Re: Big Ports, Big Flow #s, And Low Duration Camshafts
[Re: Street Monkies]
#1727900
01/12/15 02:20 PM
01/12/15 02:20 PM
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Joined: Jun 2003
Posts: 52,972 Romeo MI
MR_P_BODY
Master
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Master
Joined: Jun 2003
Posts: 52,972
Romeo MI
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Quote:
Like it says Is big flow #s and even bigger ports the way to go. Along with a low duration but the right lift for combo.
Just as long as you have enough lift to fill the cyls.. normally when you have big ports and big flow it wants high rpm to be efficient.. duration also tells you about the rpm.. so if your short on duration those heads might never be efficient ..... JMO
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Re: Big Ports, Big Flow #s, And Low Duration Camshafts
[Re: Street Monkies]
#1727901
01/12/15 03:03 PM
01/12/15 03:03 PM
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Joined: Jan 2005
Posts: 12,423 Kalispell Mt.
HotRodDave
I Live Here
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I Live Here
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Posts: 12,423
Kalispell Mt.
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Look at the cams in the new hemis, high flow, bigish ports and very tiny duration cams give huge HP numbers. You get the best of everything low RPM power and high RPM power without the stupid long duration cams of the 70s. They do get some decent lift but not at the expense of added duration. An average performance cam duration numbers like a comp 280 magnum 230@.050 would be downright wicked in a 6.1 hydraulic roller. Another thing to look at and glean information is the engine masters engines and cams, relatively short duration and very high lift with big flow numbers, that seems to be the biggest most consistant part of the recipe the winners use. The winning engines are making incredible TQ per cube and still making very nice HP up stairs.
I am not causing global warming, I am just trying to hold off a impending Ice Age!
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Re: Big Ports, Big Flow #s, And Low Duration Camshafts
[Re: HotRodDave]
#1727902
01/12/15 03:07 PM
01/12/15 03:07 PM
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Joined: Jun 2003
Posts: 52,972 Romeo MI
MR_P_BODY
Master
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Master
Joined: Jun 2003
Posts: 52,972
Romeo MI
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Quote:
Look at the cams in the new hemis, high flow, bigish ports and very tiny duration cams give huge HP numbers. You get the best of everything low RPM power and high RPM power without the stupid long duration cams of the 70s. They do get some decent lift but not at the expense of added duration. An average performance cam duration numbers like a comp 280 magnum [Email]230@.050[/Email] would be downright wicked in a 6.1 hydraulic roller.
Another thing to look at and glean information is the engine masters engines and cams, relatively short duration and very high lift with big flow numbers, that seems to be the biggest most consistant part of the recipe the winners use. The winning engines are making incredible TQ per cube and still making very nice HP up stairs.
Engine Masters are set up for torque.. thats where the points for winning are... I also assumed he is playing with old wedge stuff... try using modern rules on that and see what you get
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Re: Big Ports, Big Flow #s, And Low Duration Camshafts
[Re: Street Monkies]
#1727904
01/12/15 03:45 PM
01/12/15 03:45 PM
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Joined: Jun 2003
Posts: 52,972 Romeo MI
MR_P_BODY
Master
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Master
Joined: Jun 2003
Posts: 52,972
Romeo MI
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Quote:
Right Wedge it is. But I do look at a lot of the engine masters builds and I notice basically what we are all talking about. Low duration 230-250 @ .050 and 600-900 lift. Also they seem to run the biggest intake valve they can fit. In some of the heads the street class they must of moved guides to get a big valve like a 2.100" or bigger intake in RHS or Pro Comp smallblock heads. With the bore sizes they are running I'm sure they are exceeding the limit of the 52% bore to intake size. All and yes they do seem to get them spun up near 8,000 with a little duration cam. But like Mr P Body said they are looking to make torque and through a certain rpm range.
Its been a while since I watched much of the engine master stuff.. but if I recall they are playing in a certain rpm range so what they are doing works great for them to make a ton of torque in the low rpm range... but most if not all of them would be maxed out in rpm at some low point
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Re: Big Ports, Big Flow #s, And Low Duration Camshafts
[Re: MR_P_BODY]
#1727905
01/12/15 04:24 PM
01/12/15 04:24 PM
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Joined: Jan 2003
Posts: 7,498 Minnesota
Hemi_Joel
master
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master
Joined: Jan 2003
Posts: 7,498
Minnesota
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The valve trains in an Engimasters entry are like an Aztec maiden, sacrificed for the cause. .900+ lift, short duration, crazy valve spring pressure. They barely make it thru the contest.
