Build With Bolt-On Horsepower, But Proceed With Caution - Engine Builder Magazine

Build With Bolt-On Horsepower, But Proceed With Caution

Whether the speed equipment is old school hardware or electronic in nature, you can be sure it is designed to turn automobile engines into more efficient air pumps.

“Because the engine really is an air pump, I tell my customers one of the biggest things they can do is bolt on a different exhaust system,” says Dick Casar of Done Rite Automotive Performance in  ( Typically headers and dual exhausts will be installed on classic muscle cars, while newer cars will benefit from a 52-states-legal cat-back (catalytic converter back) exhaust system. Most cat-back systems are legal in all states.

Aftermarket headers are designed to give burnt gases exiting the engine a smoother flow route compared to factory-installed exhaust manifolds. Tight tuck models are available for cramped engine compartments. A long tube header kit with a two-inch diameter primary pipe and a pair of catalytic converters can run $1,000 to $2,000 (note: prices quoted in this article are ballpark prices at the counter with your markup).

Brand name systems are usually designed for direct fits on specific cars and can add 8 to 10 hp. Stainless steel hardware will eliminate rust, but mild steel hardware is stronger; your choice. Look for kits that have exhaust manifold studs with hexes on the end for easy installation with an Allen wrench. Before ordering your studs, double check how long you need them to be.

For about $400-$500 a performance style free-flowing exhaust system will include fat mandrel-bent pipes (usually 2-1/2-in. diameter) and low-restriction type mufflers for an increase of 15 to 20 hp. Due to emissions regulations, modern cars need to go with the cat-back option, which will give boosts in the 11-15 hp range for $1,200 to $1,500.

The critical fuel/air mixture that feeds the “air pump” its proper diet is another area where improvements can be made today, says Casar. “On your older carbureted cars, look for gains in the eight horsepower range after adding an aftermarket performance carburetor that will flow 650 cubic feet of air per minute through the engine. Or you can add bigger jets and get the carburetor pumping up to 750 cfm of air for roughly a 10-hp gain.”

According to Ed Casar – Dick’s son and partner at Done Rite Automotive Performance – carburetor companies haven’t been sleeping. Recently, they came out with models that incorporate new ways to atomize fuel. “They look the same as the old double pumper, but lasers are used to drill smaller holes and the manufacturers also have more surface control today.”

Ed continues, “Thanks to the air/fuel meters we have now, we can take a carbureted car, put it on our Super Flow dyno and tune the thing the same way we tune fuel-injection equipped cars. The only difference is we have to install parts instead of pushing computer keys.”

Ed’s dad puts the addition of a cold air inlet second on his personal list of bolt-on items that boost horsepower. This is another term for special, performance type mass airflow sensors with calibration improvements that put more cold air into the engine and enhance response to his customer’s foot pressing on the accelerator. These list for around $300 and add about 12 ponies.

The use of low-restriction air cleaners for improved performance probably dates back to the early days of hot rodding. Imported sports cars of the early ’50s had them as standard equipment. When we got our first car (a ’55 Chevy) in 1965, we could hardly wait to order a chrome, paper filter air cleaner from the J.C. Whitney catalog. Today many customers say the hot ticket is the K & N filter that they can get at any store from Wal-Mart to NAPA. They look good, sound great and cost around $50 average for most cars. Customers shouldn’t expect much more than one horsepower increase, however.

If you want to bolt on some old school horsepower by upgrading your distributor, the traditional makers of high-performance sparkers are getting a bit creative these days. Dick Casar points out that MSD has come up with a distributor that looks like something from days gone by, but has electronics inside it. “Actually, it has the same electronics that they use in the fuel-injected version,” he explained.

“With fuel injection you have a base fuel map that tells you how much your injectors are spraying and you have another map that tells you what your timing is at different points in time," Casar says. "So, now we have electronic distributors that look the same as mechanical ones on the outside, but we can actually plug our laptop into them and tune like we do to a fuel-injected car. We can actually put a fuel map in there to get proper timing over the complete spectrum.”

Aftermarket intakes for carbureted and throttle body-injected cars have smoother, better-designed internal passages that aid the flow of air into the engine. Their size, material make up and shape also boost engine performance when they allow more air into an engine. A gain of 10 hp can be expected.

Speaking of throttle bodies, performance improvements are available to help TBI systems flow more air into an engine. Among the products offered today are higher-flow TBI power plates, ported throttle bodies, adjustable fuel pressure regulators, fuel pressure gauge adapters and spacers. You can figure on charging at least $400 for a good bolt-on throttle body with a gain of 15 hp.

