. We later discovered four of the coil-pack wires were routed through the unused Mach transmission connector. Those four wires were cut and reconnected to the correct wires on the firewall connector.

Even with these variances, it's our consensus the Four-Valve harness is the way to go if you have that option. Wire lengths are correct and routed properly, and all the right plugs are attached. It looks OEM when you're finished. Stealth and the original stock look is something we are attempting to maintain, even with the massive changes in this original Bullitt Mustang.

It also should be noted the car already had a Mach 1 Automatic computer installed. This was done when the 4R70W was installed in the car, so no changes were necessitated there. Although the GT/Bullitt Two-Valve computer could be used to control a Four-Valve, we suggest you upgrade to a Four-Valve EEC--the main difference being the speed of the processor. With the ability of the Four-Valve motor to turn significantly higher RPM, the faster Four-Valve processor provides some headroom to run all of the background loops and properly controls the motor.

Fuelish Pleasures
Next up was the fuel system, which necessitated the death of some gray matter as we pondered how to feed and control the huge 95-lb/hr Acceleronics injectors. Pulling pump gas out of the sumped stock tank is a Barry Grant King Sumo fuel pump, which feeds a -10 braided-steel line that runs up to the engine compartment. This is where things get tricky.

The fuel rails supplied by Fore Precision Works are a work of art, but we were unable to do a rear inlet/front outlet flow pattern with them due to clearance problems with the coolant crossover tube on the front of the motor. There was just no way to attach a -8 line there, even with a 90-degree fitting. This, of course, wouldn't be a problem with the intended normal non-return system.

After much discussion, we decided to feed the rear of the rails with a T-fitting and allow the front end of the rails to deadhead. The -10 feed line comes into the engine compartment and splits into a pair of -8 lines. Each of these runs through a T-fitting that is screwed into the back end of each rail. After the fuel passes through the T-fitting, the supply lines then join at a Y junction before coming to a relative stop at the fuel pressure regulator. It's this holdup that pushes the fuel into the rails upstream.

Our concern with this arrangement was there was no flow through the fuel rails other than what was consumed by the injectors, which could cause a lean condition on the front injectors, especially if they drained the rails. We kept very close watch by reading the spark plugs on the front two cylinders after we had everything up and running. To date, we've seen no detrimental effects from this arrangement. This rear feed arrangement also located all of the fuel lines on the back of the motor and out of sight, cleaning up an already busy engine compartment, and again helping to maintain the OEM looks we after.

With the fuel system now sorted out, our attention turned to the fuel injectors. We expected that the potential power output of the supercharged Four-Valve motor could quite possibly suck the injectors dry, and at the time this was written, we were unaware of the RC Engineering 70-lb/hr units that we recently used in our '03 Terminator buildup. That being the case, car-owner Bob Watson spent a bit of time chatting with the folks at Acceleronics, who convinced him that the company's 95-lb/hr low-impedance injectors were the way to go.

We were skeptical of putting such large injectors in a car that was to be street driven, feeling idle and driveability would be compromised. The folks at Acceleronics explained that larger injectors, with larger internal discs that are controlled by the VersaFueler injector driver, actually provide better drivability. This is due to the peak-and-hold control scheme used with low-impedance injectors as opposed to the saturation scheme utilized on high-impedance injectors and OEM computers. Further discussion on this topic is beyond the scope of this article, but we did find that the 95-lb/hr injectors using the peak and hold control scheme gave the car better idle and driveability than the previously OEM-controlled, 60-lb/hr high-impedance injectors used on the previous Two-Valve motor.

Maintaining Control
While the Acceleronics injectors drop right in place of the factory pieces, there is a bit of rewiring needed to hook up the VersaFueler to the injectors. The injectors were coupled to the wiring harness with the familiar Cobra injector-conversion adaptors. We found that the VersaFueler unit fit neatly on the firewall near the heater core tubing.

Installation of the VersaFueler is very simple. The controller has two plugs with lengthy wires extending from each of them. These wires are routed to each positive injector wire. There is an input and an output plug from the VersaFueler, and each plug has the same arrangement of wire colors so you don't confuse cylinder inputs and outputs. You then cut the positive wire of each injector connection and connect the VersaFueler input wire to the injector wire coming from the EEC. Then connect the same color output wire from the VersaFueler to the wire going to the injector. Hook up the 12-volt supply and the ground and you're done.

The driver senses when that injector is called to fire and for how long; It then converts the saturated control scheme to a peak-and-hold scheme and operates the larger low-impedance injector accordingly. The EEC never knows it's there, and it doesn't affect the tuning. You may also use the VersaFueler unit to improve control of high-impedance injectors. So if you have some large injectors in place with idle or drivability problems, this unit could solve the problems without replacing your existing injectors. There are aftermarket engine management systems available that will drive large low-impedance injectors. These work well but compromise the benefits of using the stock Ford EEC to control all engine, transmission, and other vehicle functions. It also adds additional complications to the tuning process.

Extra Ribs, Please
Our supercharged steed utilizes none other than the Vortech T-Trim centrifugal supercharger, and a call to Vortech provided us with everything we needed for the conversion from Two-Valve motor to Four-Valve. Everything supplied by Vortech would have fallen in place, except that we wanted to use an eight-rib drivebelt system. Vortech does not offer a kit to accomplish this on our particular vehicle, but it did supply spacers and several components used for the eight-rib setups that are offered on other modular motors.

With this eight-rib setup, we did encounter some clearance problems. First, when the blower was spaced out appropriately to align its drive pulley with the wider belt, the drive pulley contacted the front of the reused Bullitt/Cobra alternator. We eliminated that with some minor grinding of the front of the alternator. Shortly thereafter, we discovered the coolant crossover tube wouldn't pass in front of the wider eight-rib alternator pulley. We took the crossover tube to Tracy Grimm at Speedfab, who extended the forward-facing tubes so the crossover tube would clear the front of the pulley.

The custom eight-rib system didn't stop there at giving us grief. When we tried to install the supercharger intake elbow, we found that it contacted the radiator before it completed its turn toward the fender. Again, this is no fault of Vortech, but it was caused by the supercharger having to be spaced forward to accommodate our custom eight-rib setup, in addition to the car having a thicker aftermarket radiator. To gain the needed clearance, we relieved the upper flange on the radiator. The T-Trim is now snuggled in and ready to bolt up to it's partner-in-horsepower crime, the Vortech aftercooler.

Although the Vortech engineers warned us the aftercooler we had on the Two-Valve would be restrictive at the power levels we were hoping to produce, we wanted to stick with it initially to best evaluate the gains of the Four-Valve motor upgrade itself. Last month we showed the inlet and outlet modifications done to convert the cooler from its Bullitt configuration to a Mach 1 inlet and '01 Cobra outlet. We also had the staff at Speedfab weld the fitting to mount Vortech's mini Race bypass valve, as we needed to upgrade from the base valve.

Now finished with our tasks in the engine compartment, a twist of the key brought the Four-Valve Bullitt Mustang to life. Next month, we're going to wrap up this quad-cam chaos with tuning, dyno testing, and track blasting. Check back to see how it all cammed out.