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  #31 (permalink)  
Old 01-13-2009, 09:16 AM
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Binder,
the article your referencing is WOT 1.5HG A/F mix....

you don't drive at constant WOT on the street!!!!

headers induce a lean mix at part throttle and can cost you TQ....

if it is the same article I am thinking of,,,,cast versus headers showed only 4% gain of the less than max TQ actual at 2600rpms at WOT=adds next to nothing pulling a trailer

only time the headers would help a tiny tiny bit is passing somebody WOT pulling a trailer....

"magazine" articles are totally "biased"
their interest is to sell advertising space...
they never tell the bad or complete story....

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  #32 (permalink)  
Old 01-13-2009, 01:38 PM
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Red, you are WAY to complimentary of magazine articles! I quit subscribing to the rags many years ago and haven't paid attention to the 'technical' articles for longer than that. I look at them at the news stand and occasionally buy one if it has an interesting feature (like a recent Rod & Custom with an article on Ed Roth's Orbitron revival). Correspondents to those mags are really not technically educated people and spew primarily incorrect information. The old days with guys like Jim McFarland who I am pretty sure was a degreed engineer or if not, a self educated one, Tex Smith, etc. who DID have some real knowledge are long gone. All the new tech articles are nowadays are regurgitation of manufacturers installation instructions.

I did my senior project @ Fresno State on header design theory and as you point out, they do definitely make more power at a specific rpm and torque is by definition peaky because the header is designed for one specific rpm. Power by definition fall off pretty dramatically at other speeds. Factory manifolds are designed to not be peaky and have a very flat torque curve which makes Granny and gramps very happy as they cruise to bingo night. That is also a great feature for a tow/cruise car like 49 is building. Binder is correct, 99.999% of our driving could be served extremely well by a 2bbl carb. However the second two barrels are very nice to have when passing a chicken truck on the interstate. My engine is a 331 bored to 354, not a 392. I run a Holley 3-bbl 950cfm carb with primary bore inserts I designed in college to make it a spread bore.



I put a micro switch on the vac secondary actuator arm to see when they opened and they are closed most of the time. The only time they open is for a second or so when I stomp the throttle to pass. I realize I only 'need' a 600cfm carb but it's a GASSER!! "It is so much more important to look good than to feel good!"
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Old 01-13-2009, 01:59 PM
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I want to thank everyone for their posts to this thread. I started it and never expected to get as many postings. If I read between the lines of all of the posts it sounds like for my purposes I am not giving too much on torque when towing the trailer. I do not expect to need WOT to pull the hills. It should be a considerably stronger tow vehicle than my current 4.0 2003 Ranger.
Thanks again to all.
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  #34 (permalink)  
Old 01-13-2009, 02:10 PM
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have you seen these?

http://www.speedwaymotors.com/SandB-...olds,3823.html


it seems to me the biggest restriction in a stock manifold is the donut gasket at the collector. I always use a header flange and header gasket in place of the donut when I run manifolds. I just hate seeing a 2.5 inch output choked down to 2 inches. The above manifolds use a standard header flange. Expensive but looks like a good flowing manifold.
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  #35 (permalink)  
Old 01-13-2009, 02:48 PM
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your welcome 49willard,,,

what is critical for your application is tranny gears ratios and rear gears ratio choices (and tires diameter)....

flywheel TQ X tranny ratio X rear ratio=actual force applied to the tires

illustrations only:
300ft/lbs x 2.46 first gear x 3.50 rear gear=2583 ft/lbs on the tires
300 x "3.08" first gear x 3.50=3234 ft/lbs twisting the hides!!!
300 x 2.46 x "3.73" rear gears=2752 on the tires
300 x 3.08 x 3.73=3446 ft/lbs,,,,approx 1000ft/lbs more force on the tires at around 2,000rpms accelerating normal from a stop sign!!!!
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Old 01-13-2009, 05:33 PM
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Quote:
Originally Posted by red65mustang
Binder,
the article your referencing is WOT 1.5HG A/F mix....

you don't drive at constant WOT on the street!!!!

headers induce a lean mix at part throttle and can cost you TQ....

if it is the same article I am thinking of,,,,cast versus headers showed only 4% gain of the less than max TQ actual at 2600rpms at WOT=adds next to nothing pulling a trailer

only time the headers would help a tiny tiny bit is passing somebody WOT pulling a trailer....

"magazine" articles are totally "biased"
their interest is to sell advertising space...
they never tell the bad or complete story....
Hmmm. Interesting thread. What started out as a thread asking about manifolds since headers wouldn't fit, has turned into a header bashing thread where exhaust manifolds are claimed to do it all. From tow vehicles to zz430 equipped 11 second street/strip vehicles, cast iron is all you need.

