What size headers for my car?

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  1. #1

    Default What size headers for my car?

    Been going back and forth all winter long. Done a bunch of searches and reading. Car makes 24.75lbs of boost with a 2.9 whipple. 3.5 upper, 4lb lower. Goals are more power and lessen the boost. Car currently makes 675rwhp. Fuel system is gt pumps, 60lb injectors. Stock K member will be used with an aftermarket steering shaft. Brand will be ARH. For the power levels I'm at, will the 1 3/4 be enough? Or skip to the 1 7/8?

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  3. #2

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    1 3/4" primaries, 3" collector will serve you just fine with the power that the 2.9 is capable of making.

  4. #3

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    Quote Originally Posted by Helomech74 View Post
    1 3/4" primaries, 3" collector will serve you just fine with the power that the 2.9 is capable of making.
    How much do you think the boost will drop?

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  6. #4
    Senior Member Array cobraracer46's Avatar
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    The answer to your question is to stick with the factory cast iron exhaust manifolds.

    Here is a terminator with the factory returnless fuel system, Factory cast iron exhaust manifolds and catalytic converters that put down over 700 HP to the tire thus proving that headers are not a requirement for big power. What it required for big power is a blower that moves enough air.



    http://www.mustangandfords.com/how-t...th-blower-kit/

  7. #5

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    Quote Originally Posted by cobraracer46 View Post
    The answer to your question is to stick with the factory cast iron exhaust manifolds.

    Here is a terminator with the factory returnless fuel system, Factory cast iron exhaust manifolds and catalytic converters that put down over 700 HP to the tire thus proving that headers are not a requirement for big power. What it required for big power is a blower that moves enough air.



    http://www.mustangandfords.com/how-t...th-blower-kit/
    I was warned about you hahaha. Thanks for trying to talk me out of it. Install is not a problem, and neither is price.

  8. #6
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    Why is Cobraracer46 allways in every forum infecting questions about long tube headders??
    It's quite obvious that a engine is a airpump, what comes in must come out.
    If it comes out easier, that's much better.

  9. #7
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    Quote Originally Posted by Tbird View Post
    Why is Cobraracer46 allways in every forum infecting questions about long tube headders??
    It's quite obvious that a engine is a airpump, what comes in must come out.
    If it comes out easier, that's much better.
    Yes, an engine can make 700hp without headers, but they will make any supercharged combo more efficient.

  10. #8
    Senior Member Array cobraracer46's Avatar
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    Quote Originally Posted by na svt View Post
    Yes, an engine can make 700hp without headers, but they will make any supercharged combo more efficient.
    If we look at what Ford has done with factory "supercharged combo's" on the MOD motor V8 starting with the Terminator and moving onto the Ford GT, GT500, etc, you will notice that all of the design and enginerring work centered around the cyclinder heads, intake, valve train, accessory drives, etc, while the cast iron exhaust manifolds carried on virtually unchanged so that tells us that the notion of headers making any supercharged combo "more efficient" is a hypothesis that is not supported by the engineers over at Ford.

    One final point, if headers will make a mod motor supercharged combo " more efficient," I'm assuming that you are suggesting that headers will significantly increase power on a supercharged mod motor V8. Therefore, I would offer the opportunity for any one to back up the claim that "headers make any supercharged combo more efficient" by conducting a horse power test where the air full ratio, temp, and other conditions remain the same with the only change being that the factory cast iron exhaust manifolds are swapped over for headers and no other changes are made such as " headers and tune", headers and pulley, headers and mid pipe and then finish the test by documenting the results.

    It's worth noting that in supporting a claim that headers make more power or will make " any supercharged combo more efficient" it's important to follow sound scientific principles and Ford engineering discusses this concept in great detail below:

    To quote Ford:

    " DYNAMOMETER TESTING AND FORD RACING CALIBRATIONS
    sensitivity of torque relative to ignition timing. Basically this means that the closer the actual conditions are to the SAE J1349 standard (77 deg F inlet air, 29.31 inHg barometric pressure), the more comparable the results are to those quoted by the manufacturer. Unless otherwise explicitly stated, all horsepower numbers in the Ford Racing catalog have been determined by using the
    SAE J1349 standard.
    When testing a particular calibration or performance-enhancing part by performing back-to-back dyno runs, it is critical to keep
    test conditions as similar as possible between the runs. This sounds obvious, but is very commonly overlooked by many aftermarket companies who frequently publish dyno charts depicting large gains, but fail to give all the necessary data to show the tests were run under similar conditions. In order to be certain that the test conditions are as similar as possible, the following data is mandatory and needs to be collected for each run:
    • Ambient air temperature
    • Barometric pressure
    • Inlet air temperature (on a forced-induction car, this is usually downstream of the power adder)
    • Air/fuel (A/F) ratio (preferably upstream of any catalyst)
    Truly meaningful power numbers cannot be collected without this data!


