Hemi this hemi that :D

Just wonder for those of us born post hemi era, I've heard two things, it's a block or it's a air intake system. Any details?

Its the head.

hemispherical combustion chamber... and something to do with splayed valves. 'course they don't say that damn near anything thats DOHC /w 4 valves/cylinder has a pentroof design... which is damn near the same thing as a hemi.....

its just a overrated name

Originally posted by braxton357
Its the head.
yup with the spark plugs up top in the center of the head

one question I always had (never pulled one apart) but is a 3.4l toyota motor a hemi?

Originally posted by Impulse Taco

its just a overrated name

Eh, debateable. The current stock certainley, but I've a softspot for the 426. Which is what the marketing dept at DC is hoping folks will identify with.

akin off the dodge website


"In a HEMI engine, the top of the combustion chamber is hemispherical. In a HEMI head, the spark plug is normally located at the top of the combustion chamber, and the valves open on opposite sides of the combustion chamber. The chamber creates and holds most of it's heat that creates pressure that gives it it's power, compared to ordinary flat block engines found in many automobiles today. Another factor with a HEMI head is the size of the valves. There are more room for valves. In a HEMI engine, valves can be large so the airflow through the engine is improved. "

Not takin from a website.
The intake and exhaust are normally 180* top to bottomfrom each other, rather than side by side. the straight exhaust ports to the exhaust manifold is straight instead of a short fast curve, which slow the flow coming out of the head. straight through is the path of least resistance. Most motors in order to get a pathway even close, you have to spend extra money on new heads that will have somewhat straighter exhaust porst coming from the head, and noramlly longer. but the valves are still no inline with eachother so there is still a resistance in flow in the head. Whick is why they started getting into heads with a swirl style combustion chamber to driect the flow of the burnt fuel and air to the exhaust valve. which take up energy to do this.

edumacation (http://auto.howstuffworks.com/hemi.htm)

It's almost odd to me that people don't know this. :confused:

Kinda like not knowing what posi-traction is or what TPI is.

Here's something: NASCAR went a long way to hindering US manufacturing technology. They got rid of the hemi because they dominated.

NHRA is pretty bad too.

.

The Mitsubishi 2.6L I-4 used in K-cars was also a Hemi-headed engine.

Low-point for American automotive marketing was when the Chrysler guys came up with "HEMI" badges for these cars that had "4 2.6" underneath.

Anyone else remember that marketing travesty in the late-80's?

It's a marketing ploy.









My 89 Honda was a hemi.

Originally posted by rusted

Here's something: NASCAR went a long way to hindering US manufacturing technology. They got rid of the hemi because they dominated.

NHRA is pretty bad too.

One reason I hate NASCAR: they refuse to allow new technology. C'mon... Racing is supposed to be a hot-bed for new tech...

One *very* important point to mention, some debate the most important, is the position of the spark plug. Because it is centered (and not off to one side), you get a greater burn percentage because the flame doesn't have to travel as far as in a normal engine.

its like a honda motor.

Originally posted by BobBarry
The Mitsubishi 2.6L I-4 used in K-cars was also a Hemi-headed engine.

Low-point for American automotive marketing was when the Chrysler guys came up with "HEMI" badges for these cars that had "4 2.6" underneath.

Anyone else remember that marketing travesty in the late-80's?

*wincing*.... Thankfully, no

Originally posted by briscoekid
its like a honda motor.


Hmm not exactly...that would be a pentroof design. Not the same as the legendary hemi. Which had to go away bc of greenies and emission policies.:rolleyes:

:edit: well..it may not have been greenies, but Im gonna blame it on hippies anyway.:flipoff2:

Originally posted by rusted


Kinda like not knowing what posi-traction is or what TPI is.



TPI = threads per inch.... oh what what was that other thing? :flipoff2:

Worst one...

EFI for COMPUTERS.... Extensible Firmware Interface, yep the replacement for BIOS. I do wonder if that Intel Engineer is a gear head who slipped to his boss "OH, I'm working on my EFI system" one day... and had to come up with a name! :D

Grew up in a "Chrysler" family. Wasn't considered a real engine unless it was a Hemi. Hemi, v8, slant 6.... in the family. I swear that Slant 6 is still running someplace.

Tom :usa:

Originally posted by GRMhick
one question I always had (never pulled one apart) but is a 3.4l toyota motor a hemi?

we took one apart in class,



can you say HEMI?

Originally posted by dieselcruiserhead
Hemi this hemi that :D

Just wonder for those of us born post hemi era, I've heard two things, it's a block or it's a air intake system. Any details?

Ok the bell is about to ring for 4th period.....better run along. O'm also not so sure that PBB is ok for the school libray computers.....have to talk to the librayian about this.....


Hemis are great for forced induction dragsters on methanol. Pent head is better designe for DD. It was a great motor in the 60's and 70's but now it's overrated like the Vtec. :D

TPI= throttle port injection

I didn't read each post:rolleyes:

Has anyone mentioned anything about a "shotgun hemi"

This is what they called the Ford Boss 429 motor, because it had a hemi head but a flat piston.

Therefore the combustion chamber was not a "true hemi"

My wifes 98 Hyundai Elantra is a hemi.
Many new cars are.

The first hemis that I know of where Chysler prior to the 426.
It was a 392 I think, they had several sizes in the early 60's, maybe late 50's.

I looked at a Mondella (sp?) drag boat that had one it back in the late 80's. 196?, wooden hull, 392 hemi V-drive, owner claimed that it would do 140 in a 1/4 mile. I seriously doubt it, because he was a major windbag.
I doubt it would do over a 100 in any distance.

Originally posted by rockota


One reason I hate NASCAR: they refuse to allow new technology. C'mon... Racing is supposed to be a hot-bed for new tech...

