Why is the Chrysler hemi-head engine the best V8 ever? - Moparchat

Reasons the Hemi is superior!
higher compression ratios can be achived
because during Valve overlap(the point in the valve timing when both the intake and exhaust are open at the same time) the cross flow across the piston is almost ideal in its path.(ie the flow path is straight because the valves are in line, not next to eachother)
It also can handle more compression than any other head due to the surface area in the combustion chamber. The more compression the more heat will build up on the surface.
The more surface the greater the heat dispersion.
The surface area is also cooled by the mixture that flows through the cylinder during the overlap phase of the cam cycle. And because the superior design, the Hemi flows more and cools more during overlap than any other design.
The port design (aka not a Siamese design) is easy to modify and limited only by water passages and oiling passages instead of the normal wedge designs that are limited by the port right next to the one you want to modify.
It also has an advantage that when you set the timing it requires less advance than any other engine type, this is partially due to the location of the spark plug in relation to the valves.
The flame, when created in a hemi piston starts in the middle, wedge and canted valve motors, because the sparkplug placement, have a flame that spreads unevenly across the piston surface. this is due to the sparkplug being to far to one side of the piston. this "feature" has been improved with canting the valves and modern flow dynamics. But this only serves to make the motor more hemi like, without being a true Hemi.
The Hemi block as cast by Chrysler also featured Crossbolted mains and a Nickel/Iron block. Both features you could not get from GM or Ford unless you were ordering the motor in parts,over the counter. If at all.
The Rod Ratio in the Hemi was and is far superior to almost all other BB motors built. No motor beats it, the best others can get is to be as good as, but never better.
The crankshaft/pistons from the factory were all forged steel pieces.
An almost unheard of thing when you talk about GM or Ford motors.
The only real downside is the weight of the piston(due to its shape) and the stock exhaust rockerarms geometry is supposed to be a little shaky when you are dealing with a non-stock racing motor.
The fact that the shape of the piston detracts from the fuel flow around its surface. A flat top piston is best for fuel distribution around the piston surface.
There probably is more to it, but that is all I know.
Maxwedge


[This message has been edited by Maxwedge (edited February 08, ).] I dont know of any motors that while naturally asperated, and using stock bore and stroke making 800 hp like Ray Bartons hemi's.
That was not a typo.
sorry but we shal disagree on the Hemi being archaic.
If it was such a bad design, and old, why is it still banned in some classes,
why is it that the motor holds most of the salt flat records for supercharged and naturally asperated Piston motor records??
Why is it that in tractor pulls, if you run a class with 4 motors being the standard IF you are running an Arias(I hope I spelled that right) Hemi Head(which is Exactly like the Old Chrysler D-4 magna head, with the exception on the raised D-shaped exhaust Port) that with a motor with that head, you are Required to run One less motor than the rest of your competition???The reason is that even if you are running less motors you (the user of the Arias motor) still beat alot of the competition. And it is proven to beat everyone if given the same number of motors as the rest of the competition.
and why is it that no one has yet designed a better motor for the Nitro classes???
Indy cylender heads, has a motor that at I believe(I could be wrong on eact size)510ci hemi with a freshly designed Hemi Head(they canted the calves 2-5 degrees) that with 16:1cr and 2 Bg carbs put down hp...
but the motor costs 15k...go figure..
I think the wedge motors do have an R+D time edge over the hemi's and therefor have Clutches and chassis better suited to there needs
Oh and I do appreciated the information on the NHRA stuff..

Maxwdge

[This message has been edited by Maxwedge (edited February 10, ).]

[This message has been edited by Maxwedge (edited February 10, ).] Y'all quit picking on DartGT66. Just because we love the Hemi doesn't mean we can't recognize its faults. He makes some good points. There are disadvantages to any engine design and the disadvantages of a pushrod Hemi include heavy valve train and heavy pistons and probably the other things he mentions. Of course, there are advantages of a pushrod hemi vs. a pushrod wedge, as all of you have noted, including better flow and better thermal characteristics. However, it is true that at the moment you can build an unblown gas big block wedge motor that will make more power than any naturally aspirated gas Hemi motor. That's not just me or DartGT66 talking, that's the company that makes aftermarket heads for both types motors (Indy). I think that state of affairs is primarily a consequence of virtually no development of the Hemi outside of top fuel classes for 25 years, but nevertheless it is a fact.