    It is also a good idea to make sure the A/F ratio sensor (often called a “wideband” sensor) in use on the dyno has not been exposed to leaded fuel and has not been in service for an excessive period of time (greater than six months, depending on frequency of use). A/F ratio is the single most important parameter to measure accurately when doing any sort of dyno tuning, so it is critical the sensor is providing accurate information. When doing any PCM calibration on a dyno, the resulting calibration will only be as good as the A/F sensor.
    These additional inputs should be used for ideal dyno testing and calibration: • Air/fuel ratio and spark advance commanded by the PCM
    • Fuel injector pulsewidth
    • Fuel pump duty cycle (in the case of ERFS)
    • MAF sensor voltage
    • Fuel pressure
    • Engine oil temperature
    • Differential oil temperature"


    Here is an important about misleading results:

    "How calibration can cause misleading dyno results:
    Production calibrations have an inferred catalyst temperature protection model which constantly calculates the temperature in the hottest part of the hottest catalyst. This calculated temperature is based on many PCM parameters, such as engine speed, load, ingested air mass, time, inlet air temperature, EGR flow rate and many others.
    When the catalyst model calculates that the catalyst temperature is about to exceed a level that is safe for the catalyst (generally around 1650 deg F), the PCM will richen the A/F mixture as necessary to lower the exhaust gas temperature and cool the catalyst. This richened A/F ratio will decrease power output, but is absolutely necessary to keep the catalyst from being permanently damaged. Unless A/F ratio is monitored during a dyno pull, the dyno operator will have no idea when catalyst temperature protection has been invoked and can make erroneous conclusions with regard to power output.
    As a trivial example of how this can affect dyno testing, consider a supercharged production vehicle with production calibration performing back-to-back runs under identical conditions except as noted. The car is driven to a dyno facility and immediately put on
    the dyno and a run is performed, yielding a result of 420 hp. In this example, A/F ratio is not monitored. A part is swapped for another “high-performance” part and another dyno run is performed, resulting in 430 hp. The dyno operator concludes the “high-performance” part is worth 10 hp. This is not accurate because when the car was first dyno tested, its catalysts were sufficiently hot that catalyst temperature protection was invoked during the dyno pull which reduced power output by richening the A/F ratio. While the car was having the parts swapped, the catalysts cooled down enough that during the next dyno pull catalyst temperature protection was not invoked. The engine made more power on the second pull because it was running a leaner A/F ratio closer to optimal and not necessarily because of the “high-performance” part. If the dyno operator was monitoring A/F ratio, this would have been readily apparent.
    If the operator was monitoring the A/F ratio commanded by the PCM, the activation of catalyst temperature protection would become self-evident. In this example, the erroneous conclusion that was reached suggested the “high-performance” part was worth 10 hp when it really wasn’t, but the opposite can also occur quite easily. Without covering every possible scenario, it will suffice to say that dyno numbers are ONLY meaningful when supporting data such as A/F ratio, inlet air temperature and the others listed above are
    also provided.
    There is also a model for oxygen sensor protection and exhaust valve protection that when not taken into account can cause misleading dyno data. In general, exhaust temperatures greater than about 1650 deg F can damage exhaust valves, and extreme care is
    taken in production calibrations to ensure that sustained engine operation beyond that temperature does not occur. This is rarely
    an instantaneous failure but rather one that over time “tulips” the exhaust valves and ultimately will fail the engine.
    Aftermarket cold air kit manufacturers that claim to work without the need of a PCM recalibration are a common source of misleading dyno power claims. Some of the manufacturers of these kits claim enormous power gains using nothing but their kit and a production calibration. Most of these claims are not supported with A/F, inlet temperature or spark advance traces during the dyno pulls that
    are shown in their advertising. In some cases, the apparent increase in power is due to differing dyno test conditions as mentioned previously, while in other cases they can be due to the fact that the MAF sensor transfer function in the PCM is left stock. If the cold air kit flows more air and the MAF transfer function in the PCM is stock, it will not “know” about the extra air that’s entering the engine. This will result in the engine running an A/F ratio that is leaner than it should be for engine durability. While this has the potential to produce more power, it can also be potentially damaging to catalysts, exhaust valves, piston rings and other engine components. The commanded spark advance can also be incorrect and result in detonation or pre-ignition with potentially catastrophic results. One should be very suspect if a particular cold air kit claims a huge power increase over stock at low engine rpm and without a calibration. Air inlet restrictions generally only become significant at higher airflows, so if a claim is made that a cold air kit increases torque at 2000 rpm without the aid of a calibration, you can be sure that varying dyno test conditions or a significant change in A/F ratio are the cause.

