HEADS
Usually the more air the merrier, but there are other considerations to this such as what RPM range are you planning on running and the ideal street ability of your engine. A 4v application is a handy choice but what it really comes down to is high intake velocity and cfm characteristics of the head for the application you tend on using it for.

Port Matching - when parts are cast and bolted together they usually never line up right. This is where a port match comes in handy. The more even the ports the better the flow rate and less restriction in the intake / exhaust area.

Polishing - polishing creates a smooth even surface for air to flow over. The smoother the better and the faster exhaust and intake air can flow. Intakes should only be smoothed to about a 120 grit finish to allow some turbulence. This turbulence is great for air fuel mixing.

Valve Seat Blending - blending the valve seats into the combustion chamber area creates a smooth area for air to enter the combustion chamber rather than a stepped area which would cause turbulence and restrict airflow.

Un shrouding the valves - Un shrouding the valves opens up the area around the valve so that air can flow freely into the combustion chamber.

Un shrouding the plug - Un shrouding the plug allows for the air fuel mix to better reach the spark kernal. This helps ignition of the air fuel mix which creates more power.

Spark plug location - Setting up the spark plug so that the electrode faces away from the intake valve is a smart idea. This is done in high end racers so that the spark kernel is exposed directly to the air fuel mixture.

Material Type - Iron heads are great in that they retain heat. This retention of heat creates more power but is detrimental to spark timing. Advancing spark timing is essential in creating power but to much will cause detonation and destroy your engine. An aluminum head will draw heat out of the combustion area allowing for a better spark advance than the iron head.

INTAKE CHOICE
Intakes are a large part of power creation. Again, you will have to look at where your engine power band will reside and makes changes accordingly. A long runner intake will create a lot of torque and power down low where a short runner design will create more top end power. Ford makes a variable geometry intake that changes runner length depending on rpm. This is used on their race engines and is an awesome piece. Most other people have to take their pick from runner length. I opted out of using the variable geometry intake and chose an intake that would offer power increase from 3000-7500 rpm and sacrifice about 7lbs of torque down low which in my opinion is a fair tradeoff for 30+hp.

CAM CHOICE
Again you want to match the characteristics of the head to the cam rpm range. VTEC is great in that the intake duration and lift changes based on rpm. This allows for the best of both worlds. Great bottom end torque and power and great top end power. Cams should also be matched to the engines rpm powerband as well as other factors such as supercharging or turbo charging. Usually a turbo cam has a longer exhaust duration or lift to increase the exhaust energy to the turbo where a supercharged or naturally aspirated engine likes a longer intake duration and lift.

With all this new technology I wouldn't doubt seeing a VTEC type system with variable runner intake on engines soon. There are also prototype engines that alter engine compression ratio as well so that compression ratio is high in none boosted situations and lowers compression based on boost..... (new SR20 prototype). One thing I have learned with engines, you can never win. There will always be bigger and better down the road.

Cam Duration - the length of time the cam keeps the intake and exhaust valve open.

Cam Lift - the height it pushes the intake and exhaust valves into the chamber.

VALVETRAIN
It is important to do your research when doing a valve train upgrade and DO NOT RECCOMEND upgrading one piece of the valve train only. Many people encounter problems in the valve train when doing that such as broken springs etc due to harmonics. By changing one piece you alter harmonics in the valve train and harmonics at the right frequency can damage ANY material so it's best to use one manufacturer and buy locks, retainers, springs and valves as a package.

Dished Valves - A high RPM street valve is usually dished. Since a robust valve is usually heavier they lower the weight of the valve by dishing the bottom of it. This increases engine rpm ability. Heavier valves can float. This floating will cause massive engine power loss and potentially damage the engine. I can get into valve float but lets just say that it happens due to aggressive cams, low spring pressure and valve weight. An aggressive cam moving a heavy valve can actually throw the valve open longer than it should be due to little spring pressure. The only negative to dished valves is that they lower the compression ratio of the engine.

Material Type - There are many types of valves including titanium, stainless steel and inconel (same as turbo turbines). The inconel valve can handle extreme heat and abuse. The titanium valve has extremely light weight and allows for higher revving capability with more aggressive camshafts, but are not a good choice for road applications due to material elasticity. Titanium valves must be replaced every so often. A worthy road valve is stainless steel. It can be used all day every day and be fine. To reduce weight of the valve dishing and gun drilling the stem is done for high rpm capability.

Multi Angle Valve Job - gah... I'm getting tired writing here.... lets see. The valve sits in your heads and is sealed. Basically where the valve sits is a flat shot so the air entering the combustion chamber has to make sharp moves, this is a no no for airflow and velocity. So what people commonly do is give the valves a multi angle valve job. This smoothes out the corners so that the air fuel mix flows easier into the combustion chamber area.

HEADER CHOICE
Again engine rpm capability should be looked at when choosing a header.

Longtubes - offer high end rpm power but usually sacrifice bottom end power.

Mid length - rare to find but offer a combination of top end power and bottom end torque. (My choice)

Shorty - offer good bottom end power, better than stock top end power but not as much top end as long tubes or mid length headers.

I got a little lazy with the explanation of stuff the closer I got to the end. Either way this is a lot of info and hope I've helped you understand how to pull some more power out of your engine and how engines work rather than bolting up a bigger turbo. There is ALOT more to know but this is a great starting point. Until next time.

- \\'eapon X