hemi advantage?
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66plyValiant
Well-Known Member
the old hemi's (426) were always a good choice in stock form over every other engine
the older 392 and 331 hemi's are more of a cool factor, they can be high HP too mind you with all the modern parts they make, but they are also very costly to build
the older 392 and 331 hemi's are more of a cool factor, they can be high HP too mind you with all the modern parts they make, but they are also very costly to build
805moparkid
Slant and AFX Guy
All new motors except for the LS are a hemi... All your 4 valve motors are pent-roof Hemi's
inkjunkie
Well-Known Member
Just from a flow stand point....Tim at FHO can get 547 intake/340 exhaust out of a Stage 5 Millennium head...Think the Predator heads are in the same area on a big enough bore....but at a very high $$ amount. Last I looked a set of them, with a tunnel ram was near 12k....
I'm not talking extreme here. I'm asking if the hemi head actually has a performance advantage now with the average aftermarket aluminum wedge head. As in take a stock street hemi, build a wedge to same specs only with rpm/440 source/indy heads, does the hemi have the advantage still?
805moparkid
Slant and AFX Guy
a street hemi is a POS, a 440 mag would eat them up like nothing. The real question is your scenario and a race hemi...
66plyValiant
Well-Known Member
"The street Hemi version was rated at 425 bhp (316.9 kW)(Gross) with two Carter AFB carburetors. In actual dynomometer testing, it produced 433.5 horsepower and 472 lb·ft (640 N·m) torque in purely stock form.[5] Interestingly, Chrysler's sales literature[6] published both the gross 425 hp (317 kW; 431 PS) and net 350 hp (261 kW; 355 PS) ratings for 1971."
350 HP is a POS? those are big numbers for 1971, comparable to what 500 HP would be these days to people (a big deal)
67Dart273
Well-Known Member
Having owned a V code car I can tell you this just is not true. I knew a LOT of guys with 440s and a few hemis back then. A V code might stay with or beat hemi now and then, but it would not "eat it up" and a Magnum ----which was a 4bbl, had no chance. None.
moparlover
Well-Known Member
hemis were designed as race engines, with a street version created to keep it legal for racing.
top fuel cars still after 40 years use a version of the same engine. I believe the common one is 7:1 compression with special venolia anodized pistons, 496 cubic inch, a huge blower and runs on 90% nitromethane. their estimated horsepower is in the area of 8000hp
the bore they use is slightly smaller than the original 426 hemi but they use a 4.500 stroke
you wont see them switching to a new gen hemi anytime soon, or turbo, or wedge or chevy
just to put it in perspective, those cars the fuel pumps can pump 93 gallons per minute
most of us get HP fuel pumps that pump around 120 or 150 gallons per hour
top fuel cars still after 40 years use a version of the same engine. I believe the common one is 7:1 compression with special venolia anodized pistons, 496 cubic inch, a huge blower and runs on 90% nitromethane. their estimated horsepower is in the area of 8000hp
the bore they use is slightly smaller than the original 426 hemi but they use a 4.500 stroke
you wont see them switching to a new gen hemi anytime soon, or turbo, or wedge or chevy
just to put it in perspective, those cars the fuel pumps can pump 93 gallons per minute
most of us get HP fuel pumps that pump around 120 or 150 gallons per hour
805moparkid
Slant and AFX Guy
not relating to these days, im relating to what it really is and what was posted, The Race Hemi...
MopaR&D
Nerd Member
The Hemi chamber by design has more of an advantage in flow in the mid-to-upper RPM range and it is actually not very hard to achieve 100% volumetric efficiency from a lightly modified 2nd-gen Chrysler Hemi. You can build a wedge that will make the same peak HP/TQ numbers but they will more often than not be at a lower speed than the Hemi and will trail off quick after peak. The Hemi kind of just keeps making torque the higher you spin it, hell the factory redline was 6500 RPM and they were made to be able to rev past 7000.
Moneywise it's still almost always cheaper to build a hot wedge than a Hemi but to answer your question yes, the old Hemi heads still have advantages over the new aftermarket wedge heads. HOWEVER they also have disadvantages, main one being pretty bad combustion efficiency at lower speeds esp. with those giant domed pistons obstructing the flame travel across the chamber and the lack of any squish areas on the old-style chambers. If you look at the new (3rd-gen) Hemi chamber it has squish pads added on the sides of the valves as well as two plugs per cylinder all to help speed up combustion at lower speeds and help fuel economy and emissions.
Moneywise it's still almost always cheaper to build a hot wedge than a Hemi but to answer your question yes, the old Hemi heads still have advantages over the new aftermarket wedge heads. HOWEVER they also have disadvantages, main one being pretty bad combustion efficiency at lower speeds esp. with those giant domed pistons obstructing the flame travel across the chamber and the lack of any squish areas on the old-style chambers. If you look at the new (3rd-gen) Hemi chamber it has squish pads added on the sides of the valves as well as two plugs per cylinder all to help speed up combustion at lower speeds and help fuel economy and emissions.
