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Boost Horsepower with Bolt-on Upgrades

Ever since the first “Fronty” cylinder head appeared on a Model T, there has been a constant demand for add-on items to boost horsepower.

Whether it was to soup up or spiff up, hot rodders were looking for products that gave them a performance edge over factory stock.

For some traditional rodders, a trio of two-barrel carburetors floating on top of a Flathead is as enticing as an ice cream sundae on a hot day.

For others, the “roar” of open lake pipes or the “thumpa-thumpa” rhythm of a high lift cam is the music of high-performance.

Car manufacturers responded to the call for horsepower, eventually building hot rods virtually off the assembly line.

The trend began with Chevy’s historic 327 V-8 in the mid-1950s, the first mass-produced engine to produce one horsepower for every cubic inch.

From that historic milestone in engine development, car makers moved on to the tire-scorching days of the muscle car, turning out bone-stock models that look like they could take off like a space rocket.

Today, through the use of lightweight materials, computers and electronics, car manufacturers are capable of wringing more horsepower out of a cubic-inch than ever before. Advertised horsepower ratings of contemporary engines easily dwarf what a speed shop could coax out of small block Chevy decades ago.

Even so, for those who appreciate high performance, it isn’t enough. Modern technology aside, the hot rod tradition of reaching for even more horsepower continues, according to industry retailers, with a demand for bolt-on improvements over a broader spectrum of manufacturers than ever before. Some standard-bearers among engine makers still set the pace.

“The most popular engine buildout today is GM’s LS engine because it has phenomenal power and great fuel economy,” said Patrick Burris of Royal Purple in Porter, Texas.

But the reliable General has more competition in the performance market than ever before, as manufacturers across the board offer high-tech engines that appeal to enthusiasts.

“The performance aftermarket is expanding to more late-model stuff that is more reliable,” said John Menzler of Comp Cams in Phoenix, Arizona.

Upgraded engine designs from every corner of Detroit, from three-valve Fords to the Chrysler Hemi, are increasing their popularity among customers looking for performance, he noted.

As a result, “there are many high-performance options on the market that weren’t available even three years ago,” said Menzler. “You can change manifolds, the size of the throttle mechanism or to go lightweight rocker arms,” he noted, citing just a few of the bolt-in models that have recently been introduced for these engines.

“This is still a healthy market with strong sales,” said Jeff Calkins of Speedway Motors in Lincoln, Nebraska, who noted that race-minded guys are still inclined to adapt engines to their own individual tastes. “The small block Chevy is still the most commonly used engine in the street rod market, but our customers are also requesting more parts and accessories for vintage engines, such as Flathead Ford V-8s, Chevy six-cylinders, Buick Nailheads and early Chrysler Hemis.” 

Tradition Over Technology

Manufacturers create stratospheric levels of horsepower with technology that seems like it came out of a space-age laboratory. The list of technological advances, necessary to meet fuel economy and emission standards while boosting horsepower, reads like a Mr. Wizard science project.

Fuel injection, variable valve timing, variable cubic-inch displacement, and electronic ignition, are as common on modern power plants as a hand-crank on a Model T.

Besides creating power, they increase reliability and make 100,000-mile spark plug changes routine.

But technology can have a limited appeal for some. Despite the advantages of new technology, many aftermarket customers want parts they can fix with a screwdriver. For these customers, tradition is winning out over technology.

“Interestingly, we are selling more intakes to convert away from EFI,” said Calkins. “Not all of our customers are comfortable tuning their hot rod with a laptop.”

Some of that reluctance to embrace electronic fuel injection may be based on tradition, a strong influence among hot rodders who grew up in the sport proud of their ability to synchronize multiple carburetors. Whether customers are looking for so-called "simple technology," like carburetors or something more advanced such as fuel injection, reflects generational attitudes toward technology in general.

Younger customers who came of age with computers generally are more comfortable with technology.

Older customers, who grew up with hi-fi stereos and dial telephones, may not be as eager to embrace it.  

"A lot of our customers are older guys, and not everybody likes electronic fuel injection," noted Smitty Smith, technical sales manager for Edelbrock in Torrance, California.

That does not mean, however, that customers have to give up on all the advancements of modern engine design. Many manufacturers offer high-flow carburetors, in a range of 650 to 800 CFM, and manifolds compatible with contemporary EFI ignition systems, essentially marrying two generations of technology in one application.