    Ask for more supporting data!

  11. #9

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    Cobra Jet has headers with dumps. That shows you what ford does with a max effort car trying to squeeze out more power. Seems like your statement below is misleading at a minimum:

    "the notion of headers making any supercharged combo "more efficient" is a hypothesis that is not supported by the engineers over at Ford."

    Name:  cobra-jet-engine-876.jpg
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    As far on header size you might find this video interesting:



    It's not a SC Modular Ford but I think it is interesting and gives you something to think about.

  12. #10

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    Ford uses cast iron manifolds for durability in supercharged apps and also because the converter location has to be close to the cyl head for emission purposes.
    People often say "well Ford did this blah blah blah... Ford does things for a host of reasons primarily emissions then durability.

  13. #11
    Senior Member Array IWRBB's Avatar
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    That horse is long since dead guys.

    https://www.modularfords.com/threads/...t-Supercharger

    Headers are a 2nd order effect. They drop the boost and yield nearly the same HP. Up the blower speed to get back to the same boost level and you'll get a healthy HP bump compared to manifolds. Done.

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    Quote Originally Posted by speeddemon2000 View Post
    "the notion of headers making any supercharged combo "more efficient" is a hypothesis that is not supported by the engineers over at Ford."
    Why do you make such a blasphemous comment? A longtube header that is properly sixed for the engine will always be more efficient than a stock manifold. The fact that Cobras had cast iron manifolds from the factory does not mean they are better than longtubes.

  15. #13
    Senior Member Array oldmodman's Avatar
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    Just to churn the waters a little more.
    Here is a thread I did on how much effect a dent has in your headers.
    Look at the dyno results from pounding the crap out of the headers. Almost none. Until they were smashed beyond belief.
    I was very surprised when I watched it. it goes against everything I "wanted" to believe.

    https://www.modularfords.com/threads/...Any-Difference

  16. #14

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    Quote Originally Posted by na svt View Post
    Why do you make such a blasphemous comment? A longtube header that is properly sixed for the engine will always be more efficient than a stock manifold. The fact that Cobras had cast iron manifolds from the factory does not mean they are better than longtubes.
    I agree with what you are saying. I was disagreeing with cobraracer46's comments which I put in quotes.

  17. #15
    Senior Member Array cobraracer46's Avatar
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    "That horse is long since dead guys. https://www.modularfords.com/threads/...t-Supercharger Headers are a 2nd order effect. They drop the boost and yield nearly the same HP. Up the blower speed to get back to the same boost level and you'll get a healthy HP bump compared to manifolds. Done.


    Headers are a 2nd order effect. They drop the boost and yield nearly the same HP. Up the blower speed to get back to the same boost level and you'll get a healthy HP bump compared to manifolds. Done.
    In regards to following sound scientific testing principles, a logical conclusion or cause and effect can only be determined when only one condition at a time is tested. In other words, if two changes done at once, determining which component is responsible for the cause and effect is impossible.

    Here are some tests you might want to try: only change the boost and see what the data says. Run another test where the only change is the headers and then read the results. Finally, I keep hearing the term " headers make any combo more efficient." How do you define efficiency and what kind of testing do you run and what kind data do you use to define it? What kind of statistical analysis do you use to determine a significant change?????
    Last edited by cobraracer46; 02-23-2016 at 11:22 AM.

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