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Abby’s Guide > Outdoor Power Equipment (Lawn Mowers, Snow Blowers, Chain Saws and more) > Discussions > That thing got a Hemi????

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Emmo


Joined: May 22, 2003
Points: 1065

That thing got a Hemi????
Original Message   Jul 16, 2005 1:14 pm
Replies: 7 - 16 of 23Next page of topicsPreviousNextNext page of topicsAllView as Outline
Roger


Joined: Mar 1, 2005
Points: 355

What is a hemi?
Reply #7   Jul 16, 2005 11:30 pm
For those of us who are ignorant, could someone please define what a hemi is and does.

Thanks

Majorxlr8n


Location: Freehold NJ
Joined: Aug 6, 2003
Points: 1092

Re: That thing got a Hemi????
Reply #8   Jul 17, 2005 1:22 am
The word HEMI is actually short for hemispherical. In a piston engine, the area from the top of the piston to the top of the cylinder head by the valve heads is known as the combustion chamber (this is actually just an area of air!). The combustion chamber on most overhead valved AUTOMOTIVE engines are either wedge shaped (think of a piece of pie) or hemispherical (think of tennis ball cut in half). The cylinder head design dictates the combustion area shape, so when someone says "hemi", it really only refers to the engine's cylinder head having a hemispherically shaped combustion chamber.

Hemi heads have the spark plug located at dead center of the combustion chamber, which makes for an extremely efficient & powerful fuel/air mixing & flame burn (actual igniting of the fuel/air). Hemi heads also have ideal valve placement to help the flow of air (intake & exhaust) through the cylinder head. In simple terms, the head design is VERY efficient, and allows an engine to make excellent power! On the downside, hemi heads themselves usually are quite heavy & large, and valvetrains can be somewhat complex (read: expensive).

Wedge shaped combustion chambers are what most OPE engines have, as do most automotive engines. The "wedge" shape by design, is not as efficient as a "hemi" due to all the sharp angles that are present, which creates turbulance. The valve placement & spark plug location are less than ideal also. Cost was a big factor that lead to the wedge design. However, a wedge chamber CAN be modified to produce very impressive burn & airflow rates - having said that, IMHO all this "HEMI" talk (car & truck commercials) as of late really doesn't impress me personally. Chrysler/Daimler is really getting a lot of hype & sales out of it though...

There is another variation of head called a semi-hemi, but it is not widely used. It is actually a cross between a wedge & hemi shaped combustion chambers.

Marty

This message was modified Jul 17, 2005 by Majorxlr8n


Bill_D


Nice day for a mow!!

Location: Chicago
Joined: Dec 6, 2002
Points: 920

Re: That thing got a Hemi????
Reply #9   Jul 17, 2005 6:41 am
Bruce Willis has a vintage bike w/ a semi, hemi, Demi, in it. (Rim Shot)
Garandman


Location: South Boston, MA
Joined: Mar 10, 2005
Points: 341

Re: That thing got a Hemi????
Reply #10   Jul 17, 2005 7:39 am
This one doesn't but it's got a 454....



Item #7701609184 on eBay.
Marshall


As Long As There Are Tests, There Will Be Prayer In Public Schools. ;- )

Joined: Sep 16, 2002
Points: 7730

Re: That thing got a Hemi????
Reply #11   Jul 17, 2005 10:55 am
Bill_D wrote:
Bruce Willis has a vintage bike w/ a semi, hemi, Demi, in it. (Rim Shot)

ROFL


Garandman, that thing is awsome. With open headers, I'm sure it gets the neighbors attention.
snowshoveler


tides in dirts out surfs up

Location: bridgewater nova scotia...aka the swamp
Joined: Jan 3, 2003
Points: 1261

Re: That thing got a Hemi????
Reply #12   Jul 18, 2005 11:08 am
well well well...

i looked at the hemi snowblower sunday and somthing just didnt look right.

so today i looked a bit closer...the augers are in backwards.

this just goes to prove it dosent matter how much money you have you can still be a dumbhead.

i bet i can get it to work a lot better than the idiots that put it together.

gee and i dont have the backing of chrysler either and i apparently am a bit smarter.

later chris

craftsman 10/28 snowblower with tracks   husky 372xpg chainsaw   sachs dolmar bc212 bushsaw   mondo trimmer   monster tractor with trailer    cheep wheelbarro and couple shovels and a partridge in a pear tree 
bontaiJoe


If it's free, it's for me!