“The demand is still very high for the typical four-barrel muscle car and vintage three-bolt carbs, such as those used on Flathead Fords,” said Calkins, noting that the quality of new models has increased dramatically in the last five years, making them more durable and easier to keep in tune. Some customers are applying this retro attitude to cylinder heads as well, installing older-style heads on newer engines.

“Most cylinder heads fit on later-model engines because they are the same V-8 design,” noted Menzler of Comp Cams. “A lot of customers are putting aluminum retro-fit heads on Pontiacs and Nailhead Buicks.”

Coupled with carburetors and updated intake manifolds, they provide modern- day levels of horsepower without the complications of electronics. But whether customers rely on older technology or new, what they are looking for is as old and traditional as dry lake bed racing.

“We get a lot of calls for headers, intake manifolds, induction ignition and exhaust headers,” said Calkins. “The formula for coaxing more horsepower is more lung power. More air in, more air out, with a hot spark in between.”

Edelbrock’s Smith noted that the most performance gains can be found by matching several components in a single system rather than replacing them individually. By combining a cam, intake manifold, headers and cylinder heads, these “top end” kits offer nine different horsepower levels to match the needs of a wide range of customers. They are especially popular with customers who add them to new crate engines, said Smith, such as the 4.6-liter, three-valve Ford, which is one of his hottest selling new offerings. Most of these systems can generate more than 500 horsepower, with either fuel injection or carburetors-- more than enough for most street applications.

“It eliminates a lot of guesswork and gives the customer the full benefit of the money he is spending,” said Smith. Some retailers also are seeing an uptick in demand for aftermarket superchargers, especially to boost horsepower in stock 2005 and newer Mustangs and the venerable 350 cubic-inch Chevy. Models are available for both EFI and carbureted applications. Their low-profile design, including intake manifolds, easily fits under the stock hood without modifications, turning stock-looking machines into “street sleepers” with more power than meets the eye.  

Sounds Like Performance

Some customers, however, want their horsepower to be noticed.

One of the most popular aftermarket bolt-ins for them is a high lift cam. Although many traditionalists rely on hydraulic flat tappet cams, most retailers report an increasing interest in solid lifter rollers.

Customers who prefer flat tappet cams need patience, since those models require a break-in period for the first 3,000 miles or so. Solid lifter cams, on the other hand, offer an easy break-in period and generally are more durable.

“We switch a lot to rollers,” noted Smith, especially for customers with the popular small block Fords and LT1 Chevy.

Unquestionably, high lift cams lift horsepower. Many retailers estimated a cam switch alone without other modifications can add 25 horsepower because the high lift of the cam reduces friction. That also increases torque for acceleration.

But aside from the performance gains, many customers value the benefits of a high lift cam that is under 10 miles per hour. They may appreciate the big horsepower boost at the drag strip or a back country road, but many retailers conceded that customers who buy high lift cams also are looking for attention at the drive-in as well.

The “thumpa, thumpa” roughness of a high lift cam at idle is just as valuable as performance at the other end of the tachometer.

“There are more opportunities to change the performance and the sound of a vehicle, and that can make newer engines sound like a hot rod with an older engine,” explained Menzler.

He acknowledged that most of his cam upgrades are for sound, echoing the comments of many others.

“Nobody wants to go to the Sonic drive-in sounding like a stock machine,” he said.

But besides “thumpa thumpa,” the rumble of a throaty exhaust is another sound that makes a hot rod stand out from the crowd.

“Street rodders know that a good exhaust system not only improves performance, but will also produce that classic hot rod sound,” noted Calkins.

There are dozens of exhaust systems on the market, in part because there is no universal one size that fits all cars or even all engines, from a single manufacturer. For traditional hot rodders, the biggest concern is what will fit on the car. Narrow spaces between frame rails, for example, can limit options. An exhaust system that has to bend over, around and through the chassis like an obstacle course to clear the transmission or suspension will likely choke up.

“Customers can be very particular about header and muffler selection,” noted Calkins. “On early street rods where space is an issue, finding the right size and shape of header and muffler is especially critical,” he added, to ensure the most resistance-free flow of air.         

Adding a ceramic coating is also popular on headers to insure that the heat stays inside the exhaust system instead of radiating out to other parts of the car, which can cause bodywork or the interior to overheat. 

For traditional hot rod customers, environmental issues and pollution control equipment are usually not a concern, since the vehicles pre-date anti-smog rules or are old enough to be exempted from regular emissions inspections.

Headers, mufflers and full exhaust systems are also widely available for newer, high-tech engines ranging from the Chrysler’s  Hemi,  GM’s LT1 and Ford’s tri-valve models and are especially popular with customers that are either hopping up a stock new model or stuffing a new crate motor into another car.