It is also true that there has been virtually no development of Hemis for 25 years because NASCAR, and NHRA in the Pro Stock classes, for all practical purposes outlawed them in the early 70's. At that time, Hemis flat dominated the competition. Big block Chevies could not compete with the Hemi in Pro Stock, and the Fords couln't compete heads up with the Hemi in NASCAR. Where the Hemi could be today with 25 years of development of the basic design is something we can only guess at. I think its advantages over the wedge would outweigh its known disadvantages, but of course this is just a guess on my part.

But it's also true that, all other things being equal, a double overhead cam, 4 valve pent-roof motor will make more power than a two-valve pushrod hemi. Whether a 4 valve head would be any advantage in top fuel racing is debatable because these cars already make more power than they can use. I've also read that 4 valve motors don't have that big an advantage over 2 valve motors at very high lifts. But certainly in any kind of streetable motor, a 4 valve motor will make more power simply because it breathes better, and an overhead cam motor has less valvetrain weight and will rev higher than a pushrod motor, especially one with rocker arms as long as a pushrod Hemi.

By the way, Chrysler had plans to develop an overhead cam Hemi if NASCAR had approved Ford's 427 cammer hemi for . NASCAR decided that its racing motors had to be built in quantity and available to the general public. When Ford decided not to produce its cammer hemi in quantity, Chrysler dropped any plans to make its own overhead cam hemi, but did introduce a pushrod Street Hemi for the model year just to legalize the Hemi for racing in NASCAR. The reason why Hemi makes good power in super stock is that it has the right things for the class, big carburation, well flowing heads and high compression ratio. Everything else is custom and they make good power.
Other manufacturers do not have packages like that. Except one, that is AMX 390 in SS/C. No Hemis can touch one in that class, it's a pretty similar package to the Hemi Barracudas/Darts with cross ram intakes and two carbs, but regular AMC wedge heads and runs low 9's.
The Hemi isn't slouch, but it should remain as a legend and not compared to the newest technology pushrod engines; it was originally designed almost 50 years ago and during that time a few things have happened.
One reason why the Hemi is widely used in very high horsepower application is not it's ability to make better power than some other designs for example in tractor pulling, but its extremely strong bottom end that stays together better than the others.
The Hemi was banned in Nascar, but not in NHRA competition, the four valve heads are not allowed in fuel or alcohol classes.
In the sixties, When Chrysler first reintroduced the Hemi, then Ford the Cammer and Chrysler started to develope a four valve headed engine, they had actually two different styles under developement; one was a dual overhead cam version and the other a single cam pushrod four valve engine with the cam in very high position in the block and short pushrods. I don't know how far that engines developement went, but I think there was working engines made.
The last step of the Hemi was in the late 60's, early 70's when Chrysler was planning to drop out the wedge completely! The new engine would have been based on a 400 B-block, and have been offered with new Hemi heads in 404 and 444 sizes with the old crank strokes, but both in a low block. The head bolt pattern was the wedge pattern and therefore the intake ports were not as straight as in the 426 Hemi and the intake ports flowed slightly less. However, the flow relationship between the intake and exhaust was better in the 'new' Hemi. The chambers were slightly twisted, maybe 10-20 degrees and unmachined as cast true Hemi chambers. The valve train was the 'chevystyle' ball & stud arrangement, and usually this engine is called the ball stud Hemi.
Because of the energy crises it newer made the production, but the plans were ready and there actually are some of these engines in existence. Dick Landy has one, for example, and my information in this matter is based on him.
However, back to the subject, NHRA Pro Stock. In the seventies NHRA brought some weight factors to different engines, and the Hemi lost its status. The cars became smaller and the chassis department less stock; that prefered smaller engines and the Hemi was incompetitive. Some people run small short stroke Hemis, but for a certain reason they were not competitive. However, it's a bit misleading to blame the factor; the BB chevys factor in the seventies was the same as in the Hemi, and the Ford Cleveland had even a bigger factor but was competitive. The wedges had a slightly lower factor than the Hemi and BB Chevy.
In the end of the old Pro-Stock small engine era, the Hemi suddenly was competitive again! So the development hadn't stood still. This was because the use of the 383 block that allowed lighter internals in the engine. Previously this kind of engines hadn't worked, but then someone figured out how the block could be welded reliably for the valley head bolt tubes and the exhaust pushrod channels.
Actually when the weight to displacement factored Pro-Stock ended, the Hemi held the Pro Stock speed national record; so, if you want you can say they banned it again when it was becoming competetive.
When the new 500 cu in engines came, at first there were several Mopar Pro Stock projects under work. However, they could not compete against the chevys and the ford(s?).
This was mainly because Chrysler did not have engine blocks the could be bored big; the displacement had to be found through long stroke while 'the others' had big over 4.5" bores and short strokes. One reason was also the shallow Y-block, that didn't allow good oil control which is critical to an all out naturally aspirated engine. The big bores allowed larger valves to be used in the heads and made the heads flow like in a Hemi.
There were still some courageous people trying to develope the Hemi, it was all that Chrysler had to offer at the time. In the same time The Ford Hemi continued winning, it didn't have the same glitches that the Chrysler Hemi had, it had big 4.9" bore centers that allowed big bores and short skirt blocks for wide dry sump pans. However in the late eighties even Glidden confessed that he had found the limits of the Hemi design, first the Chambers were modified to a lot smaller with smaller valve angles, and then he changed completely to the canted valve Wedge.
Koffels place was one place where they still made Pro-Stock Hemis. At the same time they developed a new wedge race head, the B1. Their first B1 mule made 60 hp more than their best Pro-Stock Hemi; that's a huge difference. After a couple of years they got a little back up from Mopar and went back to NHRA Pro-Stock racing, now with the wedge run by Wayne County and the driver Darrel Alderman.
Wayne County was well respected Pro-Stock engine builder; however they had been building chevys, not Mopars. At first, the B1 wasn't competitive, in the beginning they used the regular B1 wedge heads and the production blocks. When they got the second generation B1/TS head ready and the new Pro-Stock big bore center short skirt block, things started to happen. The rest you are propably aware of.
Now they are bringing the Hemi name back to the Pro-Stock. I say name, because there is nothing Hemi in the new engine. It's just the 'like everyone else' porcupine head with chambers twisted 90 degrees and a pretty strange port arrangement. Some people who really know these engines say that the way it is now it will never work. But the time will show...is anybody awake? The succesful normally aspirated Hemi engines use hand massaged pistons. It is very difficult to fill up those big chambers without taking a plug of them and having special pistons made up. Therefore it is very difficult to make high compression in a street or race Hemi head. The off the shelf 12.5 - 1 pistons usually fall in the 11.0 - 11.5 cr range. Ever really listened to a normally aspirated Hemi on gasoline? They do not have the pop of the wedge or cant valve motors. This is one reason why.

