Since the aftermarket began churning out parts for our beloved Fox body, horsepower claims have abounded, and their validity often ends in mixed results. Edelbrock has been around for 65 years now and you don't stay in business that long by making false claims. Extensive research is the foundation for each one of its parts, which ensures that they work properly and perform well.
The 5-liter Mustang benefits from a vast aftermarket and there are quite a few choices when it comes to buying an intake manifold. We had an Edelbrock Performer EFI manifold waiting in our performance parts stash here at the office, and were curious to see how it would perform on our resident supercharged 5-liter pony.
The vehicle in question has graced the pages of MM&FF several times, first with the installation of ProCharger's P1-SC intercooled supercharger. This was followed by a complete exhaust system from Bassani, an FRPP Cobra R four-wheel disc brake conversion and a Clutchmasters clutch and aluminum flywheel (along with some much needed 3.55 rear gearing). The Mustang's engine remained stock from the throttle body to the oil pan with just the aforementioned bolt-on items increasing horsepower from 202.2 to 345.7 at the wheels at 10 psi. Torque had risen from 275.6 lb-ft to 390.9.
Edelbrock's Performer intake manifold (PN# 3821) retails for around $480 depending on where you purchase it, and the 50-state-legal unit is said to offer up to 37 hp with no loss of low-speed torque. Since the throttle body opening is cast for a 70mm unit, we ordered a new BBK 70mm throttle body and spacer from Brothers Performance; it just didn't seem right to choke off the new manifold with the stock 58mm unit.
Mechanically, the task of switching manifolds is not that difficult for the weekend wrench turner. We took our time, with frequent breaks for ice tea, and finished in less than a day. While we were switching manifolds, we took the opportunity to change the blower oil and polish the outer case. A swap on a naturally aspirated engine would take a bit less time.
Post installation, we took the supercharged Stang back to LaRocca's Performance in Old Bridge, New Jersey, to not only verify the change in power output, but also to make sure that the air/fuel ratio was still in check. The Edelbrock manifold offers a larger volume of air than the stock piece, and it turned out that the air/fuel went leaner from 11.5:1 to 12.5:1. The first dyno pull netted 393 hp, nearly a 50hp gain over the stock manifold, but the crew at LaRocca's was not comfortable with the lean A/F ratio. After making changes to the Mustang's custom computer chip, the air/fuel was back at 11.5:1 and we saw 383.5 hp and 407.8 lb-ft of torque at the wheels; a gain of 37.8 hp and 16.9 lb-ft of torque.
The resulting power increase was probably helped by the 10-psi of boost from the supercharger and, at this point, the cylinder heads and tiny valves are the biggest restriction now. Still, with 383 rwhp and a set of BFG drag radials, we were able to slash our previous best-elapsed time of 12.58 to a 12.25, and mph went from 110 to 114. We even went 12.55 on our 245/45x17 street tires. This just from a few hours in the garage on a Saturday, and we didn't even have to take off the valve covers. Read along to see what was involved.
 The Edelbrock Performer intake...  The Edelbrock Performer intake manifold is designed with a 0-5,500-rpm range and is a stock replacement item for '86-95, 5-liter engines. |  BBK's 70mm throttle body (PN##...  BBK's 70mm throttle body (PN## BBK1501) retails for $179.99, and its corresponding EGR spacer (PN# #BBK1502) sells for $59.99. The spacer and throttle body are CNC machined from aluminum, and are direct replacements for the stock units. |  Despite its 143,000-mile nature,...  Despite its 143,000-mile nature, this 302 is holding up well. The factory intake manifold is one of the reasons why 5-liters ran so well and produced so much torque. To begin, drain the coolant and remove the elbow from the throttle body. |