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Hemi
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Posted by: 02TRANSAM02

what is the difference between a 440 and a 440 hemi

Posted by: MikeT

hemi was a 426

Posted by: 02TRANSAM02

oh i thought i heard something about a 440 hemi? oh well i'll reword that whats the difference between a hemi and a normal engine

Posted by: MadScientistMatt

There are a few 440 Hemi's, but they didn't leave the factory that way; they are 440 Wedge motors with aftermarket cylinder heads based on the 426 Hemi heads attached. There were a few other Chrysler Hemis out there, the most well known being the 392 and 354, and Hemis from a few other companies too (mostly imports, including a Toyota V8 not sold here and the 2.5 V8 in the Daimler Dart). Most of the non-Hemi "traditional" American V8's since the '50s have used "wedge" combustion chambers.

The difference is in the combustion chamber design. To get the idea of what a "wedge head" combustion chamber looks like, imagine a somewhat flat bathtub, with a tilted floor. Now imagine two enormous drains with pop-up style stoppers in the tub that occupy pretty much the entire floor of the tub. The valves don't look quite the same as pop-up drains, but they work in a very similar way. And, of course, this bathtub is only about 4" long. To get air and fuel into a wedge head, it has to come in at right angles to the combustion chamber floor, make a 90 degree (more or less) turn, and come in through the valve. When the exhaust comes out, it makes another 90 degree turn and exits the other side.

Now, a Hemi head is more like half a baseball. The valves are on opposite sides of the combustion chamber. The air coming in and going out has close to a straight shot through the valves instead of making a turn. In practice, the hemishperical shape is flattened a bit and the air has to make something of a turn. But it's still a bit easier to get air into and out of a hemispherical head. To get the same straight shot into and out of a wedge head, the intake and exhaust manifolds would have to point almost straight up on a V8 engine, which would make for an awkwardly large motor.

There are a few disadvantages of Hemi engines. They often have emissions problems, and the hemispherical combustion chamber makes it hard to get good compression without enormous piston domes. They're also a bit more expensive to make.

BTW, there are also combustion chamber designs commonly known as "bathtub-shaped" combustion chambers. These don't look like the wedge chambers I described here. Even though I think the wedge chambers look a lot more like bathtubs than most "bathtub-shaped" chambers I've seen, that's what they call them.

Posted by: 02TRANSAM02

thanks matt but one more thing i saw a hemi cuda ('70) go for $70,000. is most of that money for the motor or the car?

Posted by: StoneFox

It went for that much money because it is a very desirable car, All of the numbers match (all original) and very very well restored.

Posted by: MadScientistMatt

Well, the best way to describe the costs is that the buyer is paying for the originality and the history that goes with it. A brand new Hemi can be had for around $10,000. A decent Barracuda can certainly be had for less than $20,000 (the cost of those is higher than just about any other '60s or '70s Mopar, though) and it isn't too hard to put it in there. However, an original Hemi Cuda is more than just a car and an engine. It's a survivor from an era that is now long gone, that embodies a large number of things that were good about that era.

Posted by: 02TRANSAM02

oh ok cool

Posted by: DeckSetter

Well said Matt

Posted by: RacingJason

You forgot to mention that N/A cylinder filling in a hemi motor stinks. That is why it is common to see a 50% power gain when a mild blower is mounted on a Hemi...and SVT cobra owners thought their engines loved blowers!

Don't forget to mention the semi-hemi (shotgun Hemi) Boss 429 motor too, that really ran piss poor in N/A street trim.

Posted by: BigBluOx

Didn't Ma Mopar make a Hemi 6 also? I seem to recall hearing something about those (mostly in other countries like Australia)...

Jon

Posted by: MadScientistMatt

The Hemi Six was a motor that showed up in Australian Valiants. The cylinder head is very similar to the other Chrysler Hemis, but the engine has no parts in common with other Chrysler motors. I've heard it's nearly impossible to make one share the same engine comparment with a US-spec steering box.

Posted by: The OLE MAN

Quote:


	Originally posted by RacingJason You forgot to mention that N/A cylinder filling in a hemi motor stinks. That is why it is common to see a 50% power gain when a mild blower is mounted on a Hemi...and SVT cobra owners thought their engines loved blowers! Don't forget to mention the semi-hemi (shotgun Hemi) Boss 429 motor too, that really ran piss poor in N/A street trim.

WELLLLLLLLLLLLL, O.K. I'll agree about the blower stuff. BUTT, the HEMI does run VERY well with alot of COMPRESSION also.

The OLE MAN

Posted by: RacingJason

I wouldn't want to line up next to a wedge motor that had some nasty heads with a Hemi...I have owned a few of them and they do run well in N/A high compression trim, but give me the wedge motor if we are talking no superchargers allowed.

Ole Man...you should have seen that last set of MP Hemi heads I sold. They flowed enough air for 2 big blocks!! The guys at TEA were glad to see them leave!!

Posted by: casey5

i pondering whether ornot to get stage v hemi conversion heads for a 440 im building. they cost like 2 grand assembled.:bananafuc

Posted by: fly

Quote:


	Originally posted by MadScientistMatt The Hemi Six was a motor that showed up in Australian Valiants. The cylinder head is very similar to the other Chrysler Hemis, but the engine has no parts in common with other Chrysler motors. I've heard it's nearly impossible to make one share the same engine comparment with a US-spec steering box.

that was almost correct.... the aussie hemi 6 shares nothing in common with any american engine except its name. this engine does not have hemispherical combustion chambers. The name was just a sales ploy... And correct, no parts are interchangeable with that era's mopar \6. This engine was impressive though. One factory configuration included triple webber side draft carbs and produced over 300hp. This was an option only in early 70's aussie chargers. This car held australian factory performance records for 10-15 years. I have heard mixed stories about whether or not this engine will fit into an american engine compartment... but have yet to see why anyone would bother.

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