Hot Rods 10 steps to power (long)
-Josh-
09-19-2005, 01:22 PM
I thought this might help some newbies that come in here and ask some questions. Hot Rod is a big source of mine for good technical articles, this i consider pretty basic and a good one indeed for beginners.
10 Steps To Power
Prioritize Your Power From Stock To Stout
By Jeff Smith
Photography: Jeff Smith
Power is what hot rodding is all about. The classic approach is to take a stock or near-stock engine and tweak it until it thumps. But what should you do first? There are literally hundreds of roads to choose from, but a little forethought and planning will create an efficient route that makes more sense than just “throwing parts at it.”
These 10 steps are not cast in stone, and you don’t necessarily have to follow them in the precise order they’re presented here. They are also composed with an eye toward accomplishing the easier aspects first, with the more difficult steps left for when you’ve gained experience.
If there is one point that can’t be overstressed, it’s that testing and tuning can make a huge difference in performance. Each change, such as exhaust, intake manifold, carburetor or ignition, requires retuning to determine optimal jetting and timing for your engine combination. That may sound like a lot of work, and it is. But it is the best and only way to extract maximum power from your engine. Tuning isn’t expensive, but it is time-consuming. So be prepared to spend time tinkering.
Tune up-
Whether your engine is stock or tweaked, a tune-up can unleash lost power. But a good tune-up involves more than just screwing in a set of spark plugs. A high-performance tune-up should include high-quality plugs, points and a condenser (if necessary), a cap, a rotor, plug wires, fuel and air filters and perhaps even a carburetor rebuild kit. Even that lowly two-barrel could stand a rebuild and will respond with better performance.
But don’t just swap parts, do a compression test. Are all the cylinders within 10 percent? If not, a tune-up will not cure its ills. Vacuum leaks are another common source of part-throttle and idle problems. If the idle rpm surges or “hunts,” the idle circuit is either excessively lean or there is a vacuum leak in the intake manifold or in the carburetor. Now is a good time to experiment with initial timing and weaker mechanical-advance springs in the distributor. Also ensure that the vacuum-advance canister is working properly.
Exhaust-
Many hot rodders don’t consider the exhaust system very important, but it’s actually critical to overall performance. That’s why it is the second item on our list. Most factory exhaust systems are designed to be quiet and inexpensive—in that order. Power is usually farther down on the list. In most cases, if your engine is equipped with a single exhaust system, a dual exhaust is the ideal first step to increasing power. For example, a ’72 307 single-exhaust two-barrel Chevelle will still respond favorably to a dual exhaust designed for a 350 SS Chevelle. And the upgrade is probably a bolt-on.
Walker builds dozens of factory-style replacement dual exhaust systems for all kinds of cars. Do a little research at the parts store to determine what’s available for your car. For many late-model cars, catalytic converters prevent you from legally modifying the exhaust ahead of the catalytic converter, unless the components are certified. However, you can legally alter the exhaust after the cat any way you wish. That makes the selection of so-called “cat-back” components important, especially the muffler. Walker, Borla, Flowmaster and others offer many high-performance mufflers that will do the job.
Induction-
Induction is where most enthusiasts start in a hi-po buildup, but a better intake and carburetor will perform only if the exhaust flows properly. Wise choices for induction changes include dual-plane intake manifolds and a conservative carburetor selection. Dual-plane intakes such as Edelbrock’s Performer, Holley’s Contender and Weiand’s Action-Plus will improve torque. That’s what you’ll feel in the seat of your pants. When replacing a two-barrel carburetor, don’t go overboard with carburetion. The Holley 0-1850 600-cfm carburetor will work well on any mild small-block.
But don’t overlook the stock Rochester Quadrajet, FoMoCo or the Mopar Carter-built four-barrels. They are all quality carbs when rebuilt properly and can offer great performance at a low cost. And don’t forget to include a K&N air filter with this swap. The K&N is better than any paper filter, and you can clean and reuse it when it gets dirty.
Fuel Delivery-
You can’t make power with a fuel-starved engine. In most cases, stock mechanical or factory electric fuel pumps are adequate for mild engines (making around 300 horsepower or less). Make sure the entire fuel-delivery system is adequate. We know of several occasions when a killer fuel-delivery system was thwarted by a kinked factory fuel line. Even small 5/16-inch fuel line is sufficient for 300 horsepower. Think about replacing that wimpy inline fuel filter with a high-flow filter.
Headers-
Adding headers at this point should really pump up the performance. While headers are certainly worth power, they will add even more performance when combined with the previously mentioned changes. You could also add headers at the same time as the dual exhaust. When choosing headers, stay conservative. Small-tube headers for a mild small-block will definitely improve low- and midrange torque (where your engine spends most of its time) while still increasing top-end power. For 350ci-or-smaller engines, 1-5/8-inch primary-tube headers are the largest you should use. If 1½-inch tube headers are available, use them, especially for 302- and 305ci engines. This is also a great time to consider adding a crossover or H-pipe to the exhaust system. That will add torque at no expense to top-end power!
