last night at my college Bob Lee, the guy at the head of the new hemi project gave a talk about the new engine.

first off, this engine from my perspective has alot of possiblilities. the intake and exhaust runners are really really nice and straight.

also he claims that the engine will not leak anything. it was designed not to. so we will see about this. and in all of their tests it shoudn't leak.


according to him in all of their test the new hemi will last 150,000 miles for 95% of units produced.

anyway, in his talk he referenced the old 426 hemi in the design of the new one. he said that the old hemi, while good had alot of problems with size and combustion chamber.

he stated that the sound of the idle of the 426 was due to poor flame propagation. and from a technical drawing i can see why.

the pistons were big and heavy, and the intake and exhaust runners were of poor design.

Now mind you this is what a Dodge engineer was saying. and i am sure he has the test equipment to back his claim.

now why was the hemi so popular if such a poor design? why do the dragsters use it extensively?? if you were to take and lower the compression do these heads just flow insane ammounts of air?

other than the nostalga of the engine, what was so good about it?

later

andrew

 

Two main reasons:

1. Spark plug location.

2. Also, because the chamber is hemispherically shaped, you can fit larger valves without having the shrouding problem common with conventional style chambers - better flow

 

Yep. Ideal plug location (power and detonation resistance), good flow. The intake and exhaust are just about opposite eachother in the combustion area so it's almost a straight shot flowing air through the motor, with a piston in the middle!

It's a GREAT design for racing. Flow = Winning Races. Top fuel cars still use a design that can be traced back directly to the 426 Hemi.

FOr a street motor that lives most of it's life at part throttle and moderate RPMs, not so great. It's kind of a "drity" motor, emissions-wise, too.

I'm sure there are others who know a lot more about the Hemi than I do and will post.

 

Good article on it in the new Hot Rod.

 

Chrysler wasn't the only one to produce a hemi. Many import engines use a hemi design with the spark plug at the top of the cylinder. Ford produced a hemi. Harley Davidson finally went away from the hemi in 1984 when they produced the first Evolution engine.

 

Also, doesn't the hemi- heads reflect all of the explosion energy of the combusted fuels parallel to the cylinder wall, making a more efficient power stroke? I would think this is the case since the combustion would be completely directed perpendicular to the piston head.

 

Is it going to be a true hemi or is it going to be a pentaroof?

 

That's because most imports have OHC. And spark plugs in the center of the chamber is not just restricted to import OHC, domestic OHC's are the same way.

 

The "new" hemi is only a 5.7L engine also. Not much in common to the old 426.

 

The thing about the hemi design is flow... it's a nearly straight shot through the cylinder. It has nothing to do with "reflecting the energy", since the thing that produces power isn't an explosion, it's a smooth controlled burn that increases the pressure in the cylinder. In fact, "explosion" is considered undesirable, it's usually referred to as "detonation", and is avoided since it causes parts death. This type of engine is a "heat" engine, not an "explosion" engine.

Nearly all of the multi-valve motors have some degree of hemi design to them. DOHC lends itself to that, since the 2 cams have to be in different places anyway; one for the intakes and one for the exhausts, with the cylinder roughly hemispherical in shape and the spark plug right in the middle at the top, is the simplest way to design one.

 

the chamber design, hemisphere, has the largest volume with the smallest surface area. So the heat is forced to move the piston more than be lost through exposed surface area. Plus the design allows for more optimal placement of the valves and sparkplug.

I'm sure one day the flathead will make a comeback as well

 

Yeah but it sure does look like Chrysler really did their homework on them this time! The old Hemis were inefficient in how they used fuel but these new ones are about as clean and efficient as a whistle.

