Mods 4 Mods

That happy times are these. I finally got my 4.6 Modular motor up and running on the engine dyno. Sitting for these long months since delivery by Mustang Parts Specialties, the '98 single overhead cam GT mill was finally installed and brought to life thanks to the guys at F.A.S.T. and Westech Performance, specifically Tom Habryzk, who single-handedly worked out the wiring harness to allow us to ditch the factory injection and install our very own F.A.S.T. system.

The F.A.S.T. fuel injection provided us the ability to fine tune each and every combination tested on the dyno, but more on the abilities of the F.A.S.T. system at a later date. Look for a full rundown on the fancy fuel injection once we install one of the new Kenne Bell superchargers on a fully built Sean Hyland 4.6.

Talk of the F.A.S.T. fuel injection and upcoming Kenne Bell blower test has gotten us all ahead of ourselves, so it's back to reality for a minute, but that doesn't mean we are backing out on performance. No loyal readers, we are all about performance here at MM&FF, so we decided to do more than just install the early wrecking yard special on the dyno and see what happens.

While stock is nice, it is for people who see the automobile as nothing more than simple transportation. It you feel a car is little more than a transportation device designed to bridge the gap between point A and B, then you can dismiss yourself and grab a double decaf mocchachino at the nearest yawn fest.

For those still with me, especially those looking for ways to bring the power of their early GTs up to late-model spec, we've got one heck of a series planned for you. Fear not late-model GT owners, we haven't forgotten you as the early GT build-up will naturally include the venerable PI heads and intake. Not just any PI heads mind you, but a set of CNC-ported heads, to which we will be adding a custom intake designed by yours truly. Not only has this intake never been seen, but the intake in question is also adjustable. Interested? We thought so.

While we certainly have grand plans for this particular 4.6, including a blower, turbos, and possibly a forged internal stroker, we have to start out somewhere. In this case, that somewhere is at the beginning as in, stock trim. Actually our baseline runs were made with the engine equipped with a Meziere electric water pump, a set of Hooker Super Comp long-tube headers and none of the accessories. The Hooker headers were run through a 3-inch dyno exhaust system consisting of 18-inch collectors and no mufflers. While we usually employ mufflers in our testing, we were curious about the sound potential of the much-maligned (early) Modular. As it turned out, the early motor surprised us by producing pretty impressive power-all things considered.

The use of the F.A.S.T. stand-alone fuel injection system allowed us to eliminate the mass air meter and associated inlet tubing from the power equation. Sure, that dismissed some important (and popular) performance components from the test regiment (such as cold-air intakes, aftermarket MAFs and inlet tubes), but we knew the power output would not be limited by the air induction system (ditto for the converters and cat-back exhaust).

Though Mustang Parts Specialties supplied a card indicating the plant was run prior to shipping, we did not know the history of this particular 4.6. We hoped it was healthy and ready to take some serious abuse. The last thing we wanted was to rebuild the motor before ever getting started. Working with the F.A.S.T. fuel injection, Habryzk had the early GT motor up and running in no time. After spending some time tuning the base fuel and timing tables, Tom eventually coaxed peak numbers of 260 hp and 341 lb-ft of torque. We managed to match the flywheel rating of the new (more powerful) GT motors, but before you get in an uproar about happy dynos and exaggerated power numbers, remember this reading was taken with long-tube headers, no MAF or air inlet system other than a 3-inch tube and cone filter and without any of the accessories. The idea was not to exceed the 260 hp offered by the late-model GT motor, but rather to establish a baseline to which we could improve upon. Given the difference between the early and late-model motors, we suspect a later GT motor run in a similar manner would probably be much closer to 300 hp.

Regardless, this first adventure with the 4.6 proved worthwhile, as not only did we manage to get the motor up and running, but we upped the peak power from a baseline of 260 hp to 400. Even discounting the nitrous, the 4.6 topped the 300hp mark and we still have heads, an intake and more compression waiting in the wings. We'll see ya next month with the next installment.

Regardless of the numbers, we now had our official baseline. Thanks to the repeatability of the F.A.S.T. injection system, back-up runs produced exactly the same power curves. We did not have to worry about the power changing due to ECT or ACT readings, as the changes to fuel and timing based on temperature were effectively zeroed in the programming. This is important as testing on the chassis dyno has shown that power can vary by 10-15 hp or more depending on the coolant and/or inlet air temp. When you are testing things like throttle-bodies that make only a handful of extra ponies at this power level, it is imperative to ensure repeatability. I have seen test results on more than one product that I'm sure were the result of temperature rather than any additional power. To ensure accuracy, we made every effort to run the motor at a constant water, oil and air temperature. Only this way can you ensure accuracy and properly verify the benefits of given performance components.

