jem7vwh

I have to admit, I don't know much about engines whatsoever. I want to know- but I don't have anyone to teach me. I thought initially that just by hanging out here, I'd pick up some of it. And I do know more than I used to.

I now understand what turbochargers and superchargers do. I completely get that more horsepower is always a good thing. But I don't really understand any of the jargon, for instance..

* what's a Cam? And what makes a good or bad one?
* what do the gears do? And which ratio are best?
* what do the heads do?
* what do the O-rings do?
* Why is everyone always modding their intake? Eidelbrock's etc?


Also, it is my *understanding* that compression refers to the amount of air that is forced into the piston each time it fires. Thus, the higher the compression, the better the explosion and the more power transferred to the drivetrain. Is that correct?

Any help you guys can offer would be awesome :)

45ACP

http://www.howstuffworks.com/category.htm?cat=Eng

Pete79L82

I will try to keep it as basic as possible.

* what's a Cam? And what makes a good or bad one?
A cam(camshaft) is what controls the opening and closing of the valves. There is not a "good one" or "bad one"(unless it is deffective). By choosing a cam that is a correct match for your other engine components it will make the engine more efficent in the RPM you choose, Thus creating more power in that RPM range.

* what do the gears do? And which ratio are best?
I think you are reffering to the ring and pinion in the rear differential. A lower gear(higher numerically), 3.70, 4.10, ect will multiply the torque of the engine and will give you more low end power but a higher RPM operating range. A higher gear(lower numerically), 3.08, 3.55, ect will lower the RPM operating range and will give you less low end power but better fuel economy. Again it is choosing the correct one for your application.


* what do the heads do?
Cylinder heads direct the air into and out of the engine. More efficient design heads allow more air to get into the engine and gets air out of the engine with less restrictions there by creating more power. (Combustion chamber design plays a part also but that gets a little more detailed.)


* what do the O-rings do?
If you are reffering to them on an engine then you probably mean valve stem seals. They are meant to keep oil from getting into the engine through the valve guides. (There are also o-rings on Corvette brake calipers which is an improved design over the original square seal type)


* Why is everyone always modding their intake? Eidelbrock's etc?
Intake manifolds are like heads, they allow more air to enter the engine more efficiently. The better designs flow more air while keeping the fuel/air mixture suspended for more power.

Heads, intake manifolds, and cams must be matched together to get the best power in the desired RPM band.


Also, it is my *understanding* that compression refers to the amount of air that is forced into the piston each time it fires. Thus, the higher the compression, the better the explosion and the more power transferred to the drivetrain. Is that correct?

Compression ratio refers to the the difference between the amount of space in the cylinder when the piston is all the way down (BDC or Botton Dead Center) versus the amount of space when the piston is all the way up (TDC or Top Dead Center) and example whould be if the cylinder hold 500cc'c at BDC and then holds 50cc's at TDC then it would be 500/50=10 to 1 compression. The higher the compression the more pressure is developed in the cylinder creating more horsepower but higher compression requires better fuel and puts more stress on the engine components.

I hope this answers some of your questions.


[Modified by Pete79L82, 8:17 PM 8/28/2002]

