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Image from Hot Rod Magazine
Of the elements that make up the four-stroke cycle, the exhaust is the last part of the equation, and it also represents the end of an engine's ability to make power. Once the exhaust gas leaves the combustion chamber, it's the exhaust system's job to make sure it gets out fast and stays out. That's why headers, decent-sized exhaust pipes and good mufflers are necessary on high-performance vehicles to get the garbage out and make room for more power. But at what point are headers needed? When are a stock single exhaust and factory muffler choking the engine, inhibiting horsepower? That's what we intend to show here.

To test the effectiveness of equipment that allows better exhalation, we hooked an engine up to Flowmaster's state-of-the-art dyno and tested it with various exhaust systems. We started with stock, cast-iron manifolds, wimpy 2-inch exhaust pipes and stock mufflers, and ended up with a high performance system using headers and unrestrictive mufflers. Are there any drawbacks to these systems? Sure, as with anything that improves performance, there may be some compromises, and we'll talk about that as well. But in most cases, the benefits far outweigh the disadvantages.

These changes netted a difference you can actually feel when you floor the pedal. Power increased across the board, with an increase of 14 horsepower at the peak. Torque also improved by 21 lbs-ft, from 333 to 354. But more importantly, the headers lowered the peak torque rpm by 25 So much for the belief that headers only help at higher rpm.

Image from Hot Rod Magazine
An H-pipe, also known as a crossover pipe, connects both sides of a dual exhaust. Theoretically, this equalizes the pressure in the pipe which helps them scavenge the cylinders more efficiently. It also helps get rid of some of the annoying resonance and frequencies that can occur in dual-exhaust system. Kevin McClelland at Flowmaster believes that the crossover pipe should be as close to the engine as possible, and of the same diameter as the rest of the exhaust, we installed the 2½-inch crossover just after of the header collectors. Interestingly, this modification picked up horsepower and torque throughout the powerband, but lost a few lbs-ft the torque peak. It also raised the torque peak 250 rpm. While this test might not seem conclusive, in our experience a crossover pipe is worth it if for no other reason than the decreased resonance or drumming that reaches the inside of the car.

The engine we tested is pretty stock, yet it still saw a 10-percent horsepower gain from headers and performance mufflers. An increase of 24 hp and 22 lbs-ft of torque might not seem so extreme compared to what's available with nitrous oxide, but it's very good for a relatively inexpensive bolt-on. Also, the power gains would have been more dramatic with a higher-performance engine. More compression, cam timing and carburetion make the exhaust side even more important; stuff more air in the motor and it has a harder time getting out. HR

More information from the article...

• Spark Plug Access - Headers often make it tougher to get to the spark plugs. Expect plug changes to take about twice the usual length of time, if not more. ACCEL has recently introduced a spark plug designed just for headers that is about ½ inch shorter than other plugs, to more easily clear the tubes.
• Fit - Even the most expensive headers sometimes need massaging with a hammer to fit around steering boxes or scattershields.
• Noise - Tube headers are thinner than iron manifolds, so they’re going to be noisier and hotter.
• Leaks - Headers are notorious for leaking, at both the head flange and the collector. A tip is to use Permatex Ultra Copper silicone on both surfaces, and Loctite on the bolts. Stage 8 fasteners also ensure a good seal, and will fit all but the biggest tube headers. The more expensive headers usually have thicker flanges and tubing, which helps sealing greatly.
• Plug Wire Burning - Headers can also wreak havoc with plug wires. The solutions range from proper routing strategy to using insulated wires or insulating covers.
• Accessory Brackets - Because some accessories, particularly the alternator, A/C compressor, and smog pump, have at least one bolt connected to the head, headers will often require adapters to make this stuff fit.
• Starter Access - There’s a good possibility that once the headers are installed, you won’t be able to get the starter on or off, especially on a small block Ch%*y. Be prepared.
• Legality - Most of the major header manufacturers have Executive Order (E.O.) numbers on their headers, but if smog legality is a concern in your area, you’d better make sure.

Part Numbers

• '61-'71 Truck Small Block 273-360 Hedman Hedders - # 79010
• '61-'71 Truck Small Block 273-360 Mopar Performance Headers - # P4529438
• '64-'70 A-100 Van\Truck Small Block 273-360 Hedman Hedders - #79030
• '61-'71 Truck Big Block 383-440 Hedman Hedders - # 79250**
• `72-`91 Truck Small Block 318-360 Hedman Hedders - # 79080 2WD and # 79170 4WD
• `72-`91 Truck Small Block 318-360 Mopar Performance Headers - #P4529439 2WD and #P4529440 4WD
• `72-`91 Dodge B-series Vans (probably fit`70-`71 as well, but no guarantee here) - #P4529467

{Most} Hedman Hedders are well fitted to the '61-'71 Trucks. The hardest part to installing the headers is removing the old exhaust since parts are usually rusted onto the vehicle. Once installed, the next step is finding a reputable shop to weld the pipes up to the headers and out the back or side of the truck.

For a complete set of headers for your Polysphere engine in a `61-`71 Dodge Truck, call Harold Johnson of Spitfire Headers in Arkansas at (501) 474-0120. Special thanks to Bill Pate for this tidbit of information (Bill says the Headers are a great fit).

Sanderson part number DD1 is recommended for 318-360 small block motors. Part number DD2 (383-440) has a tube size of 1 7/8" and a collector size of 3", according to their catalog. These are the "Block Hugger" type headers. Both sizes of these headers are available in plain steel, Jet Hot coated or polished stainless.

Use Ultra Copper Silicone Sealant. Hot Rod Magazine recommended this in the above article, and the author has never encountered any leaks with the use of this suggestion. Loctite/Permatex makes the product, and it is available at NAPA auto parts as well as most other parts stores. Use this product to accompany the header gaskets or factory exhaust manifold gaskets, not in place of them. The product holds to extreme tempatures, and cleans up easily when removal is desired.

Plan your entire exhaust system. With careful planning and some research, one can achieve maximum horsepower gains with a high quality sound out of the pipes. Here are some suggestions...

• Small-Block engines do best with 2" to 2.5" pipes behind the headers.
• Big-Block Engines output best with at least 2.5" to 3.5" pipes.
• Glass-packs are generally louder than turbo type mufflers. While glass-packs sometimes give a better sound, at higher engine speeds the sound can be too loud or otherwise unbearable. Choosing high flow mufflers can be a little more expensive, but will provide equivalent if not better horsepower and torque gains when compared with glass-packs.
• Stainless steel pipes are exotic, and darn expensive. If you are making a mega buck hauler or want something that will last, buy stainless. Nonetheless, normal steel pipes driven' daily will last an adequate length of time if not neglected.
• Re-check the bolts every once in a while. Due to the extreme tempatures and vibration present in an exhaust system, it is important to keep all fasteners as tight as possible. If neglected, the bolts can loosen and allow the collector and head flanges to warp which will forever ruin the headers.

Please Note: This page is intended as a guide for the project outlined, and is not guaranteed in any way. All info above is to the best knowledge of the author.