In addition, fill the cylinders with slugs for compression and you will block the airflow across the chamber.

Another issue with Hemis being top dog in today's world of ultra refined and massaged off the shelf heads is just that. Lack of R&D on the design due to either the ban or penalty issued in weight per cubic inch by sanctioning bodies during the 70's. It became more lucritive to test other brands and that is where the R&D of major teams went.

Take off the shelf head design from and the Hemi will rule. Take the same from and the Hemi is sucking hind tit so to speak.

Another problem with the street Hemi is reliability of the crankshafts. The undercut journals will crack under a build of power. I know. I threw away many of them. You need to find a Kellogg style crank for high performance.

Another issue as has been stated is the overlap at high lifts. You need to watch
it or the valves will collide.

Now why do the top fuel boys still use designs based on the 426 Hemi? There are
two compelling reasons.

First, the shape of the chamber allows for higher boost pressures befoe detonation sets in.

Second, the design of the engine allows for easy and quick teardowns.

One cannot build as much boost nor tear down any other currently available design as quickly as can be accomplished on a conventional designed fuel or alchohol Hemi. Think about it. The distributor does not need to be removed to tear it down. One can pull the intake and one head together if need be. Remove the rockers as an assembly and retorque them back without having to adjust the valves. Also the bottom end is very sturdy with it's deep "y" design and the cross bolts. Much stronger than that of a Chevy or Ford.