Hersbird
Well-Known Member
The newer motor is an improvement on the old, just like the 426 was an improvement on the original Hemi. I'd take a modern SRT 6.4 in my muscle car over a 65-71 426 anyway.
If you do some good research, you will find that the only "true" Chrysler Hemi was the first generation Dodge, Desoto and Chrysler engines beginning in 1951. Even the 2nd generation 426 heads are not considered as much of a Hemi design as the original. It is even arguable that the new Hemi is even a Hemi at all. There are lots of articles and information about it. Just because plug wires go through the valve cover does not make an engine a Hemi. It has to do with the combustion chamber shape, valve arrangement and spark plug position.
But yes, ALL the engines Chrysler gave the Hemi name have several advantages, regardless or the "Hemi or not" argument. The biggest being the shape of the combustion chamber and the fact that the chambers are all finish machined. Unlike conventional wedge chambers that are "as cast" and have tiny bumps that do not allow even heat distribution, the finish machined Hemi chambers are very smooth, promoting an even burn and lower combustion temperatures, allowing efficiency to go up. They can even run on a lesser octane fuel for the same given compression ratio as compared to a conventional wedge design like a big or small block.
Also, with the intake and exhaust valves right across from each other, the air and fuel mixture has a very straight, unobstructed path into and out of the cylinder. All of these things add up to a much more efficient cylinder head and a more overall efficient engine.
But yes, ALL the engines Chrysler gave the Hemi name have several advantages, regardless or the "Hemi or not" argument. The biggest being the shape of the combustion chamber and the fact that the chambers are all finish machined. Unlike conventional wedge chambers that are "as cast" and have tiny bumps that do not allow even heat distribution, the finish machined Hemi chambers are very smooth, promoting an even burn and lower combustion temperatures, allowing efficiency to go up. They can even run on a lesser octane fuel for the same given compression ratio as compared to a conventional wedge design like a big or small block.
Also, with the intake and exhaust valves right across from each other, the air and fuel mixture has a very straight, unobstructed path into and out of the cylinder. All of these things add up to a much more efficient cylinder head and a more overall efficient engine.
No, not in the design of the combustion chamber. It is actually a step backward. The only "improvement" is all of the electronics and computer control. The new Hemi head is really not a Hemi at all. They simply used the name.
Top is the 5.7 "Hemi" and bottom is the 1st generation Chrysler Hemi. The new hemi is almost a dual quench design. It is not a full hemi chamber by a long shot.
Here is a wide shot of the 426 (top) and 392 (bottom) heads. Not the spark plug position is exactly opposite from each other. I don't know all of the specifics, but something about the early Hemi design makes it more a more efficient design where they located the plug.
famous bob
mopar misfit
:wack:
after having two- 426 hemi`s, racing one for 14 years, I can truthfully say some of the above is b.s. And, if one knew how to keep a street hemi tuned, there was no stock 440 ever built that would out horse power it. might out run it because of severe traction problems on the hemi`s part. I never had anyones bigblock out run my hemi on the street. do the same cam-same c.r.-same carburation-same weight car, all 426-or 427-or 428, w/ the same size tires-s.s. leaf springs on the hemi, slapper bars on the others, runnem for a quarter, the hemi did it every time. closest to catching it was a 428 mustang on the top end, but it wasn`t totally stock. been there -done that. the currant good head flow from the aftermarket ported wedge alum. heads, "mine included" is about 350 on the intake., a bone stock street hemi had that beat by a little.----------just my 2 cents, all from experiance--------bob
Where did anybody say a 440 would outrun a Hemi? I guess I missed that.
Nevermind. I went back and saw it. It was unclear who you were responding to. I agree with you. People that say the 440 could outrun the Hemi have read too many magazines.
Nevermind. I went back and saw it. It was unclear who you were responding to. I agree with you. People that say the 440 could outrun the Hemi have read too many magazines.
You're delusional. A six pack *may have* occasionally gotten the best of a street hemi, but a 440 Magnum was no competition. The Hemi was king and everybody whose been around knows it.
moper
Well-Known Member
You mean modern aftermarket heads for the Baby, the Elephant, or the "I-wish-I-was-a-Hemi" modern 5.7/6.1/6.4L?
The best advantage would be 4 valves per cylinder like the imports and a mild dished piston with a quench ring on the perimeter. There is too much dead space and area for thermal transfer on the older Hemi stuff. They still make good power - but it's an old (like 1920s) design that ignores a lot.
Ever heard of the Covalt Hemi? that's one I would love to have.
You're right. It is an old design from aircraft engines, but it's a damn good one that's still tough to beat today, IMO. Were they still using the exact same early Hemi combustion chamber coupled with all the fancy computer stuff, I think you'd really see something. Course, I been wrong before, I could be again.
MopaR&D
Nerd Member
I have to disagree RRR in where the newer "wannabe" Hemi heads are inferior... From a pure efficiency standpoint the newer chambers don't lose anything by having those two squish pads there is still a lot of space around the valves. The included valve angle is much shallower on the newer heads because 1) it allows good compression with flat-top pistons due to smaller chamber and 2) you don't give up much to that massive 53* angle anyway. If you read about the A-279 "Ball-stud Hemi" Chrysler engineers knew this but when they designed the 2nd-gen 426 heads they were crunched for time (as we all know) and simply adapted the old 392 heads, enlarged the valves, and tilted them towards the intake side.
