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Mustang GT350 Restomod 3

Adding more power

As mentioned in our initial installment, the Shelby GT350 wasn't named for its engine size, as is typical for many cars. Instead, back in 1965 Carroll Shelby had grown weary in a lengthy meeting about naming the car, so on a whim he abruptly decided to base it on the number of steps between two of his shops.

The engine used in the GT350 was a 289 cubic inch Ford V-8, the 271 Hi-Po version. Its output was upped on the Shelby GT350 to 306 hp with a Holley 715cfm carburetor bolted on an aluminum Cobra hi-rise manifold. Nothing else on the 271 Hi-Po was touched.

Ponying Up

By today's standards, those were relatively limited modifications. Thanks to advancements in automotive technology, it's not so difficult to pull a lot more ponies out of a 289 cubic inch V-8, even without modifying the bottom end with a stroker crankshaft or the use of forced induction from a turbo or supercharger. A good rule of thumb for a streetable high-performance engine, however, is about 1.1 hp per cubic inch of displacement. On a 289ci V-8, that would calculate out to 318 hp, not all that much more than the original '65 GT350.

What's more important than a high horsepower number is balancing and integrating the performance components with each other, both on the engine and the vehicle as a whole. We've already touched on the improvements made to the chassis and driveline to handle the increased output, so now we'll cover some aspects of the Edelbrock engine mods used here.

Total Package

To get great performance out of any engine, the components must work together. Since the early 1980's, the Edelbrock Total Power Package System has helped to match performance parts for many street performance enthusiasts. Matching the intake manifold, camshaft, cylinder heads and carburetor are the core of the Power Package concept.

Choosing a particular package depends on your intended use of the vehicle, and tailoring the output to a specific range in the powerband. For instance, on a street-legal car the Performer Power Package is designed for power from idle to 5500 rpm-good for stoplight starts and general driving. This package increases performance and driveability in the low to mid-rpm range, ideal for passing, towing, climbing grades and daily driving.

On a car that sees occasional duty on a roadcourse, such as the Mustang shown here, acceleration off the line is not as important as a strong pull out of a curve. For that application, the Performer RPM Power Package focuses on increasing power from 1500 to 6500 rpm. It still offers a broad operating range for streetable performance, but with more mid and high-end horsepower. The dual-plane design of the Performer RPM intake works with an Edelbrock carburetor for more throttle response and power up to 6500 rpm. The Performer RPM camshaft has more lift and duration than most street cams with acceptable low-end torque (10"-12" Hg @ idle). Going even further up the powerband is the Torker II, designed for power in the 2500 to 6500 rpm (especially for engines with a low hood clearance).

In looking at these three packages, what's important to keep in mind is that performance parts must be mated in a concerted fashion for a particular performance goal. No single set of components can do all things really well.

Cool Down

With an increase in power come other consequences, though. A hotter engine runs, well, hotter, and may need a more efficient cooling system with an aluminum radiator and perhaps an electric puller fan as well. More power means more loads on the chassis, so bracing in the engine bay may be in order. While you're at it, a roll cage behind the front seats is a good to add as well, in part because it stiffens up the frame, aside from the improved safety aspect.

Speaking of safety, you'll need a safety harness with shoulder straps instead of the standard seatbelt arrangement. Bolstered seats are a good addition as well to keep you snugly in place in tight turn. A fire extinguisher in a handy location makes good sense, too.

So looking at this Mustang as a whole, it's clear there are a wide range of mods that can be done to improve its performance and safety on both the street and the track. In our final installment, we'll get into the exhaust system, from the ceramic-coated headers to the cutouts for off-road use to the high-flow mufflers.