VegasJen

whew! where to start?
o.k. cam: a cam is an eccentric lobe (think pear shape) that is used to activate something. in this case a valve. a camshaft is a shaft with a series of cam lobes that runs the length of the engine containing 17 lobes. 16 operate the valves via a rod and fulcrum system (lifter, pushrod, and rocker arm). the other one operates the fuel pump. the camshaft is driven by a gear and chain from the front of the crank. as the camshaft turns, the smaller portion of the cam lobe allows the valve to stay closed, when it comes up on the peak of the pear shape, it opens the valve. make sense. a "good" cam is one that is matched to the engine, "all good things in moderation". you don't want a small engine a cam that opens the valves too early, opens them too high, holds them open too long and closes them too late. that would be a bad cam. small engines like small cams, big engines like big cams. certain cams can be matched to give different results like more power real low like pulling away from a stop light and some cams give you lots of power way up high. just depends on what you want.
gears: geez, there's alot of different type of gears. like i said above, the cam is driven off a gear from the crank. think bicycle: the crankshaft has a gear on it like the pedal portion of your bike. the cam has another gear on it like the back wheel of the bike. the chain connects them because they both spin the same direction, just like the bike. in our cars, the cam turns half as fast as the crankshaft, therefore the cam gear is twice as large as the crank gear.
there is a different set of gears in the rear end of the car. their purpose is to take the drive shaft, which runs long-ways through the car, and turn that energy to the side to drive the wheels. sorry can't think of an example of that one. just like cams, the best ratio depends on what you want to do. gears are measured by the amount of reduction they provide. like a pulley system, they give you (your car) leverage. the higher the number, say 4.11:1 the more leverage you have. this is great for acceleration but limits how fast it can ultimately turn. just like the gears of a 10 speed. 4.11:1 stands for how many revolutions the drive shaft turns for each revolution of the wheel, i.e. 4.11 driveshaft revolutions for each revolution of the wheel. the lower (numerically) the number, say, 2.72:1, the less leverage the engine has. this is terrible for acceleration but great for highway cruising.
heads: heads contain the valves and the passages that the air flows through going into the combustion chamber and out of it. the valves open and close by the cam as described above.
compression is not the amount of air you get in the engine it is the amount of 'squeeze' you put on the air in the engine. the best way i can think to describe it is like this: say you get a container and it's full of air. now this container has a lid that can slide up and down inside the container without letting the air out. with the lid all the way down, the container is 100% full and no compression. it's atmospheric pressure. now when you push the lid down into the container without letting air out, you increase the pressure. if our container is ten inches long and we push the lid down nine inches, we have a compression ratio of about 9 to 1 because we have just compressed 10" worth of air into a 1" space. this is important because that contains energy. when we ignite our spark plug in our container (engine), it burns the fuel, increasing the pressure and pushing our lid (piston) back down. that turns the crankshaft the same way your legs turn the gear on your bicycle when you push down on it. you don't want and explosion in the engine because explosions are uncontrolled. you want a controlled burn. make sense?
o-rings: i'm assuming your referring to the o-ring seals in the brakes. they just seal the piston in the piston bore and keep your brake fluid from sqirting out all over the place. o-rings seal things, they are not used extensively inside the engine, thus my assumption.
everybody 'mods' their intakes, and exhausts, and heads because, generally speaking: more air in=more power out. as said before, the key is everything needs to match. you can't put a carburetor from a 454 cubic inch chevy on a honda civic and make more power.
any more question? :) :cheers:

DollaGreen

I read a book, John Lingentelter on modifying small block chevy engines. He goes into detail about what each part does and what makes a certain type of each part better. IE heads, cam, exhaust etc. It is easy to follow. I read it in about 3 hours and that was going back and rereading to understand a lot of times. It is a good place to start! BTW dont be discouraged, it will all of a sudden all come together for you. :cheers:

glenga

I assume you already have a Vette or thinking of getting one. Best way to learn is through this site, books and practice. Before I got my C3 I also knew very little about mechanics and now I am confident enough to tackle most jobs on my own. C3s are generally easy to work on :bs well, mostly.

Anyway, have fun.

Paul 75 L82

Start buying Chevy High Performance magazine.

jem7vwh

I don't currently own a Vette. I'm a poor college student. This fall I will likely purchase a Toyota or Honda :cry that I can drive with little to no worries until I finish school in '04. But my plan is to get a '73 vette ASAP. Understanding that even the best condition cars need work when they're 30 years old- I decided I needed to learn as much about working on Vettes as possible before I even bought one.

Fevre

Good year chose and wise move to learn as much as possible before buying. I knew some about cars but wish I had known more before buying my first vette. Keep lurking and keep learning adn soon enough you will be part of the brotherhood. How do I make 'brotherhood' non-gender specific? You'll be part of the 'hood'?:)


[Modified by Fevre, 8:48 AM 8/29/2002]

ZD75blue

Heres a tip for you... 1982-1994 Camaro, V8 an in the 1k range

your generic 25 dollar starter fits it...

Extremely easy on the wallet :cheers:

ericshaw

Break one when your wallet's empty and summer has just begun... that's how I learned real quick. :D