Since we had not only our baseline, but also a repeatable package, we decided to venture off and start swapping some hard parts. First on the list was a set of cams. Wanting more than 5-10 extra hp, we decided to go big in terms of cam profiles and selected the largest Xtreme Energy grinds available for the early 4.6 GT motor. The dual-pattern XE274H cams offered a 236/240-duration split along with .500 lift for both the intake and exhaust. A wide 114-degree lobe separation angle helped tame the cam somewhat, but the duration ensured that these Xtreme Energy cams lived up to the description of "Hot Street Cams" given by Competition Cams.

In addition to the "Hot Street" label, Comp Cams also recommended steeper rearend gears, a higher stall speed (if automatic equipped) and computer upgrades (otherwise known as chip programming). Our F.A.S.T. programmable ECU obviously fell under the last category, so we felt confident that we could provide any fuel or timing changes desired by the more aggressive cam profiles.

Though designed to operate effectively from 2,000 to 6,000 rpm, we were to find out in testing that the stock (early) GT intake manifold kept peak power well below 6,000 rpm. Still, we had high hopes for the cam upgrade.

The new XE cam profiles required a valvespring upgrade, as well. Comp Cams supplied a set of 26113-16 springs to provide sufficient seat and open pressure (along with the necessary coil-bind clearance) to ensure proper valve control.

After installing the springs and the new Xtreme Energy XE274H cams, the peak power jumped from 260 to 301 hp. Our early GT was now making at least as much as (and possibly more than) a later GT motor thanks to the power offered by the Xtreme Energy cams. The peak torque was up as well, by 5 lb-ft. Not surprisingly, the motor lost a bit below 3,400 rpm, but beyond that it was all good, baby. Check out the supplied power curve to see just how much extra power as supplied by the cam, but with the effective power band of 3,500 to 5,500 rpm, this cam would do nothing but improve acceleration. With as much as 50 extra horsepower available thanks to the cam swap, the gain in acceleration would be significant. In fact, we'd have to say that the wimpy stock intake and heads were now holding back this GT motor from making serious power.

While the speed density-based F.A.S.T. fuel injection eliminated testing of any MAFs or air intake systems, it did not stop us from testing one of the most popular bolt-on performance items available for the GT motor-namely a larger throttle-body. Aftermarket throttle-bodies have been around since the birth of fuel injection, and in the eyes of most enthusiasts, bigger is always better. We have shown time and time again that this is not always the case, but often times there is power to be had with the installation of a larger (or in this case a better flowing) throttle-body.

This is especially the case when you include the 90-degree power elbow that joins the throttle-body to the composite (plastic) intake manifold. The Accufab throttle-body and 90-degree mounting elbow outflow their stock counterparts by a wide margin, but as we found out, these two items were not the only restrictions to the induction system. Replacing the stock throttle-body and 90-degree elbow with the polished, billet aluminum pieces from Accufab resulted in power gains of 10-11 hp. The billet construction and show-quality polishing were reason enough to replace the crappy stock parts, but adding an extra 10 hp makes the deal a no-brainer. Look for more testing on the combo once we eliminate the heads and intake as the major restrictions.

While the Hooker full-length, Super Comp headers were installed from the outset, we were still curious about how much power they were worth over the stock 4.6 Mustang exhaust manifolds. To find out, we ran the motor equipped with the Hooker headers and then with the stock manifolds. Equipped with the Hooker headers, the 4.6 produced 307 hp at 5,200 rpm and 345 lb-ft of torque at 4,100. The Hooker headers were then replaced by stock manifolds.

Like the headers, the stock manifolds were run with a section of open pipe and no mufflers. The exhaust pipes measured 2.5-inches to match the outlet of the exhaust manifolds. Equipped with the stock manifolds, the power dropped from 307 to just 269 hp, a drop of 38 hp. Imagine, adding Hooker headers to your Mustang can be worth as much as 38 hp. Like most flow restrictions (inlet or exhaust), we suspect that the difference in power between the stock exhaust manifolds and the headers would only increase with elevated power levels.

The final test run on our test mule was to install a ZEX nitrous system. The simple wet system combined the nitrous and fuel together in a single fogger nozzle and sent the mixture through the throttle-body and into the (rather torturous) intake manifold. We made sure to raise the bottle pressure to the recommended 900 psi before testing. This was accomplished by placing the bottle next to a small space heater, but the preferred method is a dedicated bottle blanket.As expected of almost any nitrous installation, the gains were significant. We managed to reach 400 hp and (more impressively) 500 lb-ft of torque, but we feel that the extremely long intake manifold limited the ultimate power potential as the relative power gained dropped off past 4,800 rpm. Remember that the normally aspirated motor produced peak power at 5,200 rpm.