No, I don't constantly drive at WOT on the street. But that's not the point. The point is that several people have been claiming that headers only add power waaaay above what street motors will see. Or that speed parts only add power above 4000rpm. Is 3400rpm waaaay above what street motors see on the street? It's certainly below 4000rpm.

I didn't realize it was somehow unfair to mention WOT operation. I mean, sure, if we want to caveat it so that we are only talking about engines that only operate at part throttle and never see the far side of 2k rpm, then I agree 100%; cast iron exhaust manifolds are the only way to go.

But then, I can think of more than one occasion when I've pulled out of a truck stop to merge into freeway traffic on a steep grade with a heavily loaded vehicle I've had to floor it and operate above 2k rpm. Even in my Scout. Especially in my Scout.

I must be doing something wrong, as I can not "live" at part throttle below 2k rpm. Not even in my tow vehicle. Probably because, like most tow vehicles, I don't always use it just for towing.

Quote:
I did my senior project @ Fresno State on header design theory and as you point out, they do definitely make more power at a specific rpm and torque is by definition peaky because the header is designed for one specific rpm. Power by definition fall off pretty dramatically at other speeds. Factory manifolds are designed to not be peaky and have a very flat torque curve which makes Granny and gramps very happy as they cruise to bingo night.
Again, granny and gramps are cruising to bingo at 45 mph in the fast lane on the freeway. And cast iron manifolds are just dandy for that transportation appliance holding up traffic on the way to bingo after hitting the early bird senior special at the local Denny's. But what they were really designed to do (the cast iron exhaust manifolds, not granny & gramps) was (a) be cheap to produce (b) be durable (c) fit into the engine compartment permitted by the designers who sculpted the outside of the car (d) produce adequate power. In that order. No more engineering effort was expended once adequate power was achieved. I simply do not believe that cast iron manifolds will somehow "take over" and start outflowing headers above the specific rpm the headers were designed for.

And I'm demonstrating I have a sense of humor when I talk about the type of cheap unequal length headers people order from Jegs and Summit as if they are carefully "tuned."

Last edited by BinderDriver; 01-13-2009 at 10:22 PM.
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  #37 (permalink)  
Old 01-14-2009, 07:28 AM
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No argument from me on all your points. I run headers on all my modified cars, I believe they have benefits, mainly because they look good! However it is undeniable that they are 'peaky', not because of how they flow but because of the 'organ pipe' pressure waves that are the reason they give the boost in performance they do. Those pressure waves travel at the speed of sound so do their deed at a given rpm. At other speeds they are arriving too quickly or to slowly so can do more harm than good. Factory manifolds are designed to have no organ pipe waves so they don't benefit or suffer from them. Thus they tend to have a nice flat torque curve, great for normal driving, towing, etc., and flow fine for any normal engine speed. Grated @ high speed WOT they begin to build back pressure and if you want to run there often by all means, upgrade to headers and free flowing system. Most medium to large V8s have enough power to tow, but not to win red light bandit encounters. As I always say, engine design is a series of compromises, there is no perfect engine for every driving condition.
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  #38 (permalink)  
Old 01-14-2009, 10:16 AM
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There are a bunch of things on this thread that I am not going to comment about.

Fact of the matter is, IF headers are matched to the engine and the intent PROPERLY, then headers make more power everywhere across the board, increase efficiency and improve fuel mileage.

Problem is that MOST hotrodders believe that more is better, bigger is better, and everything should be designed for the ultimate power possibility.
90% of headers are designed to make power at higher rpms. When is the last time you saw anyone use a 1 1/2 primary on a 350?

Headers can be compared in principle to carburetors, camshafts, or wheels/tires.
TOO BIG IS JUST TOO DAMN MUCH.

That old idea that "who cares how it runs down low as long as it screams at 6500 rpm" hot rod idea is for kids.

If power is really a concern then GET THE PROPER HEADER and exhaust system.

One other thing that bears mentioning.
96% of every torque curve graph you see has a significant dip in the lower 3000 rpm range right where we need more. Ever wonder why?

It is not because Westech and other dyno people are stupid, ignorant, lying, magazine hacks that are out to screw the public.

JMO
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  #39 (permalink)  
Old 01-14-2009, 10:18 AM
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Quote:
Originally Posted by willys36@aol.com
Red, you are WAY to complimentary of magazine articles! I quit subscribing to the rags many years ago and haven't paid attention to the 'technical' articles for longer than that. I look at them at the news stand and occasionally buy one if it has an interesting feature (like a recent Rod & Custom with an article on Ed Roth's Orbitron revival). Correspondents to those mags are really not technically educated people and spew primarily incorrect information. The old days with guys like Jim McFarland who I am pretty sure was a degreed engineer or if not, a self educated one, Tex Smith, etc. who DID have some real knowledge are long gone. All the new tech articles are nowadays are regurgitation of manufacturers installation instructions.