All of these exhaust systems provide a distinctive warble that announces the extra horsepower they produce. But environmental controls are also a critical issue to address with these aftermarket items.

Newer cars, as well as late-model engines that are stuffed into older-model cars, are subject to emission standards and are factory-equipped with pollution control equipment. That can range from computer-run ignition and fuel systems to catalytic converters and pre-catalysts. Emissions laws require that any exhaust system installed on newer-model hot rods, such as the Mustang or Charger, be compatible with pollution control equipment.

Some products come with disclaimers advising customers that they may not be legal for all street applications. But most manufacturers, working through the Specialty Equipment Market Association (SEMA) and the Environmental Protection Agency (EPA), have certified aftermarket exhaust systems for street-legal use. 

These systems hook up to existing pollutions control devices and are labeled “50-state legal” to remove any doubt of their legitimacy. Because they are a critical part of the combustion process, cylinder heads fall into this category as well and popular modifications for late-model cars also are labeled if they are emissions-legal.            

Smaller Steps to Boost Horsepower

Although major bolt-on items, such as cylinder heads and exhaust systems, are basic methods of increasing horsepower, there are smaller and less expensive ways to subtly boost power as well.

As hot rodders increase their use of bolt-on components to increase horsepower, such as bigger water pumps and more powerful electrical systems, they are adding systems that also draw some of that power to sustain themselves. That has increased the demand for more efficient pulleys and belts. Serpentine belts simplify installation and save space on the engine by consolidating many belts into one. They also increase horsepower by increasing the efficiency of those systems.

“Serpentine belts are better because they reduce slippage,” explained Roy Pigford of March Performance in Naples, Florida. The company manufactures pulleys for a wide range of engines from the mid-1980s to modern models. “They can add 12 to 15 horsepower,” he said.      

A serpentine belt and pulley system also saves space on popular 4.6-liter Fords and LT1 Chevys since it also serves as the harmonic balancer on those engines. There is also an increasing demand for under drive pulleys to reduce the amount of power that these support systems draw off the engine.

“You gain horsepower by slowing down the rpm of the accessories,” said Pigford. He cautioned, however, that there are trade-offs, such as losing battery charge or warmer engine temperatures at high RPMs. In addition to developing belt and pulley systems for most engine combinations, March Performance has recently added two new systems for engines that are popular but overlooked.

“We have new serpentine systems for the Chevy 409 and the Ford Flathead,” he said. “Once we covered applications for most older muscle cars, we had time to develop a product for uncommon applications that are still very popular. We finally caught up to the things we were getting more and more requests for at shows.”       

If intake manifolds and exhaust systems boost horsepower by pushing larger volumes of air through an engine, it sounds reasonable that improved air filters can contribute their fair share to that effort as well. Filters do more than simply collect dust and other contaminants before they can get sucked into the engine. They also can direct air flow by their design and can reduce resistance better than the paper construction that makes up less expensive, over-the-counter filters.

“Every application is different and can make minor to major improvements in horsepower,” said Tim Stewart of K&N Engineering in Riverside, California. A high-performance air filter “allows more dense air into the engine to give it what it needs,” Stewart explained.

Horsepower gains will vary from one engine to another, depending on how efficient it is to begin with. But flow bench tests of his filters on a modern EFI Ford showed a nine horsepower gain, Stewart noted. Because friction robs horsepower, it is believed by some that the use of superior oils can slightly improve horsepower. Synthetic oils are especially well-suited to high temperatures and horsepower of modern EFI powerplants.

“The majority of manufacturers today recommend the use of synthetics because they last longer and improve fuel economy,” said Burris of Royal Purple.

As long as they include high-quality additives, synthetic fuels are a good match for the roller cams and harder metals used in the valve trains of modern, high-tech engines. With high film strength, they are more prone to stay in contact with internal engine parts under the stress of higher temperatures.

“We are seeing people switching to synthetics,” said Burris. “Most of the time, people who are spending a lot of money on their vehicle will buy quality oil.” The more efficient the engine is to begin with, the harder it is to find horsepower gains strictly by using synthetics, he added.

Even so, a one to three percent gain in horsepower and a one to five percent increase in fuel economy are reasonable to expect for most applications.

“It’s not a huge increase in horsepower,” he admitted, but switching to synthetics, especially for high-tech new engines, “is a process you have to go through anyway.” Whether customers are looking for a slight increase or a major gain in horsepower, there are many options available to them to take their vehicles from showroom-stock to a more personalized performance machine.