Ignition-
Ignition systems are like exhaust systems. They usually don’t create power, but if the ignition is weak or defective, it can definitely cost power. First of all, there’s nothing wrong with a well-maintained, points-type ignition system. Points are only suspect because you must maintain the proper dwell angle, which changes as the rubbing block wears. Also, some cheap, generic points are junk at over 4000 rpm, so always buy quality, name-brand points. Don’t go for a killer coil with a points system because the increased amperage draw will burn the points up prematurely, especially if the engine is idled for long periods.
An important step is to always use a high-quality plug-wire set. We’ve seen an otherwise stout engine fall on its face from a brand-new set of $9.95 plug wires. If the wires are more than five years old, replace them with the spiral-wound wrapped wires from ACCEL, MSD, Jacobs, Moroso or others.
Traction-
Now that your engine is making more power, it’s probably spinning the tires. The best way to solve that is with bigger, wider or stickier tires. M&H and Mickey Thompson both offer soft-compound tires, but they are expensive and obviously don’t last very long. Other choices to improve traction using your existing tires include traction devices such as traction bars for leaf-spring cars. These aren’t crucial unless you have a wheelhop problem. For coil-spring cars, Air Lift makes air bags that allow you to preload the right rear side of the car to aid traction, especially if you have an open differential.
A positraction device is probably the best overall choice for any performance car, simply because it is transparent during the day-to-day operation of the car—yet it aids traction by driving both tires under acceleration. Deeper gear ratios (changing from 3.08 to 3.73:1, for example) will also help acceleration, but you pay the price of excessive rpm on the highway (see the sidebar “At Any Speed”).
Camshaft-
Notice that a bigger camshaft is far down on our list of modifications. That’s because the add-on pieces above are easier to install, and after making those changes, you probably have a solid running car. Again, the key here is to create a matched package of conservative pieces, such as a dual-plane intake, small carb, small headers and an excellent exhaust system. Match that with a conservative camshaft and the engine will respond. Stay with a short-duration, hydraulic, flat-tappet cam that has a little more lift and duration than your stock cam. Also, keep in mind that the cam swap will require new gaskets, and adding a new timing chain and gear is a good idea as well.
Heads-
Most hot rodders can’t afford a trick set of aluminum heads, which is too bad because this is an area where spending a little more money can really pay off. Of course, you still must remain conservative to prevent killing torque, but Edelbrock and Air Flow Research both make emissions-legal small-block Chevy heads that will add serious power. World Products also makes a replacement iron head that flows well. Of course, rebuilding your stock heads is an excellent way to increase power on a budget. But price all this work first. You may find that the machine work and parts add up to almost the same amount as a new set of aluminum heads!
Drivetrain-
Now that you’re making all this power, it’s time to take a closer look at the drivetrain. For automatic-equipped cars, a higher stall-speed torque converter is one way to drop your elapsed time, but you pay the price of “mushy” throttle response. For an everyday street machine, keep the stall speed at 2200 rpm or less.
For manual-transmission street machines, a good shifter is a must. There’s nothing more frustrating than a balky shifter that tends to lock up when you least expect it. An excellent street-clutch combo is the Centerforce matched with the new Dual Friction disc. This combines excellent holding power with soft pedal pressures that make it easy to live with on the street.
Put it all together and you have the makings of an excellent daily-driven street machine. This modular approach allows you to make changes as you can afford them while still enjoying your car along the way.
At any speed-
As you can see by this chart, tire diameter and gear ratio have a dramatic effect on cruise rpm. One way to lessen the high-rpm effect of a deep rear gear like a 4.56 is to use a taller tire for daily driving, then switch to a shorter tire for racing.
This chart assumes zero drivetrain slippage. When using a nonlockup torque converter, these rpm levels would be higher by approximately 200 to 300 rpm or more due to torque-converter slippage.
http://hotrod.com/tipstricks/p108534_image_small.jpg
[/hotrodarticle]
Keep in mind this is the pretty basic of basic modding here. It varies from import and domestic and also the kind of budget, IMO there's a few things that could have been mentioned but this article was mainly for beginners. If anyone wants to have a discussion on this and have INTELLIGENT modification discussions, i'm always open for one. :biggrin:
10 Steps To Power
Prioritize Your Power From Stock To Stout
By Jeff Smith
Photography: Jeff Smith
Power is what hot rodding is all about. The classic approach is to take a stock or near-stock engine and tweak it until it thumps. But what should you do first? There are literally hundreds of roads to choose from, but a little forethought and planning will create an efficient route that makes more sense than just “throwing parts at it.”