I did my senior project @ Fresno State on header design theory and as you point out, they do definitely make more power at a specific rpm and torque is by definition peaky because the header is designed for one specific rpm. Power by definition fall off pretty dramatically at other speeds. Factory manifolds are designed to not be peaky and have a very flat torque curve which makes Granny and gramps very happy as they cruise to bingo night. That is also a great feature for a tow/cruise car like 49 is building. Binder is correct, 99.999% of our driving could be served extremely well by a 2bbl carb. However the second two barrels are very nice to have when passing a chicken truck on the interstate. My engine is a 331 bored to 354, not a 392. I run a Holley 3-bbl 950cfm carb with primary bore inserts I designed in college to make it a spread bore.



I put a micro switch on the vac secondary actuator arm to see when they opened and they are closed most of the time. The only time they open is for a second or so when I stomp the throttle to pass. I realize I only 'need' a 600cfm carb but it's a GASSER!! "It is so much more important to look good than to feel good!"
Wow! A Holley 3 barrel. I remember when these came out. Thanks for reminding me how old I've become.



Bogie
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  #40 (permalink)  
Old 01-14-2009, 12:34 PM
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Binder,
it's "real world" actual results that count,,,

illustration for this thread:
assuming 8300lbs (truck and trailer) and 350HP with stock manifolds he will arrive at the end of the 1/4 mile interstate on ramp in 16.6 seconds at 81mph....
same 8300lbs and same motor,,, 370HP with headers he will arrive in 16.3 seconds at 82 mph...

(blink your eye's very quickly, that is approx 1/10th second)
3/10ths of a second in the real world is nothing...
one mph faster merging into traffic is basically nothing.....
(magazines never tell the whole story!)

you can use this simple WOT calculator to get a idea of what any given weight to power ratio change does do....

http://www.tciauto.com/Products/Tech...culators.asp#1

I'm not intending to bash headers either....
depending on the car/motor combo and application they can be a top priority or a last priority...
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  #41 (permalink)  
Old 01-14-2009, 02:07 PM
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Quote:
Originally Posted by ScoTFrenzel
There are a bunch of things on this thread that I am not going to comment about.

Fact of the matter is, IF headers are matched to the engine and the intent PROPERLY, then headers make more power everywhere across the board, increase efficiency and improve fuel mileage.

Problem is that MOST hotrodders believe that more is better, bigger is better, and everything should be designed for the ultimate power possibility.
90% of headers are designed to make power at higher rpms. When is the last time you saw anyone use a 1 1/2 primary on a 350?

Headers can be compared in principle to carburetors, camshafts, or wheels/tires.
TOO BIG IS JUST TOO DAMN MUCH.

That old idea that "who cares how it runs down low as long as it screams at 6500 rpm" hot rod idea is for kids.

If power is really a concern then GET THE PROPER HEADER and exhaust system.

One other thing that bears mentioning.
96% of every torque curve graph you see has a significant dip in the lower 3000 rpm range right where we need more. Ever wonder why?

It is not because Westech and other dyno people are stupid, ignorant, lying, magazine hacks that are out to screw the public.

JMO
Yep, engine design is a compromise. However tube diameter doesn't have any bearing on the tuning speed of the header, nor do the number of turns in a tube, within reason. The only parameter of a 4-tube header that determines the max benefit point is tube length. Diameter is important in that too small a tube results in top end pressure losses and too large a tube results in the pulse energy being dissipated and lowered effectiveness, still at the same tuned rpm.

In my college work on header and intake design there are speeds in a 4-tube header where power is significantly below a stock manifold. I built a port pressure manometer (measured pressure essentially at the exhaust valve over the 4 cycles of a single cylinder every degree of rotation for all 720deg) and monitored these pressure trends over many rpm ranges for many header designs. A header is designed to achieve as low a port pressure as possible the instant the exhaust valve closes. With a stock manifold, this port pressure is always positive but never varies much => a flat torque curve. However with a tuned header the length could be varied to achieve a large reduction in port pressure => scavenging of the cylinder => significant power increase at a desired max power rpm. Down side is that the negative pressure wave is offset by a large positive pressure wave at another rpm. I did this on a dyno so I could correlate port pressure to engine power output. As you might expect there is a direct relationship between port pressure and horsepower. Low pressure st design rpm gave a power increase, inevitable high port pressure at other rpms gave a power decrease.

