ibanez7

iTrader: (7)

I wrote this in an email for a friend, explaing what heads and cams do.
He is new to the performance side of things.. He is not mechanically inclined. So I had to write as simple as possible..


So what do you guys think of this write up

here is the cam and heads write up.

Cam and Heads:

Think of your engine as a giant combustion air pump. You need 3 things in order to run, GAS, SPARK and AIR (they need to happen in perfect timing).

Cam and Heads control the air flow, both on the intake and exhaust.

A cam is the master of air, telling the slaves, the components inside the heads what to do and when.

The cam tells the heads when air can come in (intake) and when air has to leave (exhaust), while also controlling the amount of air, on intake and exhaust.

This control is for the air, that enters and exits the combustion chambers above the pistons, where spark and gas mix with the air causing the pistons to go up and down. Making horsepower.

The more air you get into the engine and out of the engine and the speed it does this, creates more HP.


so lets break down the properties of a cam, before we discuss the components in heads. I will use my aftermarket cam in my camaro for example

My cam has a grind (the grind being the size and range the cam was cut) of -
231/237 .590lift/.595 lift with 112 LSA

What the hell do those numbers mean??

They mean this:

231 = DURATION the amount of time measured in degrees (such 90 degrees or 360), that the cam allows intake air to enter the engine

237 = DURATION the amount of time measured in degrees, that the cam allows exhaust air to leave the engine.

The cam does this by holding the Valves open in the heads. Will explain valves when we get to the heads.

.590 = LIFT the distance the valves in the heads open on the intake air

.595 = LIFT the distance the valves in the heads open on the exhaust air

Cams are rotary in motion since they spin, the lift is a linear motion.

Think of both duration and lift as, if you turn the handle on your front door 90 degrees, you can open your door 3 inches and allow air to flow, but if your turn the door handle 260 degrees now you can open your front door 10 inches and flow more air. Pending which way you open the door, air either comes in or exhausts.

The last number

112 LSA = lobe separation angle is the control of air being (the lift and duration) overlapping each other. I could write a book explaining this part so I will keep it simple.

The higher the number lets say 118 or 120 will make a car have a smooth idle, the 112 that my cam has, makes for a very rough, bumpy mean sounding idle and engine.

Now the LSA does more then just sound. Sound is the by product of the LSA and your piston leaving Top Dead Center and the exhaust valves being open partially during the opening of the intake valves.

These 3 numbers LIFT, DURATION AND LSA, make up the cams profile/shape

Damn that is the easiest way to write it. Its alot of science of mechanical motion and timing to control air flow THROUGH THE HEADS...

perfect segway- HEADS and their components (slaves to the cam):

Heads are made up of various components called Valve train, those components are (only covering some of them):

(the order i listed these is the order they are in relation to the cam)

-lifters = follow the cam profile (the cams elliptical shape) in a rotary kind of motion. They ride along the cam profile and push the next item-

-pushrods = are connected to the lifters and pushed in a linear motion by the lifters, pushrods push against the next item

-rocker arms = are exactly that, they are like a rocking chair and rock back n fourth based off when the pushrods push against them.

-springs = are connected to the rocker arms, and make sure all of the above components have constant pressure against the cam, to follow its profile.

-valves = are connected to the rocker arms, by going through the center of the springs, as the rocker arm moves the valve opens or closes. (its your front door)

When the valve opens, its allowing air to enter the combustion chamber of the engine or exit the engine.

All of the above components are in the heads, minus the lifters which sit inside the engine block below the heads and follow the cam, which in our engine is in dead center of the block.

The pushrods are partially in the engine and in the heads.

Back to the Heads themselves, the heads sit above your pistons. Your intake manifold and exhaust manifold (headers) are connected to the heads. The heads are just a bunch of chambers for air to enter or exit in relation to the piston. Air flows like this - into your intake, into the heads, into the combustion chamber, back into the heads, and out through your exhaust. The cam controls when and how much of the air.

how heads and cam help a car and give the engine killer horse power and face pealing sound.

Heads - if the chambers are bigger (to the right size) angled correctly and polished (meaning smoothed and rounded edges), more air can flow in and out of the combustion chambers.

Allowing more explosive combustion in the engine, resulting in more hp.

So if a cam controls the amount of air and when the air enters or exits, altering this control or modifying it, you can greatly increase the amount of air, giving your engine the ability to unleash the fury of HP, and sound mean when doing it.

here is a link with good diagrams to compliment what I wrote. really watch the diagrams.

http://auto.howstuffworks.com/camshaft.htm

[I]final note, whenever you add heads or cam, or both, you will need to have your engines computer tuned. This tuning allows for the air, gas and spark to be properly set up. If not you, can pop your engine.[/I

firstls1vette

hey wow thanks man saved me a lot of research in a couple months when i decide to finally do a cam swap. i knew how they worked and what they did just didnt know what all the numbers ment. knowing that should make it easier to pick one out. say by the way do you know what size a stock ls1 has in it on an 03

SOMbitch

iTrader: (8)

^^^^Pretty sure at .050 it is 197/207 .467/.479 116LSA

colinpd137

iTrader: (17)

Nice write-up, saves me time on searching. bookmarked for later thanks

bones_c

iTrader: (3)

newbie here... whats the .050???
and i know from reading prior posts that cams and heads are preference but... what is considered "good" and "worthy" at the track?
i also understand that there is a relevance with cams and heads... what size heads should you go with for what size cam?

also is that the same stock specs for a 99 trans am?