Jim Tatum


Actually there was an article in Hot Rod magazine a few years back where they built max 520 cu in pump gas engines. The Mopar wedge made the least power in dyno, 499 cu in and 736 hp, but was quickest in a car. All cars were same weight, had same gears & converter size, same exhaust size, same gas etc. The Mopar run 10.00 and had the best mph too, 134. The Chevy and Ford were in the 10.1-10.2's at 131-132 mph. There wasn't a Hemi in that race, but later Dick Landy built a pump gas Hemi for editor David Freiburgers Super Bee. It was a tad smaller than the wedge, 471 vs 499, had a little more CR and a bigger cam. It made more power in the dyno than the wedge, about 770 hp if I remember correctly, but the Hemi Super Bee was slower than the wedge Super Bee. The Hemi didn't have converter, exhaust or other limtations in the car; it run 10.6's at 125 mph after several tries. The car was in several build up articles in the magazine, and the last step of the series should have been the track test, but it was never published, propably because of the disappointing performance. DLi told that it was because of the low CR and the pump gas requirement, and there were some glitches in the intake design too. Freiburger now writes in the CarCraft, and I think the battle with the Hemi Bee continues on its pages, but I'm not sure. Anyway, that series of articles showed me that don't stare at the numbers produced by different dynos. The Ford had 820 hp, and the Mopar only 736 hp, but still at the track the Mopar made most power. The 511 Chevy made around 780 hp in the dyno but still had lower mph than the mopar. To be honest, the chevy run amazingly well considering it was a bolt on engine; the mopar and ford, and the Dli Hemi, was more or less hand built. There may be some fast Hemis around there, I've only got a wedge that has been basically thrown together. Without any tuning done I can duplicate the numbers made by the Super Bee in the Hot Rod article using DOT tires and a smaller exhaust, but my car weighs only lbs and the cars in the test were lbs. So far I haven't been outrun even by race gas burning Hemis, but on the day a pump gas Hemi beats me I may change my attitude.

[This message has been edited by DartGT66 (edited March 07, ).]

WO23Coronet   OP
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Canada Reading the other quench post prompted me to post a question that's always bugged me for a long time. I've learned through this forum that a short coming of the 426 Hemi's is that they are limited in N/A form when you start pushing HP to the limit, as compared to a more modern splayed valve engine (now I know that a HEMI can put down insane HP N/A, look at the Super Stock domination and so forth, I'm referring to Pro Stock and Pro Mod type engines so no haters please). I'm guessing the reason for this is that they have no quench in them and the insane piston weights that are needed to get compression. Why has no one "filled in" the sides of the chambers to cut down on the cc's and provide some quench, much like the Gen III hemis's, especially the 09 and later engines? Do Hemi's really need quench because of the centrally located spark plug? It seems that was the way that Mopar was going when they developed the Ball Stud Hemi in the early 70's (similar to a Boss 9 head, and we all know those things make serious steam)but I thought I would ask the engine builders and the Hemi guys on here because I'm just guessing.
Monte_Smith  
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The disadvantage the Hemi has is NOT from quench.......it's from terrible valve angles (for a naturally aspirated application) and piston weight...........and the ONLY reason Hemi's do well in Super Stock is because they have two carbs, instead of one like the Chevy's.....

Terrible valve angles...

2 carbs

In the last few years NHRA has allowed '64 Hemi cars to run 1 carb in A/stock as long as it's a NASCAR intake. From what I'm seeing they run pretty darn good for antiques.

Your carb answer is a moot point since they never orginally made any single carb drag or street packages and can't be proven.

It's proven everyday, on race tracks everywhere. The SS/AH combo is a bad hombre, don't get me wrong, BUT, if you let a 427 Chevy weigh the same and get a sheetmetal intake, with two carbs, you might be singing another tune............I am as MOPAR as anybody, but I am also a realist and I know, just because it is a Mopar, does not automatically make it the fastest, or the most powerful. As Wayne said, the HEMI was king in its day, because of shear airflow, but the design itself is not the greatest. If it was, why is it, the wedge engines rule in N/A classes.............Call the NEW HEMI whatever you want, but it is basically a "twisted wedge" chamber and is NOT hemispherical at all.

Monte
bwdst6  
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However I did pull these from a trash can when after INDY when a Barton motor came apart in an SS car. what strikes me here is the out of the box appearance and far from what I expeceted to see from one of their motors.Later I learned this was not one of their "A" combos and no likely to have the trick stuff.