Intake runners can be designed exactly the same except they are designed to achieve the highest maximum intake port pressure the instant the intake valve closes. Again, such tuned runners bring with them a complementary very low pressure port at an offsetting rpm. That is the principle behind the shoe-box plenum manifolds (short for high speed WOT boost), the old '50s Chrysler cross ram manifolds (very long for idle to 2000 rpm boost) and stacks on injected racing engines (short again for top end boost). Nothing is free!!
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Old 01-14-2009, 07:37 PM
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If I have a 1 1/2" diameter primary that is 30" long, and a 1 3/4" diamater primary that is also 30", the smaller pipe will produce a faster moving exhaust pulse, thus having greater momentum, thus will "pull" or scavenge the following exhaust pulse out of exhaust port, moreso than a slow moving pulse.

the smaller tube will have a lower torque band than the larger diameter primary.


My point is BOTH primary tube diameter AND length must be considered.

Discussion?

I noticed good gains off idle up in my 97 Vortec 350 truck with Hooker 2462 1hkr 1 5/8"x2 1/2" headers, both at part throttle and at WOT.

peace
Hog
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  #43 (permalink)  
Old 01-14-2009, 10:51 PM
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Nope. The pressure pulse (shock wave) with which the header is tuned moves at the speed of sound and is independent of the speed of the flowing gas. The 'compact' smaller tube definitely maintains the energy of that pulse but does not affect it's velocity. Length of the primary tube is the only consideration in tuning the header for the rpm range. Diameter comes into play in balancing maximum signal strength while minimizing friction flow losses. For 4-tube headers the collector only needs to be large enough to provide a volume for the pulse from the individual tubes to be independently reflected back up the tube without interference from the adjoining tubes. When the exhaust valve opens, a positive pressure pulse travels down the tube at the speed of sound. When it reaches the collector, it catastrophically expands sending a negative pressure pulse at the speed of sound back up the tube. You want that negative pressure pulse to reach the exhaust valve just as it is closing which 'supercharges' the cylinder by scavenging exhaust gas out and sucking more unburned fuel in. All during that time the gas is flowing down the tube at a much, much slower speed than all the shock waves. Since the speed of sound is a constant at a given gas composition and temperature, the tuned speed is solely a function of the length of the pipe to allow two traverses of the tube by a shock wave between the time of valve opening and closing.

Tri-Ys use a little different application of this organ pipe or Hemholtz resonator technology but the principle of shock wave @ the speed of sound determining tube length still holds true.

Fairly available suggested reading on this topic are

Huntington, Roger: "Carb Ram Duction", Car Craft, Vol. 14, Num. 5, August 1966, p. 38-42.

Kopper, John B.: "Intake and Exhaust Tuning", Road and Track, Vol. 17, Num. 9, May, 1966. p. 93-98.

Smith, Phillip H.: The Scientific design of Exhaust and Intake Systems, Cambridge, Mass., Robert Bently Inc., 1970.

All the above should show up on ebaY from time to time. The first two are REAL technical magazine articles by educated men, not the ignorant ramblings of the 'tech' articles in modern car mags. Huntington for sure you can take anything he wrote over the years to the bank.

The book is an an exhaustive coverage of the topic and a necessary primer for anyone truly interested in delving deeper into the topic.

I have several technical papers on the subject from ASME conferences but unfortunately ASME destroys all their technical papers after a time period and they are no longer available.
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Old 01-15-2009, 10:13 AM
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Hog,
"if" the small diameter/higher velocity exhaust and "cam events" are tuned together so that the overlap period does add to the low rpms intake vacuum Hg/velocity for a better cylinder fill % below the initial TQ peak,,,it will add to the TQ....
(excellent for a fixed (low) rpms motor, more power with less gas at lower rpms for longer life)

that's a part of why the oems are moving towards variable valve timing....,,,,intake/exhaust demensions are a fixed compromise so,,, change the cam events to better match the load/rpms and velocity/cfm...

my $.02
fair chance the majority of difference you are actually feeling is due to improving the exhaust flow,,,pipes and mufflers,,,(oem stuff is a terrible compromise).....
(if you don't have a "H" pipe,,,do add one)

stock pick up trucks are geared much lower than cars so most of your driving is at higher rpms per mph where headers will help....
further helped by the pick up motor is cammed and timed to make MAX TQ per rpms at least rpms possible....
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Old 01-15-2009, 10:28 AM
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Fact of the matter is,

Hundreds of dyno tests have shown that smaller primary diameter favors lower rpms. It works on the vehicle also.
This has nothing to do with what comes aft of the collector length.

You don't have to understand why,
you just have to know that it DOES.
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