IMO the purist Hemi argument is dumb you can't argue with decades' worth of R&D... maybe it's just cause I'm an engineer but I would never say the older Hemis are better just because they are closer to a "true" Hemi design in fact I think they are worse as a true Hemi head isn't all that efficient anyway. Like moper said the 4-valve pentroof design is "where it's at" and is why you see it on most modern engines...
IMO the purist Hemi argument is dumb you can't argue with decades' worth of R&D... maybe it's just cause I'm an engineer but I would never say the older Hemis are better just because they are closer to a "true" Hemi design in fact I think they are worse as a true Hemi head isn't all that efficient anyway. Like moper said the 4-valve pentroof design is "where it's at" and is why you see it on most modern engines...
Hersbird
Well-Known Member
The 426 heads are not hemispheric neither were the 50s. The definition of a hemisphere is exactly 1/2 of a whole sphere. All of these are more like a 1/4 0f a sphere. Ironic to actually drop the sphere part and just use hemi which means 1/2. The quench areas of the modern heads is an improvement as pointed out already.
The old Hemi engines are better than the new ones. They had true "hemispherical" shaped combustion chambers. You could practically put a tennis ball in the head and run a flat blade across the head face and cut the ball in half.
The "new" Hemis are not true Hemis with round/spherical combustion chambers. They are more of a penta dome design. Better than a wedge, but not as good as a true Hemi.
The round/spherical combustion chamber allows for larger valves than the flat "wedge" design. Then angle the valves so the flow goes past the valve instead of around it, and you have better flow. In the wedge design, the mixture has to go around the valve. The geometry of the hemi allow for straighter ports and not having to go around the valve, but pass by it. It's simple fluid dynamics that any turns/bends in a port restrict flow. Maximum flow is in a straight line with no bends. The straighter you can keep your ports, the better they will flow.
Don Garlits once gave a speech at Mopar Nats on how he was trying to break 220 MPH. Chrysler had replaced the old 50's Hemis with the 413. He said that the big block could not make the power of the old Hemis. One track owner invited him to come race one weekend and offered him some money (like $1000) to race that weekend. He was running the 413 in the drag car, but couldn't get it near 220... 214, 216, ... No 220.
At the end of the day, he went to the control tower to get his earnings, and the owner was sitting behind his desk, with a gun on his desk, and an envelope and accused Don of "saving his motor for the Nats next weekend" and told him that he is only getting half of the money that they agreed on. Don states that you can't argue with a gun, so he took what was in the envelope and left.
The next weekend for the "Nats", he decided, "What the hell, lets put the old 392 Hemi back in the drag car."
So they put the Hemi in the car and took it to the track that next weekend. For kicks, he said that they decided to set the timing advance a little more and increase the boost on the blower trying to blow it up. Well, it didn't blow up. So they kept kicking up the advance and boost, and it wouldn't blow up, and he ended up breaking 220 MPH that weekend trying to blow up the Hemi. Don stated that the other track owner probably thought for sure that Don was "saving his motor for the Nats" after that, when he just couldn't get the big block to run as good as the old Hemi.
The "new" Hemis are not true Hemis with round/spherical combustion chambers. They are more of a penta dome design. Better than a wedge, but not as good as a true Hemi.
The round/spherical combustion chamber allows for larger valves than the flat "wedge" design. Then angle the valves so the flow goes past the valve instead of around it, and you have better flow. In the wedge design, the mixture has to go around the valve. The geometry of the hemi allow for straighter ports and not having to go around the valve, but pass by it. It's simple fluid dynamics that any turns/bends in a port restrict flow. Maximum flow is in a straight line with no bends. The straighter you can keep your ports, the better they will flow.
Don Garlits once gave a speech at Mopar Nats on how he was trying to break 220 MPH. Chrysler had replaced the old 50's Hemis with the 413. He said that the big block could not make the power of the old Hemis. One track owner invited him to come race one weekend and offered him some money (like $1000) to race that weekend. He was running the 413 in the drag car, but couldn't get it near 220... 214, 216, ... No 220.
At the end of the day, he went to the control tower to get his earnings, and the owner was sitting behind his desk, with a gun on his desk, and an envelope and accused Don of "saving his motor for the Nats next weekend" and told him that he is only getting half of the money that they agreed on. Don states that you can't argue with a gun, so he took what was in the envelope and left.
The next weekend for the "Nats", he decided, "What the hell, lets put the old 392 Hemi back in the drag car."
So they put the Hemi in the car and took it to the track that next weekend. For kicks, he said that they decided to set the timing advance a little more and increase the boost on the blower trying to blow it up. Well, it didn't blow up. So they kept kicking up the advance and boost, and it wouldn't blow up, and he ended up breaking 220 MPH that weekend trying to blow up the Hemi. Don stated that the other track owner probably thought for sure that Don was "saving his motor for the Nats" after that, when he just couldn't get the big block to run as good as the old Hemi.
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