These 10 steps are not cast in stone, and you don’t necessarily have to follow them in the precise order they’re presented here. They are also composed with an eye toward accomplishing the easier aspects first, with the more difficult steps left for when you’ve gained experience.
If there is one point that can’t be overstressed, it’s that testing and tuning can make a huge difference in performance. Each change, such as exhaust, intake manifold, carburetor or ignition, requires retuning to determine optimal jetting and timing for your engine combination. That may sound like a lot of work, and it is. But it is the best and only way to extract maximum power from your engine. Tuning isn’t expensive, but it is time-consuming. So be prepared to spend time tinkering.
Tune up-
Whether your engine is stock or tweaked, a tune-up can unleash lost power. But a good tune-up involves more than just screwing in a set of spark plugs. A high-performance tune-up should include high-quality plugs, points and a condenser (if necessary), a cap, a rotor, plug wires, fuel and air filters and perhaps even a carburetor rebuild kit. Even that lowly two-barrel could stand a rebuild and will respond with better performance.
But don’t just swap parts, do a compression test. Are all the cylinders within 10 percent? If not, a tune-up will not cure its ills. Vacuum leaks are another common source of part-throttle and idle problems. If the idle rpm surges or “hunts,” the idle circuit is either excessively lean or there is a vacuum leak in the intake manifold or in the carburetor. Now is a good time to experiment with initial timing and weaker mechanical-advance springs in the distributor. Also ensure that the vacuum-advance canister is working properly.
Exhaust-
Many hot rodders don’t consider the exhaust system very important, but it’s actually critical to overall performance. That’s why it is the second item on our list. Most factory exhaust systems are designed to be quiet and inexpensive—in that order. Power is usually farther down on the list. In most cases, if your engine is equipped with a single exhaust system, a dual exhaust is the ideal first step to increasing power. For example, a ’72 307 single-exhaust two-barrel Chevelle will still respond favorably to a dual exhaust designed for a 350 SS Chevelle. And the upgrade is probably a bolt-on.
Walker builds dozens of factory-style replacement dual exhaust systems for all kinds of cars. Do a little research at the parts store to determine what’s available for your car. For many late-model cars, catalytic converters prevent you from legally modifying the exhaust ahead of the catalytic converter, unless the components are certified. However, you can legally alter the exhaust after the cat any way you wish. That makes the selection of so-called “cat-back” components important, especially the muffler. Walker, Borla, Flowmaster and others offer many high-performance mufflers that will do the job.
Induction-
Induction is where most enthusiasts start in a hi-po buildup, but a better intake and carburetor will perform only if the exhaust flows properly. Wise choices for induction changes include dual-plane intake manifolds and a conservative carburetor selection. Dual-plane intakes such as Edelbrock’s Performer, Holley’s Contender and Weiand’s Action-Plus will improve torque. That’s what you’ll feel in the seat of your pants. When replacing a two-barrel carburetor, don’t go overboard with carburetion. The Holley 0-1850 600-cfm carburetor will work well on any mild small-block.
But don’t overlook the stock Rochester Quadrajet, FoMoCo or the Mopar Carter-built four-barrels. They are all quality carbs when rebuilt properly and can offer great performance at a low cost. And don’t forget to include a K&N air filter with this swap. The K&N is better than any paper filter, and you can clean and reuse it when it gets dirty.
Fuel Delivery-
You can’t make power with a fuel-starved engine. In most cases, stock mechanical or factory electric fuel pumps are adequate for mild engines (making around 300 horsepower or less). Make sure the entire fuel-delivery system is adequate. We know of several occasions when a killer fuel-delivery system was thwarted by a kinked factory fuel line. Even small 5/16-inch fuel line is sufficient for 300 horsepower. Think about replacing that wimpy inline fuel filter with a high-flow filter.
Headers-
Adding headers at this point should really pump up the performance. While headers are certainly worth power, they will add even more performance when combined with the previously mentioned changes. You could also add headers at the same time as the dual exhaust. When choosing headers, stay conservative. Small-tube headers for a mild small-block will definitely improve low- and midrange torque (where your engine spends most of its time) while still increasing top-end power. For 350ci-or-smaller engines, 1-5/8-inch primary-tube headers are the largest you should use. If 1½-inch tube headers are available, use them, especially for 302- and 305ci engines. This is also a great time to consider adding a crossover or H-pipe to the exhaust system. That will add torque at no expense to top-end power!
Ignition-
Ignition systems are like exhaust systems. They usually don’t create power, but if the ignition is weak or defective, it can definitely cost power. First of all, there’s nothing wrong with a well-maintained, points-type ignition system. Points are only suspect because you must maintain the proper dwell angle, which changes as the rubbing block wears. Also, some cheap, generic points are junk at over 4000 rpm, so always buy quality, name-brand points. Don’t go for a killer coil with a points system because the increased amperage draw will burn the points up prematurely, especially if the engine is idled for long periods.