[img]http://i.imgur.com/boeexFms.jpg[/img]31 Plymouth Coupe, 392 Hemi, T56 magnum RS23J71 RS27J77 RP23J71 RO23J71 WM21J8A I don't regret the things I've done. I only regret the things I didn't do. "Wise men talk because they have something to say; fools because they have to say something. ~ Plato"
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Re: Big Ports, Big Flow #s, And Low Duration Camshafts
[Re: BradH]
#1727907
01/12/15 08:51 PM
01/12/15 08:51 PM
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Joined: Dec 2014
Posts: 100 KS
Cogito
member
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member
Joined: Dec 2014
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KS
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Quote:
Big Ports w/ Big Flow #s WITHOUT Big Velocity = Big Pig AND Big Disappointment.
If the head's velocity across the lift curve isn't sufficient, the flow #s don't mean anything and the large(r) runner volume just adds to the problem.
What controls velocity?
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Re: Big Ports, Big Flow #s, And Low Duration Camshafts
[Re: R5P7 Bantam]
#1727909
01/12/15 09:37 PM
01/12/15 09:37 PM
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Joined: Jun 2006
Posts: 5,166 CT
GTX MATT
master
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master
Joined: Jun 2006
Posts: 5,166
CT
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How about a stock cammed Hemi, partiularly the 66/67 grind?
Now I need to pin those needles, got to feel that heat Hear my motor screamin while I'm tearin up the street
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Re: Big Ports, Big Flow #s, And Low Duration Camshafts
[Re: GTX MATT]
#1727910
01/12/15 10:08 PM
01/12/15 10:08 PM
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Joined: Oct 2009
Posts: 1,267 North, Alabama
D-50
pro stock
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pro stock
Joined: Oct 2009
Posts: 1,267
North, Alabama
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My small block was in one of the engine master contest. It did not win but it made 662 hp @ 7300 rpm on pump gas at 394 ci.and has a 255/266 @ .050 roller cam. I do not consider that a whole lot of duration. Heads are Indy 360-2 and flow 337 @ .650 on intake.
1.33 60 ft,6.21 at 110.59 in the 1/8, pump gas small block,2950lbs,drag radials,mufflers and driven to track ...
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Re: Big Ports, Big Flow #s, And Low Duration Camshafts
[Re: HotRodDave]
#1727911
01/12/15 11:15 PM
01/12/15 11:15 PM
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Joined: Jan 2007
Posts: 7,664 IN
ahy
master
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master
Joined: Jan 2007
Posts: 7,664
IN
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Quote:
Look at the cams in the new hemis, high flow, bigish ports and very tiny duration cams give huge HP numbers. You get the best of everything low RPM power and high RPM power without the stupid long duration cams of the 70s. They do get some decent lift but not at the expense of added duration. An average performance cam duration numbers like a comp 280 magnum [Email]230@.050[/Email] would be downright wicked in a 6.1 hydraulic roller.
Another thing to look at and glean information is the engine masters engines and cams, relatively short duration and very high lift with big flow numbers, that seems to be the biggest most consistant part of the recipe the winners use. The winning engines are making incredible TQ per cube and still making very nice HP up stairs.
I love the new Hemi's... they have some tricks that make the setup work. Even the earliest versions benefited from 5 speed OD transmissions with deep first and some stall in the lock up converter. With EFI they would run smooth at cruising RPM... with gears and stall they would scoot. The newest have variable timing and intake length which makes it a much better engine... not as much stall and gear (shifting) needed to cover the weak low end + more on top.
We don't have that available on the wedges. That said, I don't think a "multipurpose" wedge needs more than 240 or 250 degrees duration even with big ports. Drag race, sure, go for duration and get plenty of stall on the converter... but not multi purpose.
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Re: Big Ports, Big Flow #s, And Low Duration Camshafts
[Re: R5P7 Bantam]
#1727912
01/13/15 02:31 AM
01/13/15 02:31 AM
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Joined: Dec 2014
Posts: 100 KS
Cogito
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member
Joined: Dec 2014
Posts: 100
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Quote:
What controls velocity?