I don't think there is a lot they can do, rules wise. I had bought a crank recently from Mr. Barton and I told him my bob weight so he could take care of balancing it for me. I told him I needed grams. And that surprised him!!! Surprised HIM of all people! Now I made it a point on my part, when I put my engine together to address weight, especially rotational inertia so it is a good number compared to most hemis. The point is I recall him saying that his SS engines are running weights that aren't much better than the OEM configuration so they might not be able to do much. But I don't know, I have never looked at a SS rule book.
This post is available in double vision where drunk. Mopar_Rich  
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Sonora CA Here's an excerpt from my Hemi book:

It�s interesting to note that a Hemi provides a unique set of problems because the piston to head clearance is not a flat surface so quench is hard to control. Manufacturers do their best to conform the shape of the dome to the chamber thereby creating some quench. I like calling this �squench� because it�s different from a wedge but the process is the same. Because of this when I use clay to measure the piston to valve clearance I also measure the �squench� distance too.

If the desired compression ratio is high, the stroke is low, and the valve lift is high, the resulting piston can end up with deep valve pockets and a peaked top. This limits flame travel. I try to specify that I want the top of the dome clipped slightly and I�ll live with a little less compression.

Notice too that as the bore size increases the piston is left with a flat perimeter around where the head�s chamber dome would end. This becomes a secondary quench area where you must make sure you have adequate piston to head clearance.


So the bottom line is - Hemis are tough to get a high CR while controlling all the other issues.
W.I.N. Racing  
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Byron, NY Boost also gives you compression, (more air/fuel volume same space)
Hemi's lack the ability to have the type of compression that wedge designs do, partly due to the fact that the entire valve face diameter of both valves needs to be clearanced in the piston. Meaning, as you fill the chamber with piston you must relieve the dome of more material, compound that by valve lift/rocker ratio and the pocket becomes quite large, taking away compression and having negative effects on flame travel. As far as the Landy design piston, that was available from Venolia back in the late 80's. I had a very similar design in my last iron motor but instead of removing all the material from the crown (between the valve clearance trench) I only used a notch on each side to allow some flame travel balance. Also I had the valve clearance pockets fly cut(flat), my next motor was to have the pocket area plunge cut with a tulip shape cutter to eek out a little more compression. never got there. I'll look and see if have an old piston laying around and post a pic if I do.
But the Achilles' heel of the Hemi is compression, piston weight is down the list from there.
You get compression in them and stabilize the rocker system and you will find the power.
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The disadvantage the Hemi has is NOT from quench.......it's from terrible valve angles (for a naturally aspirated application) and piston weight...........and the ONLY reason Hemi's do well in Super Stock is because they have two carbs, instead of one like the Chevy's.....

Terrible valve angles...

2 carbs

In the last few years NHRA has allowed '64 Hemi cars to run 1 carb in A/stock as long as it's a NASCAR intake. From what I'm seeing they run pretty darn good for antiques.

Your carb answer is a moot point since they never orginally made any single carb drag or street packages and can't be proven.

It's proven everyday, on race tracks everywhere. The SS/AH combo is a bad hombre, don't get me wrong, BUT, if you let a 427 Chevy weigh the same and get a sheetmetal intake, with two carbs, you might be singing another tune............I am as MOPAR as anybody, but I am also a realist and I know, just because it is a Mopar, does not automatically make it the fastest, or the most powerful. As Wayne said, the HEMI was king in its day, because of shear airflow, but the design itself is not the greatest. If it was, why is it, the wedge engines rule in N/A classes.............Call the NEW HEMI whatever you want, but it is basically a "twisted wedge" chamber and is NOT hemispherical at all.

Monte

I never mentioned that a HEMI was better and never intended to sound like I did..It's just his point(and now yours) can't be proven because it's comparing apples to oranges.

A HEMI has a number of disadvantages compared to a Chevy..rocker gear weight,piston weight/dome, combustion chamber too large and the exhaust valves on street HEMI style heads moved a few degrees to clear the shock towers.

