ok i have been hearing something on this site that i dont know quite what it means and i was wondering what some of this stuff means i have done surches but sometimes its doesnt clearly state the answer or i dont have the right spelling ok anyways

What are some terms that are important to know when getting a engine machined? (Ignorant people are usally taken advantage of)

When a head has 76cc what does that mean?

What does it mean when your fuel is Lean?

What does it mean when your fuel is rich?

What is octane? and what does it do?

I will think of more when they come to me

 

ill try to answer as many of your questions as i can:

1. cylinder head combustion chamber size, basically the "bowl" that the valves are in, that causes the combustion chamber (sealed area that piston is in when the head is on the block) to be a certain size. a 64cc head will give ya more compression than a 72cc head. smaller area, more pressure, understand?

2. too much air, not enough fuel

3. vice versa

4. kinda know what this means, not sure enough to try and make an educated guess, so i guess we'll both learn from this 'un, huh?


hope this helps!
Josh

 

octane...the basics, 87 octane burns faster than 89, 93, 110 ect, the higher the octane the slower and cleaner it burns. thats why if your car detonates or "pings" you put in a higher octane, the flame is exploding rather than burning and pushing down the piston.

 

For a good guide to general systems information, this link is decent:

http://www.acdelco.com/html/as_guide_main.htm

For a little more technical information on engines and building, this site is pretty good:

http://www.grapeaperacing.com/GrapeA...tech/index.cfm

 

in what situation would you need higher octane?

 

higher compression engines require higher octane

slight example:
let's say that you have 10:1 compression (the air and fuel gets compressed in the cylinder to a 10th the original size.. i believe)

this is high compression, and for the example, let's say you put 87 octane in the car, the car will probably studder HORRIBLY
this is because the gas is igniting and going off before the piston is at the top of the compression stroke, thus, the pistons are being forced in the opposite direction too quickly, and the car doesn't like that

so, you'd have to use a higher octane (prevents the fuel from igniting prematurely) and your car will run smoother

vise-versa is the same. high octane in a low-compression car will screw up the car, too. The gas WON'T detonate when it's required, or something

Diesel is essentially very high octane, I believe. Diesel engines don't have spark plugs, they compress the gas so much that the gas ignites, creating the detonation, or explosion, whatever you wanna call it. Diesel engines have in upwards of 20:1 compression, i think.

 

are there any formulas to figure out how much octane you need??

 

sure, you can do it in a Formula. An IROC-Z or a Z28 and even the Trans Am seem to work well too. lol, j/k. no, there isn't really a formula that i have heard of, the "pros" who have built a couple engines just seem to know what to use. you just start with say, 87, and if she pings, move up...

Josh

 

yep, ping means higher...

 

Octane is (in a way) a measure of how resilient a fuel is to combustion. The lower the octane (ex. 87) the easier it is for the engine to ignite, but also, the easier it is for it to burn itself (detonation, pinging). The higher the octane (ex. 104) the more resistant it is to combustion, making it harder for the engine to ignite properly. This is why it isn't a good idea to use the highest octane pump gas you can get in a low compression engine. The up side to this is that it is more resilient to self-destruction (detonation) in a very high compression engine.

Basically, to have the engine run its best and make the most power, you want to use the lowest octane fuel your engine can handle without pinging.

As far as pump gas goes, I wouldn't reccomend any higher than 10:1 with cast iron heads unless you and engine tuning whiz.

 

ok i know enough information about octane someone help me with this


For example when i want to get my car checked for cracks and see if its still good do i just say that or is there a word for it?

 

You mean the engine? You have the heads magnafluxed (special machne for checking for cracks) and get the block checked...they might use dye penetrant or eddy current to check it.

 

At the machine shop, you probably want to have the block bored and honed, the mains line-honed and the block (and maybe other parts too) magnafluxed, which is a method for checking for cracks.

 

whats it called when they straighten up the part of the block so that the gaskets fit better

I remember hearing this along time ago

 

You mean the head gaskets?

Thats called "decking the block".

 

yea thansk