Piston speed and port/runner shape. In essence, the geometric profile (tube) in which the air travels to the base of the valve head. This geometric shape starts at the top of the intake manifold (carb plate) and some may include the shape of the venturi's w/in the carb/throttle body.
This is the response I see most often on the internet.
How about valve events and ramp rates?
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Re: Big Ports, Big Flow #s, And Low Duration Camshafts
[Re: Cogito]
#1727914
01/13/15 04:49 PM
01/13/15 04:49 PM
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Joined: Jan 2005
Posts: 12,423 Kalispell Mt.
HotRodDave
I Live Here
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I Live Here
Joined: Jan 2005
Posts: 12,423
Kalispell Mt.
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Wonder why they left out the 340? It would be right there in the middle of the mix with some race headers and big carb, the factory 600 wouldn't hardly flow that and good headers are a proven 25+ hp. Even the 440 hp carb was a big step up in performance.
I am not causing global warming, I am just trying to hold off a impending Ice Age!
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Re: Big Ports, Big Flow #s, And Low Duration Camshafts
[Re: HotRodDave]
#1727915
01/13/15 06:06 PM
01/13/15 06:06 PM
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Joined: Jan 2003
Posts: 9,888 Weddington, N.C.
Streetwize
master
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master
Joined: Jan 2003
Posts: 9,888
Weddington, N.C.
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the thing about a good port is that even if the duration is relatively short, the torque (VE) beyond peak torque RPM does not drop off very rapidly, therefore the motor still makes good/great HP despite having what (on paper) looks like too small a cam. This holds true as long as the induction/compression and exhaust are also suitably matched. Fuel injection has a ton to do with that as well because you only need to move AIR through the manifold (fuel displaces about 7% or so of the available area of a wet port)
The modern Hemi or the Chevy LS2 are very good examples of what an efficient port can do.
I have an '06 trailblazer SS (I use to tow my Mopars) that at 364 cubes makes ~430 at the crank and pushes 4800 pounds to 13.6's at 102+ mph with really only a PCM tune and an electric fan conversion. The cam duration is something like 204/211 @.050
A good port and a small cam will still make great power and very broad torque. Cam timing is a big factor, but it isn't the only way to extend the RPM range.
Where you run into limitations is a proportionally huge port (like a Cleveland Boss 302) on a small displacement motor, it's hard to avoid a peaky (light switch) type torque and power curve with that type scenario. you effectively kill as much duration as you can to try to give it some "passable" bottom end....and (like ford) you gear the wee out of it (4.33 gears, etc).
Last edited by Streetwize; 01/13/15 06:08 PM.
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Re: Big Ports, Big Flow #s, And Low Duration Camshafts
[Re: Streetwize]
#1727916
01/13/15 06:19 PM
01/13/15 06:19 PM
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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:
... Where you run into limitations is a proportionally huge port (like a Cleveland Boss 302) on a small displacement motor, it's hard to avoid a peaky (light switch) type torque and power curve with that type scenario. you effectively kill as much duration as you can to try to give it some "passable" bottom end....and (like ford) you gear the wee out of it (4.33 gears, etc).
That's along the lines of what I was going to add to my original post about how even a "good" head still needs to have enough cubes & compression under it to make the combination effective.
It's another example of a poor parts combination that looks cool on paper, but doesn't pan out in the real world.
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Re: Big Ports, Big Flow #s, And Low Duration Camshafts
[Re: Streetwize]
#1727917
01/13/15 07:34 PM
01/13/15 07:34 PM
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Joined: Dec 2014
Posts: 100 KS
Cogito
member
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member
Joined: Dec 2014
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Quote:
Where you run into limitations is a proportionally huge port (like a Cleveland Boss 302) on a small displacement motor, it's hard to avoid a peaky (light switch) type torque and power curve with that type scenario. you effectively kill as much duration as you can to try to give it some "passable" bottom end....and (like ford) you gear the wee out of it (4.33 gears, etc).
In the hot rod article I posted, the Boss makes more torque sooner, as well as holds onto it longer, than the smaller port DZ. This seems contrary to what you're saying...?
I recently finished a set of LS3 heads going onto a 6.0 similar to yours (G8). They have virtually identical port dimensions as the Victor 440s I'll be using on my car (stock stroke 440). I haven't worked SBM stuff, but from what I've seen for BBMs, I have to think most use heads that are way too small.
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