and no one can go back in time and change what is.
mbogina  
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Kansas City Metro Big Squeeze/Monte- I respectfully disagree with your statements comparing Chevy 427 SS vs a Hemi. If both motors were run at an equal HP factor/weight and both were allowed the same intakes and carbs, the Hemi would still spank the Chevy. The only way the Chevy can run with me is because they weigh 150+ lbs less than me (Street Hemi Combo). I could trade my 2 625 carters for their 1 850 Holley, remove the weight and still outrun them. If they were allowed another 400 cfm, same compression, and same race weight, I would still outrun them. The Chevy would have to gain 30-40 HP with the 400 cfm increase in order to make up the weight penalty, not gonna happen. If you wish to compare the Race Hemi version instead, simply look at the AH cars vs the AA chevys- the Chevy motors are rated at way less HP, yet they run .2-.4 slower- do you really think that another 710 cfm (2-780 vs 1-850)would allow the Chevy to make 60-120 HP more? Depending on which version of the Chevy 427 used, they would also have to add significant weight to their combo, so they would need to make even more power. While I do agree that the large surface area of the Hemi chamber creates a longer burn time, the valve layout affords sufficient breathing to eliminate the disadvantage. Now, in the Pro Stock world of unobtanium parts, yes, a head can be designed with all the Hemi advantages and all the wedge advantages, clearly superior to the 55 year old technology that I run.
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Bend,OR USA We don't call them Hemiroids for nothin Now, if we had a double overhead cam hemi in production that could possibly resolve this debate NOT I was suprised several years ago when I built my first pump gas low compression street stroker motor that ended up making 1.37 HP per C.I. with a set of ported 906 iron heads. I was building and dyno testing a lot of motors then and I had not had a pump gas 426 Hemi make as much HP or torque per C.I. as that low deck wedge stroker did Still haven't That 512 low deck motor had absolutely no quench, 22 CC dished pistons .025 in the hole with a .042 thick head gasket and I used a stock low deck Edelbrock six pak intake and factory vacume carbs. I guess my message is anyone can make power with a wedge, not all of us can do the same with a 426 Hemiroid Maybe Ma Mopar saw the writing on the wall( 426 Hemis don't work as good as the L.A SB do HP per C.I.) ) and decided to quit making them(426 hemis) and blame it on the govement emission rules and insurance companys
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We don't call them Hemiroids for nothin Now, if we had a double overhead cam hemi in production that could possibly resolve this debate NOT I was suprised several years ago when I built my first pump gas low compression street stroker motor that ended up making 1.37 HP per C.I. with a set of ported 906 iron heads. I was building and dyno testing a lot of motors then and I had not had a pump gas 426 Hemi make as much HP or torque per C.I. as that low deck wedge stroker did Still haven't That 512 low deck motor had absolutely no quench, 22 CC dished pistons .025 in the hole with a .042 thick head gasket and I used a stock low deck Edelbrock six pak intake and factory vacume carbs. I guess my message is anyone can make power with a wedge, not all of us can do the same with a 426 Hemiroid Maybe Ma Mopar saw the writing on the wall( 426 Hemis don't work as good as the L.A SB do HP per C.I.) ) and decided to quit making them(426 hemis) and blame it on the govement emission rules and insurance companys

You saying you can't make 700hp with a 512 hemi but you can with a 906 head?






I know of one 493 hemi that makes more with stock ex manifolds and stock intake and 2 carter AFBs
I am not causing global warming, I am just trying to hold off a impending Ice Age!



Monte_Smith  
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Big Squeeze/Monte- I respectfully disagree with your statements comparing Chevy 427 SS vs a Hemi. If both motors were run at an equal HP factor/weight and both were allowed the same intakes and carbs, the Hemi would still spank the Chevy. The only way the Chevy can run with me is because they weigh 150+ lbs less than me (Street Hemi Combo). I could trade my 2 625 carters for their 1 850 Holley, remove the weight and still outrun them. If they were allowed another 400 cfm, same compression, and same race weight, I would still outrun them. The Chevy would have to gain 30-40 HP with the 400 cfm increase in order to make up the weight penalty, not gonna happen. If you wish to compare the Race Hemi version instead, simply look at the AH cars vs the AA chevys- the Chevy motors are rated at way less HP, yet they run .2-.4 slower- do you really think that another 710 cfm (2-780 vs 1-850)would allow the Chevy to make 60-120 HP more? Depending on which version of the Chevy 427 used, they would also have to add significant weight to their combo, so they would need to make even more power. While I do agree that the large surface area of the Hemi chamber creates a longer burn time, the valve layout affords sufficient breathing to eliminate the disadvantage. Now, in the Pro Stock world of unobtanium parts, yes, a head can be designed with all the Hemi advantages and all the wedge advantages, clearly superior to the 55 year old technology that I run.