What about the new self-tuning electronic fuel-injection systems? “Once you install a F.A.S.T. system or the new Holley system, you don’t have to do much on tuning,” says Dick Casar. “They started the self-tuning systems about 10 years ago and the early ones were feedback systems that used to really hunt around, but now they actually grab a number and automatically interpolate it and change the numbers around it. So, all you have to do is drive it through your rpm range and if you’re still driving, it’s still tweaking. The more it gets tweaked, the more you get everything dialed in.”

For around $400, a performance programmer can help the computer function better with other bolt-on horsepower items. Something like the DiabloSport Predator flash programmer will give a boost of about 12 hp. “You may see gas mileage go up too,” said Dick Casar. “Back in the old days people would say that if you’re doing this or that for performance, that you’re going to hurt your fuel mileage, but nowadays it usually helps it. We put stuff on an older Corvette along with a supercharger to make it more efficient and the customer came back to tell us he was getting 34 mpg at 80 mph.”

You can also recommend your customer upgrade the car or truck’s computer (if it has one) with a performance chip, but that will only add about two horsepower.

On the other hand, a centrifugal supercharger (about $3,200) will add as much as 120 ponies after it’s bolted on the engine. “The problem is a customer comes in and thinks it would be cool to supercharge his engine, but he doesn’t realize that there are different styles of superchargers,” Dick Casar explained. “There’s the centrifugal type like a Vortec and the screw-in type like a Magna or Dana and you have to know the application that he’s using it for.”

According to Dick, the centrifugal supercharger doesn’t start pumping a good quantity of air into the engine until you get the rpm up. In contrast, a screw type or Roots type supercharger will work right off idle and push you back in your seat at three-quarters throttle. “You can’t say one is better, because it depends on the application,” Ed Casar points out. “If you’re building the engine for drag racing, a centrifugal supercharger is great because the more they crank it up, the more air pressure they’ll get, but the screw type is what you want for pulling and hauling heavy loads and so on. Unfortunately, people think a supercharger is a supercharger and they’ll often put on the wrong type because it’s $1,000 cheaper.”

Ed’s dad also pointed out that superchargers are well suited for modern engines with their 8.5:1 compression ratios, but aren’t made for older V8s with 10.0:1 compression. “If you’re putting an engine together and put 10.0:1 pistons in there and then bolt a supercharger on, you can run into detonation problems,” Dick warns. “And then you can’t give it a lot of timing and you can only give them three pounds of boost, so you cut the boost way back.”

Dick says the new kits, like a Magna kit, come with everything an engine builder needs, including complete instructions that should be followed. “If it’s done right, we’ll put these on in the shop and never see the car again,” he said. “You’re not going to get that long-distance call from a customer who’s broken down in the middle of Idaho.” The install involves unbolting the intake manifold. “The kits come with their own intake manifold and intercooler,” Dick stresses. “They are well fabricated pieces, not universal fit parts where belts come off.”

The install does not involve doing anything to the engine. The supercharger mounts on the engine as if you were mounting an alternator. You attach the belt and run a pipe over to the engine’s air inlet. “Since you’re changing the intake and adding plumbing, there are a lot more parts,” Dick said. “That’s why the screw-type superchargers cost more, but they are what most enthusiasts really want for better highway performance. They should just make sure they fit under the hood, but newer designs can fit under a Corvette’s hood with an inch to spare. Some models for newer cars now mount low in the valley.”

Done Rite Automotive Performance doesn’t do nitrous oxide systems, but Dick thinks they work well for drag racing. “Nitrous gives you power that you don’t have to apply power to get, because you don’t need to rob horsepower to spin anything,” he notes. “They say it’s cheap horsepower, but if you drive it everyday for street use, you have to keep getting that bottle filled up compared to a supercharger, where it’s in there all the time. Still, people who may want to get to 300 hp for $500 bucks will use nitro and realize gains of more than 100 to 200 hp.”

Few enthusiasts think of gaining horsepower with cooling improvements, but replacing the mechanical water pump with a bolt-on electric pump can actually net you about 25 hp for $600 or so. At the same time you’re gaining ponies, you’ll be protecting the customer’s engine by achieving lower operating temperature.

Underdrive pulleys are another way to bolt on up to 25 hp. Changing pulleys will reduce belt drag and spin a turbocharger or supercharger faster, so that it pumps more air into the engine. A serpentine belt conversion kit with underdrive pulleys for the crank, alternator and pumps can run  $500, but be very careful that such a set up will work with other changes you make.

