Hot-rodders are never ones to leave well enough alone, and the Muscle Mustangs & Fast Fords staff members are certainly guilty of that. After we completed Project Stolen Goods, our resident '93 Cobra, we wondered about the many what-ifs that we hadn't tried. This month, our what-if revolved around two main premises that involved two key players in the Stolen Goods buildup.
D.S.S. Racing's Tom Naegele felt that our big-bore (4.125 bore/ 3.25 stroke) 347 Boss engine should be making more than our current 400 (estimated) flywheel horsepower it had produced thus far. The components we chose for our induction setup were a little too mild to offer that level of peak power, but it did produce an abundance of torque, which is what we were aiming for. We had queried Anderson Ford Motorsport's Rick Anderson about which intake cam and heads to use, and he specified AFM-ported Trick Flow Twisted Wedge cylinder heads, an AFM B-41HR camshaft, and a Trick Flow Track Heat intake manifold.
Anderson's recipe delivered exactly what we wanted: a torque-oriented motor that would take advantage of a 3.27-3.55 rear gear ratio. Moreover, it would be perfect for real-world driving and/or coming off a corner or a stoplight. When asked about Naegele's expectation, Anderson noted that a different intake manifold should pick up another 20 hp, but in trade it would lose about 30 lb-ft of torque, and after all, we did build it for torque.
The Performer RPM manifold...
The Performer RPM manifold was redesigned a few years back, and the new RPM II can be had in a mean-looking black powdercoat (PN 71233). The manifold comes with everything you need short of intake gaskets and a tube of silicone.
With 358 rwhp and 376 lb-ft of torque, we were pretty satisfied with the way the engine build turned out. The torque makes the car loads of fun to drive whether on the street or at the track. We suppose it's those pesky LS1-powered ponycars that drove us to the intake-manifold test. We've seen bolt-on 346ci LS1s make the same amount of power as Stolen Goods, but their torque peak was much higher in the rpm band. That's not always a bad thing, though, as too much torque can make it difficult to get traction in low-speed situations.
During a recent editorial meeting, Editor Evan Smith made it known that he wanted our teal project car to nab an 11-second timeslip at the strip, and those questions regarding power output were enough to convince us a few tests were in order.
It wouldn't only be a question of power and torque with the different intake manifold, but also one of driveability and the fun factor on the average street cruise. Would we lose torque in trade for power? Would it hurt us at the strip? Would it make the car a dog to drive on the street? These are all questions we hoped to answer, and some of them were solved in the first part of the story. This month, we'll cover the intake-manifold install and dyno test. Next month, we'll throw a steeper gear at the Cobra and let it all hang out. We're tempted to run it again with the 3.55s and the new intake, so we'll see if we can squeeze that in.
Accufab has a throttle body...
Accufab has a throttle body for every application. For our test, we chose this 80mm unit with a blank EGR spacer.
Your author had been considering the Trick Flow R manifold, but apples to apples, the Trick Flow Track Heat we were already using was comparable to the Edelbrock Performer RPM II intake suggested by Rick Anderson. The R manifold is said to work best between 2,500 and 7,250 rpm, whereas the Track Heat and RPM II are both suited for 1,500-6,500 rpm. With our 347 making peak power at 5,800 or so, it seemed the Edel-brock piece was the way to go if there was any power left on the table. Anderson agreed and noted that the Trick Flow R seemed to work best on larger 393-408ci motors.
After that assessment--and seeing that Edelbrock was offering a black powdercoated finish that would match our engine-bay theme--we ordered an Edelbrock Performer RPM II intake manifold (PN 71233). It retails for around $820, with the silver finish being a little cheaper and the polished version requiring a bit more bacon.