I understand everything you are saying, but I was not referring to anything, based on the NHRA factored HP system. Let's do it this way. 426 HEMI, 427 Chevy, same weight car, sheetmetal intakes, two Holleys and any stock valve angle, stock port layout head they choose. Who you got???? That is as apples to apples as it comes.

Monte
torkrules  
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those hemis were a nightmare to tune due to the massive combustion chambers which slowed flame speed dramatically , the higher these engines were spun the more timing was necessary to make power , there was no 'cut off point' the engine just decided it had enough & hammered the pistons/rings out ,

I heard Gartlis tell the story of how he did not want to run the 426 the first year. the 392 had broke 200 MPH and that was his sales pitch for appearances. well after quite a few tries the 426 only went 198. In his attempt to intentionally destroy it and go back to the 392 he bumped the timing to a then unheard of 40 degrees . BAM 207 upped it to 45 hit 213mph

I think the Ramchargers figured this out before Garlits did much the same way Garlits did. There top fuel car just wasn't running as it should and I think Maxwell came up with idea of bumping the timing. I think I read they got up as high as 60 degrees and it really turned on at that point(and they at that point started to bust up things as they hadn't discovered aluminum rods yet). They weren't sharing that little piece of info with anyone else at the time.
torkrules  
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We don't call them Hemiroids for nothin Now, if we had a double overhead cam hemi in production that could possibly resolve this debate NOT I was suprised several years ago when I built my first pump gas low compression street stroker motor that ended up making 1.37 HP per C.I. with a set of ported 906 iron heads. I was building and dyno testing a lot of motors then and I had not had a pump gas 426 Hemi make as much HP or torque per C.I. as that low deck wedge stroker did Still haven't That 512 low deck motor had absolutely no quench, 22 CC dished pistons .025 in the hole with a .042 thick head gasket and I used a stock low deck Edelbrock six pak intake and factory vacume carbs. I guess my message is anyone can make power with a wedge, not all of us can do the same with a 426 Hemiroid Maybe Ma Mopar saw the writing on the wall( 426 Hemis don't work as good as the L.A SB do HP per C.I.) ) and decided to quit making them(426 hemis) and blame it on the govement emission rules and insurance companys

FWIW my first go around with one of these things did bring a few things to light. Previously I has a 496 wedge with a .650 lift 290 duration roller cam, carb and eddy heads that flowed around 310, and had 11.2 comp. that engine made 630HP/650lb.ft of torque. It was all done at and made max torque at rpm.

The Hemi is a 472, K8 Hyd cam, MP single 4 intake, 9.5 comp, and intakes that flowed around 320 (this was the first go around). It made Hp at /585lb ft of torque at . It seemed to me it was a lot easier to get the performance out of the Hemi without going too radical and it did it's best at 33 degrees timing as opposed to 35 for the wedge.

I have found that it's not totally immune to pingging. There are other factors here that make this combo different (heavier car, less gear, 4 speed) but you still need to keep this in mind.
jim sciortino  
top fuel

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Trumbull,CT. Funny how people overlook the flaws on the Chevy head and the millions spent on R&D to correct them over the last 4+ decades.

Do max effort "chevy" heads retain their sloppy chambers, or weak rockertrain, or lousy ports (among other things)...........I think not. If it comes down to FACTORY iron, I'll take a HEMI over a 427.

We all see how the development of the "99" prostock head does in the power making department. Is it radically different than a stock HEMI??? Of course......but so are the chevy heads compared to a stock iron rec. port head.

ALL factory performance heads had strong points and drawbacks, it's the aftermarket that has been kind to the chevy and ford deals for economic reasons that has led to their capabilities. As was mentioned in a pervious post, lets go back in time to parts and see how the chevys and fords would do without their non-stop, aftermarket development against the HEMI.