“Enthusiasts may find that they can change pulleys and spin that thing faster (more boost), so they can go one up on their buddies. They take a system that was safe for eight pounds of boost and then run up to 13 pounds,” Dick Casar warns. “At that point, the internal parts cannot take that and they’ll wind up bending rods and breaking pistons because you didn’t beef up the internals.”

Which leads us into the second part of our story about what kinds of things need to be done internally when enthusiasts bolt on horsepower. However, before we go there, let’s first talk about rocker arms, cylinder heads and cams. Since bolting on these items leads you to opening up the engine, you can also beef the internals up while you have things apart.

“The heads are the next stage,” Dick Casar points out. “They want to put on heads that flow air through the engine better. Gains of up to 70 hp can be achieved by getting rid of the old cast iron factory heads and bolting on aluminum heads with larger intake runners, combustion chambers and valves.” The cost of this will start at about $1,300 and go almost as high as the market can bear for a set of really exotic racing heads. You can even get high-tech performance heads for classic engines like the early 1950s Oldsmobile Rocket 88 from suppliers.

“When they take the heads off the engine, they’ll also pull the camshaft out and stick a different one with a performance grind in,” notes Ed Casar. The addition of other valve train upgrades like roller rocker arms (for about $300) can add about 20 to 22 hp, too. “The problem is,” Ed emphasizes. “They too often leave the bottom end untouched – so the stock pistons and all that stuff start getting iffy. As long as they have gotten this far, what they should really do is remove the engine from the vehicle and, if they’re going to 700 hp with their bolt-ons, they should add internals – rods, bearing and pistons – that will take 700 hp.”

According to Ed, what typically happens is an engine builder will spend a lot on a supercharger kit that fits 13 different vehicles, then want to do more and start mixing and matching pulleys. “Pretty soon, they are starting to put more load on the pistons and the entire rotating assembly,” he explains. “By this time, the tune is no longer right, either. So even if the parts hold up, something else is going to go wrong. Aluminum melts at 1,300 or 1,400 degrees F and if you have a bad mixture adding heat you’ll burn off the top of the pistons. It’s a bad thing to do, but at the same time, it’s an easy thing to do.”

Ed underlines the concept that engine internals have to be done right. “You have to know the limitations of what you’re building and you have to be man enough to realize that if you do the wrong thing, you’re going to wreck the engine’s longevity. What we do is go to the Advanced Engine Technology Conference (AETC) seminars where the manufacturers of products are actually invited to speak So we’ll hear Diamond piston experts speak about pistons for the new modular engines or other techs talking about different engine geometries, and we’ll have custom piston people telling us and showing us the ins-and-outs of their products.”

Ed says these things are really handy to know when you’re trying to build an engine that’s going to have a really highly stressed piston. “You learn that these geometries exist and you’re able to look at an engine and notice that the burnt pistons you see on our bench were actually the wrong application for an engine of a particular boost level,” he explained. “That piston couldn’t live very long because the valves were cut and the piston itself was really, really thin.”

According to Dick Casar, over the years automakers have redesigned combustion chambers for better emissions, so the little bit of space between the top of a piston and the top ring land doesn’t get burned. “That little gap is actually for air/fuel mixture that goes out the exhaust as emissions,” Dick told us. “And they have kept moving the top ring higher to diminish that space as much as possible. That’s good for emissions, but the piston gets thinner with less material there and if you stress things with, say, a supercharger, you start to break those thin edges off. In your new engines, everything is getting smaller.”

Dick says that even the type of oil needed today has changed. “Smaller pistons create less side friction, so piston clearances and tolerances get tighter and they can’t tolerate thicker oil,” he explained. “If you put in more clearance on a performance engine, you actually have to change bearings so you can use a thicker oil that won’t burn up after you bolt on a supercharger or other goodies.”

Head gasket sealing is another concern that Dick and Ed focus on. “If the engine builder doesn’t want to put in lock-wire gaskets, he can use a multi-layer steel gasket. That works very well because head gaskets must transfer heat to stay intact and the multi-layer pack does a good job when it goes through the heat cycle. Copper gaskets are good for racing, but not for the streets today.”

Done Right’s bottom line recommendation is to stick with tried and true hardware and electronics made by name brand manufacturers. “They put it on something to test it and they know exactly what it’s good for,” Dick Casar notes. “If you put it on your engine and don’t change other things that aren’t in the program, you’ll be okay. If you change things, then you’re being a pioneer and the manufacturers won’t support that because it can lead to internal problems.” guy hanson
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