Re: HEMI Quench?
[Re: 52savoy]
#815917
09/28/10 02:02 PM
09/28/10 02:02 PM
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Joined: Nov 2004
Posts: 6,890 North Alabama
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 1964 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
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Re: HEMI Quench?
[Re: Big Squeeze]
#815920
09/28/10 02:19 PM
09/28/10 02:19 PM
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Joined: Dec 2006
Posts: 2,137 Byron, NY
W.I.N. Racing
top fuel
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top fuel
Joined: Dec 2006
Posts: 2,137
Byron, NY
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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.
'01 P1500, Blown/Inj BAE,/Veney ,Bruno/CS2,Dana 60 '01 Dodge 3500 S Cummins Auto, Fresh air kit, 4" Exhaust, '05 Dodge Magnum R/T - Too Much to list '60 Willys CJ5 '01 International LPX - Project,DT466, Allison '64 Plymouth Valiant, Inj 528 Hemi, 2spd
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Re: HEMI Quench?
[Re: Monte_Smith]
#815921
09/28/10 02:35 PM
09/28/10 02:35 PM
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Joined: Dec 2005
Posts: 4,299 State of Fascism
52savoy
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State of Fascism
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Quote:
Quote:
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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 1964 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.
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Re: HEMI Quench?
[Re: 52savoy]
#815922
09/28/10 03:09 PM
09/28/10 03:09 PM
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Joined: Dec 2005
Posts: 293 Kansas City Metro
mbogina
enthusiast
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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.
Be a Rebel- Break the Laws of Physics!
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Re: HEMI Quench?
[Re: 52savoy]
#815923
09/28/10 03:21 PM
09/28/10 03:21 PM
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Joined: Dec 2008
Posts: 1,200 UK
602heavy
pro stock
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pro stock
Joined: Dec 2008
Posts: 1,200
UK
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You see guys drooling over hemis as if they are the be all & end all , yea they look great sitting in the engine bay , or the typical "wow you got a hemi" type guys , although the wedge head is not the most efficiant of head design i'd take it over a hemi any day of the week. As posted in another thread , 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 , there is a good article written by a guy called Cline , wish i could find it as i'd post it up.
Last edited by 602heavy; 09/28/10 03:25 PM.
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Re: HEMI Quench?
[Re: 602heavy]
#815924
09/28/10 03:31 PM
09/28/10 03:31 PM
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Joined: Dec 2005
Posts: 293 Kansas City Metro
mbogina
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Kansas City Metro
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the Hemi is not a nightmare to tune and does not require high timing. My SS motor runs at 28 degrees timing in good weather, as much as 33 degrees in bad. I recently dyno'ed a 572 Mopar wedge with reverse dome pistons, pump gas and 440-1 heads that required 42 degrees timing for max power.
Be a Rebel- Break the Laws of Physics!
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Re: HEMI Quench?
[Re: mbogina]
#815925
09/28/10 03:59 PM
09/28/10 03:59 PM
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Joined: Dec 2008
Posts: 1,200 UK
602heavy
pro stock
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pro stock
Joined: Dec 2008
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Quote:
I recently dyno'ed a 572 Mopar wedge with reverse dome pistons, pump gas and 440-1 heads that required 42 degrees timing for max power.
Depends what the intended application was , if built for NA set up then i would say that engine is pretty inefficiant with 42* spark lead.
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Re: HEMI Quench?
[Re: 602heavy]
#815926
09/28/10 04:18 PM
09/28/10 04:18 PM
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Joined: Aug 2004
Posts: 2,128 sweden
sshemi
top fuel
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top fuel
Joined: Aug 2004
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sweden
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have anyone ever had to use more than 38*timing on a Hemi? A bigger area combution chamber will make more force to/at the piston. And a hemi chamber has some big area. 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.
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Re: HEMI Quench?
[Re: sshemi]
#815927
09/28/10 04:27 PM
09/28/10 04:27 PM
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Joined: Dec 2005
Posts: 293 Kansas City Metro
mbogina
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Kansas City Metro
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602Heavy- I don't really believe the 572 in question was very inefficient- 840 HP, 757 TQ, 10.9 Comp, .38-.40 BSFC on 91 octane pump gas street motor, gets driven 3000+ miles a year.
Be a Rebel- Break the Laws of Physics!
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Re: HEMI Quench?
[Re: mbogina]
#815931
09/28/10 05:31 PM
09/28/10 05:31 PM
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Joined: Dec 2008
Posts: 1,200 UK
602heavy
pro stock
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pro stock
Joined: Dec 2008
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UK
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Quote:
602Heavy- I don't really believe the 572 in question was very inefficient- 840 HP, 757 TQ, 10.9 Comp, .38-.40 BSFC on 91 octane pump gas street motor, gets driven 3000+ miles a year.
Nice #s. ......i'm only pointing out the fact the engine 'could' be more efficient , the earlier the spark is fired off the more pressure is put upon the piston as it moves toward TDC , 42* is a lot of advance when running 91 octane , not being critical of you're build just throwing out opinions , which don't add up to much anyhow.
I had a 9.5:1 605" wedge that ran 44* spark lead , milled the heads etc & raised CR to 10.4:1 , the engine ran best around 34* advance on 97 octane....faster the burn the more efficient the engine will be.
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Re: HEMI Quench?
[Re: mbogina]
#815932
09/28/10 06:50 PM
09/28/10 06:50 PM
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Joined: Nov 2004
Posts: 6,890 North Alabama
Monte_Smith
master
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master
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Posts: 6,890
North Alabama
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Quote:
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
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Re: HEMI Quench?
[Re: sshemi]
#815933
09/28/10 06:59 PM
09/28/10 06:59 PM
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Joined: Nov 2004
Posts: 6,890 North Alabama
Monte_Smith
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Quote:
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
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Re: HEMI Quench?
[Re: Monte_Smith]
#815934
09/28/10 08:26 PM
09/28/10 08:26 PM
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Joined: Jan 2005
Posts: 12,478 Kalispell Mt.
HotRodDave
I Live Here
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Kalispell Mt.
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Flame travel is not as bad as it would apear simply looking at the piston because the flame starts in the very center directly above the piston, not on the very edge of the chamber like a 906 head, a big dome in the 906 head will block the far side of the chamber from a good flame front, not so much in a hemi though.
I am not causing global warming, I am just trying to hold off a impending Ice Age!
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Re: HEMI Quench?
[Re: HEMIFRED]
#815935
09/28/10 10:03 PM
09/28/10 10:03 PM
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Joined: Nov 2003
Posts: 2,715 closer to Canadian beer!
torkrules
I'm neurotic
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I'm neurotic
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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.
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