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Re: In your opinion, who has the best combustion chamber?
[Re: EchoSixMike]
#1598101
03/26/14 10:19 AM
03/26/14 10:19 AM
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Joined: Feb 2005
Posts: 20,169
PA.
pittsburghracer
"Little"John
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"Little"John
Joined: Feb 2005
Posts: 20,169
PA.
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Quote:
The OP said big block and eliminated all the serious race stuff. He also just asked about combustion chambers, which is sort of odd, when there's other things much more pertinent to making power. The BS comes in about 65cc and when CNC'd about 75, which is about where you want to be with a flat top piston.
AFAIK, none of the common Mopar heads come with semi finished chambers so they can be properly CNC machined, as is SOP with serious stuff, but the BS is probably best suited to this, for the reasons I mentioned.
Would that be what I recommend? No, I have a set of Victors for the engine that's going to the step down from the B-1. That would be my suggestion at present. S/F....Ken M
The B1BS can be a VERY good head when ported. A local PRP racer has gone some nice 8.60's with his in his 69 Charger NA.
1970 Duster
Edelbrock headed 408
5.984@112.52
422 Indy headed small block
5.982@112.56 mph
9.42@138.27
Livin and lovin life one day at a time
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Re: In your opinion, who has the best combustion chamber?
[Re: 74yellowduster]
#1598102
03/26/14 11:00 AM
03/26/14 11:00 AM
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Joined: May 2003
Posts: 6,561
Downtown Roebuck Ont
Twostick
Still wishing...
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Still wishing...
Joined: May 2003
Posts: 6,561
Downtown Roebuck Ont
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Quote:
"modern" combustion chamber "design"
hmmmm
turbos are modern. oh wait they were designed in 1905. over 100 years ago lol.
get off the modern thing and think instead.
the shape of a combustion chamber is only going to change things minutely. what really matters is flow, velocity, compression ratio, etc. quench/squish/all that crap comes into play if you are not using race gas. if it's a street engine then you are limited by fuel.
if you have lots of E85 available local to you then you can go 12.5:1 compression.
that being said, the heads with raised ports will outperform the stock sized port heads every time.
so W9's and Victors and some others with raised ports will eat up the other ones, especially at higher rpms. combustion chamber design has little to do with this. but if you are on the street you are not going to be runnin around at 7200 rpms and stuff.
You and the gentleman above you are misinformed/mistaken if you think combustion chamber shape is of little concern.
Look no further than a Gen 3 Hemi. They make big block power, get slant 6 fuel economy and the max timing advance is in the low 20's. They can do this because the combustion chamber shape gives it the ability to actually burn ALL the fuel in the chamber BEFORE it gets to BDC.
Another example would be a new LS7 GM. 11:1 CR from the showroom. You haven't been able to do that with a 915 chamber since the sixties.
Hot Rod did an article when the Vortec head first came out and on a mild 355 SBC with the usual bolt ons, a set of parts counter Vortec's were good for 70 HP with less than 30 deg timing.
And yes the new engines have all kinds of electronic management but you can pile computers up 3 deep on an RPM headed Mopar and it won't run at 11:1 on pump gas and make power without a huge cam to vent cylinder pressure out the exhaust at lower engine speed.
The difference in flame travel speed is minute maybe a millisecond +/- but in terms of efficiency it is FOREVER. To use the Gen 3 analogy, same/more power as a BB at 10-15 deg LESS timing and a lot less cubes. The less timing part is the clue as to what is happening and when it is happening.
Kevin
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Re: In your opinion, who has the best combustion chamber?
[Re: Twostick]
#1598104
03/26/14 04:10 PM
03/26/14 04:10 PM
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Joined: Jan 2013
Posts: 167
maryland
74yellowduster
member
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member
Joined: Jan 2013
Posts: 167
maryland
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Quote:
run at 11:1 on pump gas and make power without a huge cam to vent cylinder pressure out the exhaust at lower engine speed.
inform this
"variable cam timing" in the gen3
I wonder what that does?
and the LS7 "Variable valve timing (VVT) is a standard feature on 6.0L and 6.2L engines"
it's pretty much standard on 11:1 pump gas engines
it has nothing to do with production of power, it's rather for the prevention of knock.
the thread starter will probably not find a variable timing camshaft for his BB mopar. that being said he should probably go with raised ports if he wants all out power. combustion chamber design and flame travel has very little to do with power. they are to prevent knock/detonation.
