Muscle Mustangs & Fast Fords
Yo Ken! - March 2014
Answering Your Technical Questions
Too Many Choices
I have been itching to upgrade the power on my bone-stock (it still has the intake silencer) '91 5.0L AOD convertible. The last push came when my wife drove the Mustang and commented, "The van is faster, isn't it?"
I'm starting to accumulate parts, but I'm a little confused about the front (MAF) and back (exhaust) ends of my project. My plan includes a FRPP cast Cobra intake, Trick Flow Specialties 170cc heads, a camshaft and rockers (yet to be determined), and shorty headers. I'll also be changing the 2.73 rear gears to 3.55s.
There is a lot of confusing and contradictory info out there on the MAF and computer. I have a salvage Ford 70mm MAF housing (since it fits my stock airbox and K&N panel filter) to install, but I'm wondering, should I remove the vane connecting the sample tube for better flow? And should I use my old sensor on this new housing? Would I benefit from 24- lb/hr injectors? And if so, how does that affect the MAF and computer?
On the exhaust end, while I wouldn't mind some more growl, I don't want drone. The OEM mufflers are near death, but I understand their size difference was Ford's answer to drone. Where should I concentrate my exhaust efforts? With unequal shorties, how much of a choke is the rest of the system? Should I go high-flow cats, different mid-pipe, bigger pipes, all of the above? Am I wasting my front-end efforts if I keep the OEM exhaust with the shorties?
Ralph, the upgrades you planned will work great together. When it comes to the 70mm mass airflow housing, it must be tuned to the injector size you choose. You cannot remove any components from the housing. Your best bet would be to contact BBK Performance.
A complete exhaust with an X-style mid-pipe and high-flow cats will give a gain in performance and sound, but getting the drone out might be tough. As you know, the factory exhaust was designed to have no drone and good performance. There are many aftermarket exhaust systems that offer a no-drone muffler—DynoMax VT is just one example that controls drone.
The factory exhaust manifolds work well. Aftermarket headers in your application will give you minimal gain in power, and might be best spent elsewhere.
Tires and Tribulations
I have an '08 Stage 3 Roush that I've had modified and re-tuned by JPC. The re-tune, done in mid-August, netted about 433 rwhp and 415 lb-ft of torque. After a recent track outing with the new setup, I found that I'm having issues keeping the wheels from spinning in First and most of the way through Second.
I know some of this is likely driver technique, but I've decided to look into a pair of drag wheels and tires. The problem is that I have no clue where to start. Should I go for a set of 18s and lower profile DOT slicks to match what's on the car? Or should I go for a set of 15s and taller tires to get more sidewall flex? If I go down to the 15s, what wheels will clear the brake and suspension components? Also, I need recommendations on a good set of DOT slicks.
John, I suggest you go with the 18s. For the horsepower you are making, 18s will work just fine. Nitto NT05R Drag Radial and Mickey Thompson ET Street Radial come in 18-inch sizes, and work great at the strip. The Mickeys have a taller sidewall, but are also taller overall, so you will lose some gearing. I have had great luck with NT05R, 285/40-18, and they're very close to the stock rollout, keeping the gearing the same.
In The Hood
I'm the new owner of a '94 Mustang. It has a 306 with Trick Flow Specialties aluminum heads and an F303 cam. Should I be concerned with lowering the temps in the engine bay? I have a Cobra hood with the two snorkel-looking humps, but no airflow through those. Has anyone drilled holes in the black snorkel-looking scoops? Or is a cowl hood better?
Via the Internet
Jared, drilling holes in the Cobra hoodscoops will not measurably lower engine temperatures. The cowl hood would lower temps by extracting heat from under the hood at low speeds, but once your Mustang is at speed, the high pressure at the base of your windshield will force more air in than out. A cold-air kit would be more effective by piping in cooler air to the engine.
Superchargers vs. Nitrous
Superchargers create more pressure in cylinders, and therefore create more engine power. Nitrous creates more pressure in cylinders, and therefore creates more engine power. Superchargers are expensive, drain power from the engine up to a certain rpm, and lower your mpg. Nitrous turns on when you want it; it's cheap, and no mpg problems. For a daily driven '07 GT and an infrequent racer, doesn't it make sense to do nitrous—or am I missing something?
Johnson City, Tennessee
Jim, you are correct, nitrous is less expensive and will not affect your mpg until you use it. For someone who only wants to use the extra power for a weekend at the races, or even just some spirited driving, it does make sense. However, if you want the power on demand without having to worry if the bottle is filled, the charger is the way to go. Supercharging does not cost you mpg if you drive mildly—only when you get into the boost.