We've been impressed with...
We've been impressed with the Performer RPM II since it was added to Edelbrock's lineup when the original Performer RPM proved limited in higher-power applications. Hardly a spendthrift with torque, the RPM II was the high-end king in this test, squeaking out the highest peak power, and an even more impressive ability to make power as rpm climbed high.
The issue with FAST is the same finicky demands for the right aftermarket hardware other aftermarket engine-management systems have shown. We pulled our hair out trying to get the engine to stop missing at 4,700 rpm until we changed from our original MSD magnetic pickup distributor to a TFI-style MSD distributor. FAST and the window spacing on the original MSD don't get along (neither did the AEM system we sampled a while ago), but the TFI/FAST combination ran great. Aftermarket engine-management systems all seem to accept the stock ignition system, too, including the distributor.
We ran our usual electric water pump and 1 3/4-inch Hooker headers. The electric water pump frees up a bit of horsepower; the generously sized long-tube headers help build it. Comparing one dyno test to another is nearly impossible due to, among other things, variances in dynos, so we caution you to subtract 10 or more horsepower from our figures compared to an engine with full front engine dress.
As it was, our engine made 420 to 450 hp depending on the intake, so it was no wallflower. In the real world, we estimate our test mule would generate 360 rwhp when installed in a Mustang, running a full front-engine dress, breathing through streetable mufflers, and so on. Healthy enough, in other words.
And a final dyno disclosure-we ran this test on Westech's engine dyno number two. Heretofore all our testing has been on dyno one, which is a 901 SuperFlow. Dyno two is a 902, so it looks a little swoopier in the photos. Westech says the two dynos read within 2 hp of each other; since they dyno on them every day, we'll take their word on that.
Holley's SysteMAX II was right...
Holley's SysteMAX II was right in the hunt in this test. If anything, the Holley seems to have the slightest of torque advantages over its near match, the Trick Flow competitor. Holley's SysteMAX kits with cam and cylinder heads are also great power producers if you're looking for a comprehensive, integrated kit for your 5.0 engine project.
It doesn't take much eyeballing of the results to note the BBK and GT-40 intakes make up one performance group, while the Edelbrock, Holley, and Trick Flow form another higher-output group. This makes sense because the GT-40 is an older design that dates from the days of simple bolt-on Mustangs and originally designed for the warmed-up version of the 5.0 H.O. engine eventually released in the '93 Mustang Cobra. The SSI is BBK's entry-level intake designed to run as well as possible on light-duty bolt-on cars but not necessarily placate the more aggressive strip warriors. Aimed at the same end of the market, it's no surprise they run similarly.
On the other hand, the RPM II, SysteMAX II, and Track Heat are all marketed to the harder-core street-strip market. And these three musketeers make amazingly similar power. This is especially true of the Holley and Trick Flow intakes, which are never 4 hp apart, and indeed, measured within 1 hp of each other over 80 percent of the time. The Edelbrock is similar, but does trade in a few lb-ft of torque in the midrange for that much stronger a top-end.
To be more specific, the RPM II and the SysteMAX II/Track Heat pair make within 2 hp of each other as they climb to their power peaks, but the RPM II keeps making a little more power all the way to our 6,000-rpm test limit, whereas the other two begin falling off. This gains the RPM II 3 more horsepower over the Holley and Trick Flow.
In fact, the Performer RPM II was this test's top dog-the only intake to sneak past the 450hp barrier. It posted the highest peak power, both in rpm and horsepower, and it hangs on to its power-making potential longer than the other intakes. Some of these trends are not huge, but they are pronounced enough to label the RPM II as the most horsepower-friendly intake here.
Trick Flow has been in the...
Trick Flow has been in the 5.0 H.O. power hunt since EFI was new, and it shows in this Track Heat intake. If you're trying to separate the SysteMAX II and Track Heat results in our test, we'd have to say the Holley gives up a hair of torque in the midrange, but the Trick Flow seems more willing on the over-rev. That said, it's a close call either way.
Thinking about the BBK and GT-40? Don't think they aren't worth considering because they were 25 or 30 hp behind the high-achieving Edelbrock/Holley/Trick Flow tripartite in peak power. While their lower-rpm torque advantage is not enough to offset their top-end horsepower deficit in this crowd, up to 4,500 rpm they are ahead of the top-end specialists. If your combination doesn't often see more rpm than that, the BBK or GT-40 will drive better and go a few feet farther with a gallon of gasoline. Of course, that describes a daily driver; if yours sees only the odd track day, the BBK and GT-40 are worth considering. Of course, if revving action is what you're after, the top-end manifolds are your best choice.
Comparing the BBK and GT-40 is something of a mixed bag, as the twin-plenum BBK has several peaks and valleys, but finishes stronger than the GT-40 with an extra 5 hp and a better ability to hang in there at high rpm. The GT-40 responds with a strong midrange and by far the lowest peak horsepower rpm. That means it delivers its power a bit stronger and earlier, which is useful on the street or in heavier cars. On the other hand, the GT-40 positively dies at higher rpm. It is the only manifold in this test that truly dives at the top of the tach, so it's not a good choice for an engine that will see 5,500 rpm or more on a regular basis.
As always, the combination of engine, gearing, car weight, intended use and a hundred other factors will help you make your intake choice. But when it comes to easily purchased and installed 5.0 intakes, the street/strip market has an intake for every need.