If they would come out with a new 'Cuda or Challenger with these 350 Hemis, I think a lot of folks would be lining up to grab one

 

Well I never thought I'd hear any mention of the hemi on this board.
I'm an AMC lover at heart and big mother mopar is my other love.
Listen all the hemi is is an R/B block which for those of you who don't know what that is that is the raised deck platform that the 440 was built on.
The 426 just has relocated coolant passages and reinforced four bolt mains. of course there are some other little variations like different motor mount locations but that's irrelevant.
The hemi made so much sense considering it's a straight shot from the intake to the exaust valve.
The new hemi I can't say much about due to the fact I have no experience with it but one thing I can say is that it's gonna be real sweet.

 

yes the new design really has almost nothing in common with the old hemi other than the concept and the name.

angles are different and stuff. i really want to see how good this engine lasts. it looks to be a VERY VERY excelent design, at least on paper.

as far as i know it is a true hemi.

 

the 426 hemi despite being somewhat sloppy of an engine produced rediculous horsepower.. thats why people like em... although advertised as 425-430 horsepower range if you were to take an actual 426 hemi and put it on a engine dyno you will yield results much much higher.. upwards of mid to high 600's in some cases.......

 

For your original question, the reason they became so popular was in the early 60's the first three hemi engines won the first race they were ever entered in. The three cars took first, second, and third--a clean sweep--and the legend was born.

A couple years later the hemi made it onto the streets with a similar setup (they were lighter and made more durable for everyday use), but still had more power than anything else. The 66-69 Hemi Cuda 440 engine is still one of the top 5 stock engines ever on street w/o any mods. That is why they still are on the strips today, some nostalga, mostly performance.

Jm

 

the 426 Hemi wasn't even Mopars top motor, it was the 440 Six Pack. There were however a few stock (made for race use only) kick *** hemis made that would kill a 440

 

nah 426 made more hp and torque...440 was a later engine.. just more cubic inches with less compression and heads that didnt flow quite as well...like a quarter the size of the 426 heads too hehe

 

oh and by the way.. look out in 2006, hemi dodge chargers are comin back.. lil hemi tho.. only a 6.1 hehe

 

I was told by an engineering teacher the 426's Hemi's ability to make useable power was reflected in the shape of the combustion chamber itself. he said that an "ideal" combusiton chamber would be the shape of a triangle, with the plug at the very top in a direct point. obviouselly, for parts durability reasons, a piston with a sharp point on the top isnt the best idea... But the Hemi apparently comes close.

I don't remember the whole conversation, but I DO remember somthing about cramming more fuel/air into a smaller area, easier, etc. etc... then useing it more efficiently etc etc...

 

Spark plug location....valve size....engine cubes and the extirior look of it,and they have really crazy looking rocker arm set ups!

 

I just bought a car about 3 months ago and had it 3 day before the motor threw a rod (i got screwed) but to the point it was a Ford "Hemi". Most dont realize but the 2nd body style Taurus SHO has Yamaha Aluminum Hemi heads and they make some great power. My 95' SHO 5speed would outrun my LB9 GTA A4. But as a typicall ford it didnt last. But the spark plug location made for an almost complete a/f mixture burn in return made great power on the SHO.

 

Hey, heres a little tidbit I bet most of you don't know... Chevy almost released a "Hemi 302" for the Z/28 in 1969! It had aluminum heads (hemi obviously) with rediculously large valves. Wasn't put in production though... cost way too much to make them, as it required really complex head designs and a modified block so the pushrods could be routed differently, and used a different exhaust manifold design IIRC.

The Hemi really is only a better engine than say, a 440 or a BBC, above 4500 rpm. Thats because the combustion chamber design had a very good surface area to volume ratio, and with the rediculously large valves (2.25"int / 1.9"exh I beleive) it could breathe MUCH much better than a more conventionally shaped chamber. Also, the shape of the chamber forced more of the power from combustion straight down onto the piston, instead of letting it dissipate in all directions, like the normal designs of the time.

At low rpm, however, it was a very dirty running engine. It was far worse than something like a 440 or a 454. It was not really because of the cam or anything like that (although they were pretty wild), but because, IIRC, there was just too much breathing capacity for the engine at low rpm... the valves were gigantic, the ports were almost big enough to walk into, and it had two 650 cfm 4bbl carbs sitting on top.

