Increasing compression is the most productive way to make power. Build compression into your engine and you build in power. In more than a century of internal combustion, there has never been a more common sense way to make power. Raise compression, but be careful about how you raise compression. Compression and cam selection go hand in hand because cam selection also affects cylinder pressure or working compression.
|Your engine builder can best advise you on compression and cam selection. Both have to be chosen in a spirit of cooperation where you get power without doing engine damage. Compression beyond 10.0:1 these days can cause detonation, spark knock, pre-ignition, or what is also known as “pinging” if you don’t have enough octane. Watch fuel and spark curves while you are bumping compression. And remember, pump gas isn’t what it used be. However, high octane, smog legal unleaded fuel is available if you have the budget for it in five-gallon cans.|
|5. Found-Bonus Power|
Think about this for a minute: Your engine actually produces more power than it delivers. Consider the power lost to internal friction, components that consume untold amounts of power just to move them. And consider how much heat energy is lost to the atmosphere that does nothing for power. Did you know your engine wastes 70-75 percent of the heat energy generated from fuel/air light off? Fifty percent out the tailpipe and 25 percent via the cooling system. This means we harness barely 25 percent of the fuel’s BTUs (British Thermal Units). Talk about waste. It’s insulting to efficiency experts everywhere.
|So how to reduce friction and free up power?|
Keep in mind that it’s always a tradeoff. When you go with low-friction components like roller tappets and rocker arms, you gain, but you also spend. Low tension piston rings and more liberal clearances mean some sacrifice of durability.
- Roller Tappet Camshaft
- Roller Rocker Arms
- Dual-Roller Timing Set
- Needle Bearing Cam Sprocket
- Low Tension Piston Rings
- Greater Piston to Cylinder Wall Clearances (within limits)
- Greater Bearing Clearances (within limits)
- Greater Valve to Guide Clearances (within limits)
- Windage Tray (oil windage at high rpm robs power)
How much of your vehicle’s driveline robs you of power? And though it may sound like an old saw, tire inflation and tire/wheel sizing are also factors in sluggishness. The greater your vehicle’s contact patch, the more power it takes to move you. Underinflated tires will make your vehicle feel like it’s chained to a tree under hard acceleration. Take tire inflation right to the tire’s limits depending upon ambient temperature. Temperature directly affects pressure.
|6. Velocity Stack|
A velocity stack is a trumpet-shaped device which is fitted to the air entry of an engine’s intake system, carburetor or fuel injection and improves airflow. The product reduces induction turbulence, which is why you can expect an increase in power.
|7. Fuel Line Right-Sizing|
You might laugh at this one, but you’d be surprised how often we get this one wrong. You’re not going to get 450 horsepower from a 5/16-inch fuel line. Think of it like trying to rapidly draw iced tea through a cocktail straw. You’re going to come up short. High-performance engines need fuel and plenty of it. Minimum fuel line size should be 3/8-inch for most applications. When horsepower rises above 500, you need 7/16-inch fuel line.
|8. Right Manifold for the Job|
Here’s another one that performance enthusiasts get wrong more times than not. While we’re so busy paying attention to horsepower, we forget to acknowledge torque. Torque is your buddy on the street, not horsepower. You want torque to hand off smoothly to horsepower at wide-open throttle. However, you won’t get there smoothly with a single-plane intake manifold.
|A dual-plane intake manifold offers great low to mid-range torque while also allowing an engine to breathe at high rpm. What this means in terms of power is greater torque numbers during acceleration and higher horsepower figures on top. It’s the dual-plane manifold’s long intake runners that give you torque, and high ceilings that deliver horsepower. One more thing: Consider the use of a carburetor spacer to get even more torque out of a traffic light.|
|9. Jet Set|
We’ve learned time and time again in dyno testing that jet swaps can go either way when it comes to power. Too much or too little can mean power losses, which is why it’s suggested you pick up a Holley jet kit and do a little experimenting. Go up one jet size at a time and see what you get beginning first with primaries, then secondaries. Always better to err on the side of richer than leaner. If you lose power as you go richer, start going backwards on jet size one jet size at a time. Go with a spark plug reading while you’re at it right after a wide-open throttle shutdown to determine course of action.
|If you’re running a carburetor with a fuel line screen at the fuel bowl, remove it while you’re in there. An in-line fuel filter is plenty enough and won’t hinder fuel supply.|
|10. Heads Up|
There was a time when cylinder head selection was decidedly modest for those searching for big street power increases. Today, selection is downright sinful. A good cylinder head swap will get you more power if you go about it correctly. Bigger doesn’t always mean better. Look at valve and port size along with flow numbers in order to make an educated decision.
|Remember, you want torque on the street, which calls for good intake velocity coupled with compatible exhaust scavenging. You don’t need huge valves and monster ports to get there. To get there effectively, you also want a camshaft profile that works well with the cylinder heads you are considering meaning good overlap and nice flow-through momentum.|