Exhaust System Guide for Restoring Your Mustang

If your original fuel tank is in decent condition, you can simply clean it and then refinish it with a suitable coating, such as Eastwood’s Tank Tone (see sample can on tank) to maintain an OEM appearance. (For tanks with more than surface rust damage, follow the procedures described in Chapter 3 to repair the damage before painting.) Fuel tanks that are too heavily damaged are best replaced with a high-quality replacement such as the one shown here. This tank has not yet been coated with Tank Tone, though it came painted to prevent rust.

Those concerned about safety might want to consider installing a fuel cell instead of a regular fuel tank. Early Mustangs are vulnerable to fuel entering the passenger compartment in a severe rear-end collision because the OEM tank is in the trunk and not isolated by another panel. A fuel cell minimizes fuel slosh under heavy braking or turning greatly reduces the chance of fuel spilling into the passenger compartment in a crash. Fuel cells are not terribly expensive, and there are specific, drop-in models made for most early Mustangs.

A standard mechanical fuel pump is usually more than sufficient for a carbureted car that will be driven lightly. If the fuel pump isn’t working properly, replace it. If more flow is needed for a higheroutput engine, there are higher flow mechanical units and electric pumps available. The latter are usually mounted below the fuel tank at the rear of the car. Some electric pumps are meant for racing use only and shouldn’t be used on most streetdriven vehicles. For cars that will be driven often and/or in inclement weather, an electric pump is ideal for such work.

Carburetor choice has a significant impact on the performance and drivability of the car. If you want to remain authentic, then either rebuild the stock carb or buy a direct replacement from a company such as Pony Carburetors, which specializes in early-Mustang applications. In many cases, a non-standard Autolite carb can provide better performance while still retaining a factory look. This Autolite 4100 series carb wasn’t the stock carb for the 1968 GT, but it should provide better performance with the modifications we’ve made. Note the inline fuel filter to prevent dirt from entering the carb. Always use some form of inline filter between the pump and the carb. There are also many aftermarket performance carbs that may be a better choice with a more modified engine, but they do not usually retain the factory look.

If your engine has been modified, a high-performance openelement- style air cleaner, like the one shown here, provides increased airflow and hence performance. These came standard on many factory high-performance models. While not as good a solution as a sealed ram-air/cold-air system, they are much less restrictive than a regular snorkel style air cleaner housing—plus they look a whole lot better. In some cases, you can also use a taller filter element to reduce flow restriction, at least until hood clearance becomes an issue.

These factory high performance, Classic Auto Supply K-code exhaust manifolds are significantly less restrictive than the standard log-type manifolds, yet they are also much more durable than headers. Headers usually make more power, but they are also noisier and pose problems with fit and appearance if you want to keep a stock look. You also need to make downstream changes. These manifolds would be fine for the power level we were at, plus they looked OEM and kept the noise level down. We coated them with Eastwood’s Factory Gray High Temp Coating Spray to retain their cast-iron color and prevent rust.

Using the K-code exhaust manifolds required a little change in the H-pipe because the exit of these manifolds is not in the same place as on the standard manifolds. Luckily National Parts Depot (NPD) had just the part we needed in stock. The 1967 289 K-code option used this pipe, which would work just fine on our 1968 (same body style) with a 302 (same external engine dimensions). The NPD piece is an exact duplicate of the factory part, right down to the flanges and type of exhaust seals (“donuts”) used. With a higher-performance application, you may want to use larger-diameter tubing that’s been custom mandrel bent to provide even less restriction.

NPD also offers a complete exhaust kit for our 1968 Fastback, as it does for virtually all early Mustangs. The kit included precision bent tubes that are a direct fit along with the correct type of mufflers and factory-style hangers and hardware. We chose slightly different quad-style exhaust tips (shown), which resemble a style offered by the factory. While this system is perfect for moderate performance levels, a larger-diameter system with mandrel bends and less-restrictive mufflers would likely be a better choice for a higher-output engine where noise is less of a concern.

This view shows what a typical true dual exhaust system looks like when it is installed on the vehicle. This particular car was a convertible and had the extra underbody bracing for the pipes to clear. The H-pipe was also a more traditional design than our K-code version, plus the mufflers are aftermarket units, which have a more aggressive tone than our stock replacement-style parts. This system has welded joints instead of using clamps to minimize the potential for exhaust leaks or the parts coming apart.

One trick to consider on cars that have GT-style exhaust trumpets is to have hidden exhaust outlets behind the rear valence panel instead of keeping the OEM trumpets functional. The OEM trumpets look great, but they tend to get dirty from the exhaust very quickly. They also restrict exhaust flow, a compromise we didn’t want to make. Using dummy trumpets to keep that particular look, while having the real exhaust outlets hidden, keeps the trumpets clean and also improves performance.