Quote:
A technique used to prevent the onset of knock is the high "swirl" engine that forces the intake charge to adopt a very fast circular rotation in the cylinder during compression that provides quicker and more complete combustion. It is possible to manufacture gasoline engines with compression ratios of over 11:1 that can use 87 (MON + RON)/2 (octane rating) fuel with the addition of variable valve timing and knock sensors to delay ignition timing. Such engines may not produce their full rated power using 87 octane gasoline under all circumstances, due to the delayed ignition timing. Direct fuel injection, which can inject fuel only at the time of fuel ignition (similar to a diesel engine), is another recent development which also allows for higher compression ratios on gasoline engines.
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Re: In your opinion, who has the best combustion chamber?
[Re: 74yellowduster]
#1598105
03/26/14 05:44 PM
03/26/14 05:44 PM
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Joined: May 2003
Posts: 6,561
Downtown Roebuck Ont
Twostick
Still wishing...
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Still wishing...
Joined: May 2003
Posts: 6,561
Downtown Roebuck Ont
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Quote:
Quote:
run at 11:1 on pump gas and make power without a huge cam to vent cylinder pressure out the exhaust at lower engine speed.
inform this
"variable cam timing" in the gen3
I wonder what that does?
and the LS7 "Variable valve timing (VVT) is a standard feature on 6.0L and 6.2L engines"
it's pretty much standard on 11:1 pump gas engines
it has nothing to do with production of power, it's rather for the prevention of knock.
the thread starter will probably not find a variable timing camshaft for his BB mopar. that being said he should probably go with raised ports if he wants all out power. combustion chamber design and flame travel has very little to do with power. they are to prevent knock/detonation.
Quote:
A technique used to prevent the onset of knock is the high "swirl" engine that forces the intake charge to adopt a very fast circular rotation in the cylinder during compression that provides quicker and more complete combustion. It is possible to manufacture gasoline engines with compression ratios of over 11:1 that can use 87 (MON + RON)/2 (octane rating) fuel with the addition of variable valve timing and knock sensors to delay ignition timing. Such engines may not produce their full rated power using 87 octane gasoline under all circumstances, due to the delayed ignition timing. Direct fuel injection, which can inject fuel only at the time of fuel ignition (similar to a diesel engine), is another recent development which also allows for higher compression ratios on gasoline engines.
Let's see now..
Gen 3 Hemi no VVT until '09. 6.1 425 HP 10.3:1
The LS7 'Vette engine might have VVT now but it didn't in '06. 11:1 505 HP.
There is no way on any planet you could make those numbers at that displacement with a 915 style chamber with a cam that will idle dead smooth at 700 rpm without race gas.
Quote:
combustion chamber design and flame travel has very little to do with power. they are to prevent knock/detonation.
Kind of makes my point. If it knocks, it won't make power. If it don't knock... The fast burn chamber makes more power specifically because it prevents detonation and requires less timing. The less timing and faster flame travel is where all the "free" power is hiding.
Kevin
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Re: In your opinion, who has the best combustion chamber?
[Re: jim sciortino]
#1598106
03/27/14 12:29 AM
03/27/14 12:29 AM
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Joined: Jan 2003
Posts: 15,439
Val-haul-ass... eventually
BradH
Taking time off to work on my car
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Taking time off to work on my car
Joined: Jan 2003
Posts: 15,439
Val-haul-ass... eventually
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Quote:
All current out of the box chambers offered for the wedge MOPAR, except the Predator and custom PSO stuff are outdated and inefficient.
All the Joe Average BBM heads are about 20 years (or more) old in basic design now, while the rest of the world has moved on at least a generation ahead in valve placement, angles, pressure recovery, etc.
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