An important step is to always use a high-quality plug-wire set. We’ve seen an otherwise stout engine fall on its face from a brand-new set of $9.95 plug wires. If the wires are more than five years old, replace them with the spiral-wound wrapped wires from ACCEL, MSD, Jacobs, Moroso or others.
Traction-
Now that your engine is making more power, it’s probably spinning the tires. The best way to solve that is with bigger, wider or stickier tires. M&H and Mickey Thompson both offer soft-compound tires, but they are expensive and obviously don’t last very long. Other choices to improve traction using your existing tires include traction devices such as traction bars for leaf-spring cars. These aren’t crucial unless you have a wheelhop problem. For coil-spring cars, Air Lift makes air bags that allow you to preload the right rear side of the car to aid traction, especially if you have an open differential.
A positraction device is probably the best overall choice for any performance car, simply because it is transparent during the day-to-day operation of the car—yet it aids traction by driving both tires under acceleration. Deeper gear ratios (changing from 3.08 to 3.73:1, for example) will also help acceleration, but you pay the price of excessive rpm on the highway (see the sidebar “At Any Speed”).
Camshaft-
Notice that a bigger camshaft is far down on our list of modifications. That’s because the add-on pieces above are easier to install, and after making those changes, you probably have a solid running car. Again, the key here is to create a matched package of conservative pieces, such as a dual-plane intake, small carb, small headers and an excellent exhaust system. Match that with a conservative camshaft and the engine will respond. Stay with a short-duration, hydraulic, flat-tappet cam that has a little more lift and duration than your stock cam. Also, keep in mind that the cam swap will require new gaskets, and adding a new timing chain and gear is a good idea as well.
Heads-
Most hot rodders can’t afford a trick set of aluminum heads, which is too bad because this is an area where spending a little more money can really pay off. Of course, you still must remain conservative to prevent killing torque, but Edelbrock and Air Flow Research both make emissions-legal small-block Chevy heads that will add serious power. World Products also makes a replacement iron head that flows well. Of course, rebuilding your stock heads is an excellent way to increase power on a budget. But price all this work first. You may find that the machine work and parts add up to almost the same amount as a new set of aluminum heads!
Drivetrain-
Now that you’re making all this power, it’s time to take a closer look at the drivetrain. For automatic-equipped cars, a higher stall-speed torque converter is one way to drop your elapsed time, but you pay the price of “mushy” throttle response. For an everyday street machine, keep the stall speed at 2200 rpm or less.
For manual-transmission street machines, a good shifter is a must. There’s nothing more frustrating than a balky shifter that tends to lock up when you least expect it. An excellent street-clutch combo is the Centerforce matched with the new Dual Friction disc. This combines excellent holding power with soft pedal pressures that make it easy to live with on the street.
Put it all together and you have the makings of an excellent daily-driven street machine. This modular approach allows you to make changes as you can afford them while still enjoying your car along the way.
At any speed-
As you can see by this chart, tire diameter and gear ratio have a dramatic effect on cruise rpm. One way to lessen the high-rpm effect of a deep rear gear like a 4.56 is to use a taller tire for daily driving, then switch to a shorter tire for racing.
This chart assumes zero drivetrain slippage. When using a nonlockup torque converter, these rpm levels would be higher by approximately 200 to 300 rpm or more due to torque-converter slippage.
http://hotrod.com/tipstricks/p108534_image_small.jpg
[/hotrodarticle]
Keep in mind this is the pretty basic of basic modding here. It varies from import and domestic and also the kind of budget, IMO there's a few things that could have been mentioned but this article was mainly for beginners. If anyone wants to have a discussion on this and have INTELLIGENT modification discussions, i'm always open for one. :biggrin:
CivRacer95
09-19-2005, 01:34 PM
...:sleep:
:grinno:
Very imformative joshy. Good write up, or copy, however you got it here. It's good.
:grinno:
Very imformative joshy. Good write up, or copy, however you got it here. It's good.
-Josh-
09-19-2005, 01:37 PM
...:sleep:
:grinno:
Very imformative joshy. Good write up, or copy, however you got it here. It's good.
Yeah it's long, but i still enjoyed reading it
:grinno:
Very imformative joshy. Good write up, or copy, however you got it here. It's good.
Yeah it's long, but i still enjoyed reading it
street_racer_00
09-19-2005, 02:25 PM
If I had enough time to mess with all that stuff, I would have no job and wouldn't be going to school.
-The Stig-
09-19-2005, 05:53 PM
Stuck!
GreyGoose006
10-04-2006, 11:13 PM
in the tire dia. vs. rpm chart, is that assuming a 1:1 trans ratio?
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