If I recall, they did't fare to well before the heavy hands of NASCAR and the NHRA put the HEMI to bed.
B G Racing  
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Eighty Four, PA Not looking to get into a big debate but the hemi design was the greatest thing that happened to engine cylinder head development in centurys.That the demise of the hemi came at the hands of NHRA and NASCAR and no further development followed made the hemi design obsolete other than the feeble attempts of Ford and GM's alternate designs.With the advent of foriegn auto manufactures using the design in some semblance of the original configuration making some of their engine very efficient hopefully some sort of R&D will get the interest stimulated again.The biggest drawback(in my opinion) is the rocker and pushrod design and always felt that the attempts to eliminate the issues(like Ford) with the daul overhead cams that if R&D would have advanced the Hemi would reign supreme in racing venues today.The strides of manufactures to improve wedge and canted valve style heads has give them a slight edge over the obsolete under developed hemi heads as we know it.With the cost of such development and todays economy,I don't see anyone willing to spend the money for improving the hemi design for only a limited market.
Last edited by B G Racing; 01:40 PM. sshemi  
top fuel

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sweden

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I need to fill in with what i always say to my friends complaining about the old american iron motors.... you dont see any chevys/japs run in top fuel.

What works for a blown fuel combo, has absolutely ZERO bearing, on what translates to real world motors. Blown motors, are terribly inefficient, heavy pack mules. There is nothing trick about them, nor will ANY single part of it, transfer to a stock HEMI. They have two things going for them, they are extremely durable and required by the rules. A blown motor is simple, massive ports, massive fuel and push as much of each through it as you can. All of that has no bearing on a N/A motor.

Monte

whooh... that was just a joke.
I dont think you need to be super smart to understand that Chryslers 426 hemi motor design is NOT the best out there.
If it was every motor in performance cars would have a similar design.
And i agree a sb makes much more tq/cui than a hemi.
torkrules  
I'm neurotic

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closer to Canadian beer!

Quote:
Not looking to get into a big debate but the hemi design was the greatest thing that happened to engine cylinder head development in centurys.That the demise of the hemi came at the hands of NHRA and NASCAR and no further development followed made the hemi design obsolete other than the feeble attempts of Ford and GM's alternate designs.With the advent of foriegn auto manufactures using the design in some semblance of the original configuration making some of their engine very efficient hopefully some sort of R&D will get the interest stimulated again.The biggest drawback(in my opinion) is the rocker and pushrod design and always felt that the attempts to eliminate the issues(like Ford) with the daul overhead cams that if R&D would have advanced the Hemi would reign supreme in racing venues today.The strides of manufactures to improve wedge and canted valve style heads has give them a slight edge over the obsolete under developed hemi heads as we know it.With the cost of such development and todays economy,I don't see anyone willing to spend the money for improving the hemi design for only a limited market.

I remember reading something that Tom Hoover said years ago. The mentality wasn't to improve things it was to maximize profits. If you needed more power you made it bigger. You can see some mind set change in the 3G Hemi. Still not there yet, but you can see the improvement being made in the right direction. Had the 2G survived, who knows where it might be if they had spend the time and dollars to improve the initial design.

In my opinion it was always a compromise (they were sticking Hemi heads on a wedge block after all for expediency). What would have been produced had the whole thing been done from scratch? Who knows.
52savoy  
master

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Quote:
Funny how people overlook the flaws on the Chevy head and the millions spent on R&D to correct them over the last 4+ decades.

Do max effort "chevy" heads retain their sloppy chambers, or weak rockertrain, or lousy ports (among other things)...........I think not. If it comes down to FACTORY iron, I'll take a HEMI over a 427.

We all see how the development of the "99" prostock head does in the power making department. Is it radically different than a stock HEMI??? Of course......but so are the chevy heads compared to a stock iron rec. port head.

ALL factory performance heads had strong points and drawbacks, it's the aftermarket that has been kind to the chevy and ford deals for economic reasons that has led to their capabilities. As was mentioned in a pervious post, lets go back in time to parts and see how the chevys and fords would do without their non-stop, aftermarket development against the HEMI.

If I recall, they did't fare to well before the heavy hands of NASCAR and the NHRA put the HEMI to bed.

another correct answer....

No one has mentioned that Chevy designed the "mystery motor" over several years and still it had a hard time outrunning a Hemi(10 years of NASCAR and NHRA sanctions made it possible). The Hemi was on the drawing board and won Daytona in less than a year(11 months?) from what I remember...
using a (modified)passenger car blocks and old 392 Hemi head technology. Not bad for a motor that was thrown together...
and now (almost)50 years later copies of them are making 7,000+ horsepower or 14 hp pci...how can that be considered inefficient

http://en.wikipedia.org/wiki/Chevrolet_Big-Block_engine