Why do they need new technology? They already have to do things to keep the freaking speed down with what they got. They are at the limits of what the tracks will take. Your also talking about raising the operating costs. This is exactly the reason F1 started putting restrictions on stuf starting with the tire size a few years back.

Same thing that happend to IMSA. They were going faster then the tracks could safely handle. The made them open cocpit to creat lots of drag and slow them down.

Now if fawking NASCAR would alow freaking windsheild wipers and rain tires I would be all for it and stop this crap of not racing in a full body car when F1 is still hitting 200mph in anything but the worst rain.

This (http://www.greatlakesdragaway.com/video/hemivsvet.avi) and this (http://www.greatlakesdragaway.com/video/hemiglass.avi) and this (http://www.greatlakesdragaway.com/video/redvshemi.avi) is a HEMI :D

A true Hemi has a nearly Hemi-spherical combustion chamber (hence the name). Few engines are true hemi's, and no modern engines are true hemi's.

What is/was good about a hemi combustion chamber?

A hemi chamber allows the valve stems to be canted at an angle to each other, providing for larger valves and ports and a less restrictive intake and exhaust port design. These advantages allowed the historical muscle car hemi's move more air and make more power than their competitors. Chrysler was the most recognizable hemi producer (displacements from 292-426ci). The Ford and Chevy big block's canted valve heads were attempts to gain some of the hemi valve and port size advantages without building a true "hemi" (without running contrary to NASCAR rules, until NASCAR limited displacement and closed the loophole).

What is/was bad about a hemi combustion chamber?

A true hemi chamber needs a tall domed piston to achieve a reasonable combustion chamber compression ratio. This tall piston dome gets in the way of efficient flame travel (demanded for clean emissions and superior power at high rpm). Ignition has to travel from the side of the chamber with a spark plug to the opposite side of the piston, with the tall piston dome in the way. Higher rpm operation is limited by the time it takes for the flame front of combustion to occur, as it has to travel the length of the dome to fully burn the intake charge. The large dome also makes preignition control difficult (pinging, because of the ignition advance required). From a power aspect it was not very significant with a large piston bore (with a 426), and with high octane fuel, but the poor burn control could not produce clean emissions in a production car (even with dual plugs and electronic ignitions to bandaid the drawbacks).

There are 60' era "hemi" advances that partially resolved these problems. Ford's SOHC 427 was more of a combined hemi/polysphere chamber demanding less of a piston dome, and the Boss 429 was an improved version of the same technology with no piston dome. The ironic thing behind the superior Ford "hemi" head and piston designs was Chrysler pioneered polysphere chamber technology in the 50's when they offered a choice of hemi or polysphere heads on 292/318/361 blocks.

Two improvements occured is engine design since the 60's (and the famed 426 hemi): designers realized the intake and exhaust charge needs to travel down the cylinder to fill the displacement (turbulance down the cylinder is beneficial), and the combustion chamber at ignition is a three dimensional volume that includes the piston dome (a good unrestricted central initial charge shape is beneficial).

A true hemi head flows air efficently from intake to exhaust valve, but not too well down the cylinder bore (much of the bad charge from the previous exhaust stroke remains at the bottom of the cylinder, and some of the good charge is prematurely sucked past the exhaust port). A true hemi has the big valves but the tall piston dome results in a funky sectional chamber at the TDC igniton (not a tight densely packed charge that is well shaped and easy to spark, something that is obvious to a demolition specialist). There were quite a few of these port and chamber design advancements in the smog-law 70's that have only shown up in production engines during the last ten years.

Most modern two-valve and three-valve "hemi" engines use modified polysphere combustion chambers (automotive and motorcycle) and the spark plugs are still offset (or they run dual plugs).

Most four-valve "hemi" heads are actually modified pentroof designs, with the valves shaping the chamber more than raw chamber machining. Four valves allow for a central plug placement that eliminates some of the flame travel problems.

Regardless of the design, old school and new school, if you want to go fast, it's all about regulations and money (even with the modern "hemi").

Happy Trails!

Firepower head from a '56 New Yorker;
http://webpages.charter.net/w01845730/pictures/firepower.JPG
http://webpages.charter.net/w01845730/pictures/hemivalve.JPG
http://webpages.charter.net/w01845730/pictures/hemi1.JPG
Factory dual quad intake from a '54 Chrysler 300;
http://webpages.charter.net/w01845730/pictures/300intake.JPG

The Chrysler Hemi started as a 331 in 1951, went to 354 then 392. There were also smaller versions, the Desoto Firedome and Dodge Red Ram. 1958 was the last year for the iron Firepower style. It was too expensive to manufacture, and was replaced by the polysphere head on the same block. The basic hemi design resurfaced in '63 on the 426 for racing, and later muscle cars.

Originally posted by 2stroke
TPI= throttle port injection

TPI= TUNED port injection :flipoff2:

TBI= throttle body injection

Watch Joe Dirt!! Classic. Whenever someone says Hemi, I am reminded of that.

The motor I am running is called a japanese hemi or something from memory...... Jap V8! mmm !!

Heh heh, my wife's 1.8l Passat is a hemi.:laughing:

"Hemi" started in 1955 with Chrysler/ Dodge hemi-head-----(Dodge Red Ram)
multiple valves per cylinder is nothing new----1931 !LaSalle
multiple spark plugs per cylinder------1928 Cord/Rolles/Stutz
retractable hard top convertible------- 1917 Peugot

Nice to come back and see some action on this thread... Damn straight I know about TPI TBI Vortec and positraction :rolleyes: just didn't know 'exactly' what "Hemi" means PS also watched Joe Dirt tonight again ;)

Thanks for the edjumaction boys :cool: