Brainful

am not sure if the question am going to ask is being answered before or not , but i really searched for it .. i know that the LQ9 heads are 71 cc along with the stock flat pistons , and i also know that the LS1 heads are 67 cc with the same stock flat pistons .. ls1 stock bore is 3.9 Vs 4.0 for the LQ9, and i also know that both champer compression is 10.1 ????? what i dont know is why a different chamber size has the same compression when the pistons are both flat ?

is there is something i dont know ?

P.S:am not a newbie

Rick@Synergy

iTrader: (5)

Because size of bore does place a role in compression. if all being equal on two motors, you increase bore on one motor, you get more compression. Simple.

Rick

Brainful

i thought the head bore is 4.0 in the Lq9 heads ? thats what i noticed

Grimes

iTrader: (3)

compression ratio will change whenever you change any of the volumes in an engine - swept volume (bore and stroke), chamber volume of the heads, even changing gaskets (thicker or thinner) will affect the compression ratio.

A certain head and combustion chamber does not have a compression ratio associated with it. Only on a specific engine will they have a specific compression ratio.

Brainful

thank u grimes , i really know that the head gasket has a big rule in compression when i ordered a .55 gaskets and after installing everything i realized that i milled the heads .2 and got a thicker gasket shiiit , what am trying to learn is .. what is the relation mathmatically between bore Vs stroke Vs chamber size Vs compression
i.e what if i use heads that is 4.0 in bore along with a 3.9 bore and a 3.62 stroke , chamber Volume is 62 cc , head gasket is .45 . flat pistons WHAT will be the compression .. what is the relation ! thats what am asking about

Grimes

iTrader: (3)

No problem at all.


Well, basically compression ratio is:

(entire volume of space including chambers with piston at bottom dead center) / (entire volume of space including chambers with piston at top dead center) =
compression ratio

That is a very generalized equation, but it will give you a good idea to start with.

Hereis a pretty decent car craft article that will answer your question in detail:

http://www.carcraft.com/techarticles/982/

Brainful

thank u again and again , it is a great article .. very helpful this is exactly what am talking about , guys u have to read this if want to learn about compression in order to manipolate it the right way ,,

a question came to my mind .. what is the LS1 stock Clearance volume ? stock piston deck height ?