that thing gotta hemi?

[Dan89rs]

this is really just to see if what i have been told is right. but i wanted to hear from the hemi guys themselves. my question is that hemi is short for hemispherical, correct? and that the combustion chamber is hemispherical? if so, is this do to the shape of the heads or pistons or both? and does the position of the spark plugs have to do with the extra power?

i just wanted to know so i dont sound dumb when talking cars. and if you guys know of any informative sites on the hemi id love to check them out. thanks.

[Dan89rs]

any one know?

[scoutinkeith]

yes, "hemi" is short for hemispherical. basically what it amounts to is a dome shaped head, the piston is still relativaly flat.
I'm not real clear on what exactly gives it the extra power, but I do know that the hemis (the new ones at least) have two spark plugs for each cylinder, but I think that is more of an emissions thing rather than for power.

[fredjacksonsan]

Two spark plugs are also for power; they're used in Corvettes, and also in piston airplanes since the 50's. Two sparks make faster and more even burning.

In a HEMI powered drag car, the pistons are also dome shaped to match the combustion chamber, which make for a much higher compression ratio. I'm not sure of piston shape in the 5.7.

[2000mudder]

the hemispherical shape of the head creates the best flow for the air fuel mixture to circulate thru the valves and the two plugs are to make sure all the fuel is burned as it goes flying out the exhaust valve.

[indyram]

Pretty much what it boils down to is more complete combustion, more efficient. This should help or try doing a google search. There should be plenty of sites out there.

http://www.automotiveforums.com/vbul...highlight=hemi