Location: Saylorsburg, PA
Joined: Jun 4, 2004
Points: 424

Re: That thing got a Hemi????
Reply #13   Jul 18, 2005 12:16 pm
Those snowblowers would probably launch gravel THROUGH your house. Some of us know what happens when you hit a hidden wet newspaper with a conventional snowblower... (it jams the auger and stops a 5-9 HP engine. What is gonna happen if there is 300 HP behind that auger when the wet newspaper hits? Something is gonna break and break BIGTIME!

"Man's mind stretched to a new idea, never goes back to its original dimension." -Oliver Wendell Holmes
Marshall


As Long As There Are Tests, There Will Be Prayer In Public Schools. ;- )

Joined: Sep 16, 2002
Points: 7730

Re: That thing got a Hemi????
Reply #14   Jul 18, 2005 12:42 pm
snowshoveler wrote:
well well well...

i looked at the hemi snowblower sunday and somthing just didnt look right.

so today i looked a bit closer...the augers are in backwards.

this just goes to prove it dosent matter how much money you have you can still be a dumbhead.

i bet i can get it to work a lot better than the idiots that put it together.

gee and i dont have the backing of chrysler either and i apparently am a bit smarter.

later chris


It just looks backward in the photo. LOL
Roger


Joined: Mar 1, 2005
Points: 355

Re: That thing got a Hemi????
Reply #15   Jul 20, 2005 12:30 am
Majorxlr8n wrote:
The word HEMI is actually short for hemispherical. In a piston engine, the area from the top of the piston to the top of the cylinder head by the valve heads is known as the combustion chamber (this is actually just an area of air!). The combustion chamber on most overhead valved AUTOMOTIVE engines are either wedge shaped (think of a piece of pie) or hemispherical (think of tennis ball cut in half). The cylinder head design dictates the combustion area shape, so when someone says &quot;hemi&quot;, it really only refers to the engine's cylinder head having a hemispherically shaped combustion chamber. <p>Hemi heads have the spark plug located at dead center of the combustion chamber, which makes for an extremely efficient &amp; powerful fuel/air mixing &amp; flame burn (actual igniting of the fuel/air). Hemi heads also have ideal valve placement to help the flow of air (intake &amp; exhaust) through the cylinder head. In simple terms, the head design is VERY efficient, and allows an engine to make excellent power! On the downside, hemi heads themselves usually are quite heavy &amp; large, and valvetrains can be somewhat complex (read: expensive).</p><p>Wedge shaped combustion chambers are what most OPE engines have, as do most automotive engines. The &quot;wedge&quot; shape by design, is not as efficient as a &quot;hemi&quot; due to all the sharp angles that are present, which creates turbulance. The valve placement &amp; spark plug location are less than ideal also. Cost was a big factor that lead to the wedge design. However, a wedge chamber CAN be modified to produce very impressive burn &amp; airflow rates - having said that, IMHO all this &quot;HEMI&quot; talk (car &amp; truck commercials) as of late really doesn't impress me personally. Chrysler/Daimler is really getting a lot of hype &amp; sales out of it though...</p><p>There is another variation of head called a semi-hemi, but it is not widely used. It is actually a cross between a wedge &amp; hemi shaped combustion chambers.</p><p>Marty <img alt="" src="/components/FCKeditor/editor/images/smiley/msn/shades_smile.gif"/>

Great response! Thanks!!!
newjerseybt


You want it done right?...You better learn how to do it yourself!

Ariens 1128DLE
Ariens 8526LE
Honda HRC216
Bosch 3221L
Craftsman DYT4000
Stihl FS90R


Location: Honesdale, PA
Joined: Dec 19, 2004
Points: 171

Re: That thing got a Hemi????
Reply #16   Jul 20, 2005 7:07 pm
I got the Hemi thing in my 2004 Dodge Ram. It's....just OK. If the truck were 2000 pounds lighter and had a 410 posi rear instead of the 276 or what ever it has now...it would haul a$$. I wish it had dual stainless steel exhaust. It probably would have an additional 15 HP. 
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