Before all the new laws were intorduced, there was even plans for a 426 Hemi engine in the '71+ R/T cars with a 6-Pack manifold. It was basically a slightly modified 440 6-Pack manifold, made to work on the Hemi.

This is why it was shut down mid way through 1971. Mopar was too proud of this engine to let the government strangle it with new emmitions laws (which is why it kept its 10.25 CR when others dropped to around 9:1 or less) and the engine was just way too 'dirty' to pass for legal with any of the new laws. Even in 1970, the 426 Hemi did ALOT worse for emitions performance than even the LS6 (454ci/450hp) or the Boss 429.

Oh yea, just remembered... thats also why the Boss 429 Hemi was discontinued as well... it did almost 2X worse than the regular Boss 429 for emitions performance.

I gotta agree though... those Mopar Hemis really look hairy... and this thing is about as hairy as it gets... :hail:

 

Sure, go get in line for one.

 

Just to comment on that....yeah, Chrysler engineering sucks! I never thought about it, but I couldn't COUNT how many Chryslers I've seen running around barreling smoke. My friend's mom had a LeBaron with maybe 60,000 miles or so on it and it never ran right. Leaked oil out of every seal you could think of..started burning it....ran like crap. Was in for servicing a dizzying amount of times. At least the car got a fast and respectable death (collision).

 

does anyone have a hemi in a 3rd gen??

 

That is blasphemy! Bastardization of a third gen is strictly prohibited!

 

V8 is V8 it doesnt matter who makes it. Mopar is a respectible DOMESTIC company. Its not like i'm asking if anyone dropped in a VTech ford V4

 

Point noted...still though, for simplicity's sake, I dont see why you would. Except to be a showoff or have something very very cool. Mopars are too expensive to build anyways... SBC's are the best because they're cheap as hell. Even cheaper than Ford smallblocks. I know, I own a Ford smallblock!

 

well you do have a point there. I always wanted to say "I got a Hemi" owell

 

I started with a V6. I always wanted to say "I have a V8." Then I had a 302, and I wanted to be able to say "I have a V8 with heads and a cam." Now I have a V8 with heads and a cam, and I want to be able to say "I have a 347 stroker". Then I'll get a 347 and I'll want to be able to say "I have a nitrous-injected 347 that runs 9's in the 1/4".... The cycle never ends. It's vicious. Get out while you still can!!

 

302?? you have a FORD V8 in your car????? (or did you mean 305?)

 

See signature below.

 

OHHH............. your sold your camaro to buy a PONY???? ok that is blasphemy! Bastardization that is strictly prohibited!

 

Hey, that's not bastardization, that's just being a traitor. Get it straight. Hey, you should've seen my face when I started the car for the first time. Running headers, X pipe, Flowmasters. No cats, with dumped exhaust. I deafen bystanders and set off car alarms. Would you really turn that down for $3000? I couldn't. Wish I didn't have to sell my Camaro to keep it, but...that's the way it goes. I also wish I would've known that that $3000 pony I bought had a bent connecting rod...hence, the crate motor. Still, it ran 14.5 at 95 with a bent rod and burning 3 quarts per oil change. Can't beat that with a stick.

 

Mustang are RWD and domestic so i dont have any beef with them

 

I don't knock the mustangs either, I used to own one, I had fun with it like I do the T/A now. And don't forget, if it weren't for the mustang the f-bodys wouldn't exist. The rivalry makes both camps better.

 

Well, the rivalry DID help. Chevy needs to come out with another pony car. And not the SSR, because....no. That's no help.

 

i was putting some real thought into this and i was thinking could i buy a normal v8 maybe off a dodge durango and then when i have fit everything and cleaned and rebuilt the block i could slap on does hemi heads? does anyone know if that will work i'm not exactly an expert on mopar

 

Sorry, people, but it seems we've totally diverted from the "ThirdGen F-Body Technical" requirement for threads. Read the rules...