So uh....what is a Hemi?

Discussion in 'After Hours Lounge (Off Topic)' started by Travis Hedger, Jan 8, 2004.

  1. Travis Hedger

    Travis Hedger Supporting Actor

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    All over town I see billboards showing a Dodge truck with a bumper sticker that says "Yeah, it's got a Hemi" And commercials are starting to drive me nuts. Nowhere in these ads or signs does it say what the hell a hemi is. Based on the TV Ad it seems to have something to do with the power of the engine, but other than that, I am completely lost as to what a Hemi is, and why are they pushing it so hard in advertising?
     
  2. Patrick Sun

    Patrick Sun Studio Mogul

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  3. TedE

    TedE Stunt Coordinator

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    Hemi was a name Dodge used back in the 60's for muscle cars that had hemi-spherical heads in the combustion chamber (or some such). It actually gave a pretty significant power boost.

    On the same topic, does anybody know if the new Hemis *really* are Hemis? I heard rumors that they brought back the trade name and slapped it on engines that weren't really Hemis.

    Edit: based on the above links, I guess they really are Hemis
     
  4. DavidNighorn

    DavidNighorn Stunt Coordinator

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    Hemi is hemispherical chamber in the cylinder head of the engine. Normally the chamber is kind of wedge shaped. The purpose of the hemi is to increase the chamber volume, improve the flow of fuel and exhaust through the valves, and to increase power.

    Dodge made hemi engines back in the sixties and they are still custom made for drag racers. I think that the GTX was one of the main models that sported the 426 cubic inch hemi.

    Hope this helps.

    David
     
  5. Malcolm R

    Malcolm R Executive Producer

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    It's mostly just a trendy marketing phrase to make Dodge owners think they're getting something cool. Unfortunately, they're still driving a Dodge. [​IMG]
     
  6. Kirk Gunn

    Kirk Gunn Screenwriter

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    There was a previous thread on this, and I thought it mentioned that most current engines have hemi-spherical heads.

    Or perhaps that was one of my flashbacks ?
     
  7. Philip_G

    Philip_G Producer

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    Anyone know how they fit 4 valves in a hemi head? from what I remember of (reading..) about the shape, that would be difficult.

    edit: maybe I've answered my own question


    so if I read this right, the new hemis are two valve.
     
  8. Craig

    Craig Second Unit

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    Chrysler built engines with hemispherical combustion chambers back in the 50's. However the Hemi name really gained fame with the 426 Hemi that Chrysler built for Nascar racing in the '60s. They built a slightly modified version for street cars up until 1971. They were pretty rare and pretty expensive, you didn't see them much compared to other Chrysler engines like the 440 or the 383. The fact is however that they really were pretty much racing engines that you could get in a street car. You had two 4 barrel carbs on top. As the saying goes, it could pass anything on the road except a gas station.

    The Beast - 426 Cubic Inches
     
  9. Todd Hochard

    Todd Hochard Cinematographer

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    The "Hemi" head is characterized by a -surprise- hemispherical shaped combustion chamber in the cylinder head, and intake and exhaust valves that are on opposing sides of the head, inline with the direction of flow of gases through the cylinder and head.

    Virtually every single multi valve cylinder head (and a few two valve heads) out there today, from Honda Civics, to Mustang GTs, to Ferrari's 5 valve head, to motorcycles, use this technology/shape. As noted, Chrysler made it famous back in the early 60s, but had them in the 50s.

    Pics of an earlier Hemi head (1954 according to link) - http://www.thelittlelizard.com/Tech/tech2.htm
    Note the similarity to a Honda four-valve head- http://www.ericksracing.com/portingservices.htm

    This is contrasted by the "wedge" type cylinder head (e.g. small block Chevy to current LS1/LS6 Corvette motors, Mustang 5.0 motors), in which the combustion chamber is shaped -surprise- like a wedge, with one end being flat and the other more open. Valves alignment is usually perpendicular to the direction of flow.

    Terrible picture of wedge head- http://home.cfl.rr.com/todd80z28/car_image/Heads.jpg
    Flow is in the bottom, out the top, in the picture.

    Hemi heads typically have higher flow potential than wedge heads, but Chevy gave pause to that idea, with the unbelievable flows on the LS1/LS6 heads. However, even they've relented- the new three-valve head for the upcoming LS2 motors will have a hemi shape.

    Todd
     
  10. Lee L

    Lee L Supporting Actor

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    Call me crazy, but I'll go out on a limb and say I think the name means they use a cylinder head with hemispherically shaped combustion chambers.
     
  11. Vincent_S

    Vincent_S Second Unit

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    The new engines would have to real hemis. They could only get 245hp out of they're biggest motor(5.9l) before. Now it's 345hp with approx the same displacement.
     
  12. Lance Nichols

    Lance Nichols Supporting Actor

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    To simplify the above jargon... [​IMG]

    A Hemi is Chrysler/Dodge/Plymouth's (may they rest in peace) kick ass/'Stang/'Vette monster engine. Rare birds, any car with a 436 'Hemi in it was flat out a race car with street steel bolted onto it. The (426 version)engine is bullet-proof, and is still being produced today, either by Keith Black Racing as a Drag racer's dream, or as a MoPar crate motor.

    The New Hemi's will be found in Dodge pickups (replacing the v-10s), Chrysler 300m, and Dodge Magnums. Rumours have a MB running with it as well. 5.7L sounds big, right? Nope, only 350 CID. The HUGE Viper V-10 (8L) was "only" 450 CID...

    Still, even though my favorite current MoPar is my GT Cruiser, the 300m and Magnum sure look nice...
     
  13. LarryDavenport

    LarryDavenport Cinematographer

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    Semi-related, what is a "glass pack" and what does it do?
     
  14. Bryan_K

    Bryan_K Stunt Coordinator

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    " man police... Put you male card on the sidewalk.... Good ...now walk away....S-L-O-W-L-Y" [​IMG]
     
  15. Alex-C

    Alex-C Screenwriter

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    sweet!
     
  16. Lance Nichols

    Lance Nichols Supporting Actor

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    Larry, a glass back is a muffler packed with fibreglass, and traditionally is a straight flow unit.
     
  17. Steve_Tk

    Steve_Tk Cinematographer

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    So what kind of gas mileage does a hemi get?
     
  18. Blu

    Blu Screenwriter

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    Is it just me or has the economy phase Americans were going through for a short while over with in exchange for more power and faster street speeds?

    I would love it if this was going to be the second coming of the true muscle car.
     
  19. Todd Hochard

    Todd Hochard Cinematographer

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    We're getting both. Consider the now-discontinued 2002 Z28. 320hp from the factory, but most are putting almost that to the rear wheels, and you can knock down nearly 30mpg on the highway in one of these. The past couple of years have put out some fantastically powerful cars.
    Personally, I think the horsepower race is getting to the stupid level. I think a bigger focus needs to be put on efficiency. Not, mind you, at the expense of current power levels, but simply "cap" the power levels here, and begin pushing the envelope on efficiency. It would appear that many of the car makers agree with me. Look to see 6-speed autos with DEEP overdrives, cylinder deactivation on 6 and 8 cylinder cars, and hybrid tech getting into "regular" vehicles (specifically motor assist, idle-off, and regenerative braking). Current vehicles are only about 20% efficient, in terms of the energy they take from the fuel, so there's plenty of room for improvement. And, the past 25 years have shown us that power and efficiency go hand in hand.

    Todd

    P.S. Look for a 250-260hp 3.0l V6 Accord that gets 29/35mpg later this year.
     

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