differance between shorty and full length headers

[grumpyvette]

read, the linked info, because understanding the concept and the correct use of the linked calculators will effect your engines power curve, doing it correctly helps to provide a wide power band, doing it wrong tends to significantly reduce power potential.
now keep in mind if your cam timing does not match your headers intended scavenging power range, and the rpm its designed for , the engines displacement and intake flow rates, so that all factors are designed to maximize flow in a set rpm band and flow rate, (IE, complement each other) you'll have a marked reduction in the power potential,
and NO header will function correctly with significant back pressure beyond the header collectors
in most applications
if both collectors feed an X pipe in front of a very low flow restriction exhaust, you widen the power curve,
in an ideal world, the x-pipe is withing 18"-24" of the collectors exit

, on the extremes ,I've seen several dyno tests where carefully tuned headers allowed to engine to produce 50-70 more horse power, than the stock exhaust manifolds, and I've seen tests where adding a restrictive exhaust to open headers resulted in 70-80 horsepower losses,, as in most component choices selecting the correct matching parts adds a good deal to the results but mis-matched components can hurt your power curve noticeably.
that one reason you need to read dyno tests in magazines very carefully, because its rather easy to make any headers or exhaust, cam, or intake manifold look good or bad by simply carefully selecting the parts... in the test that they are compared too, by carefully selecting the other components that favor the parts your trying to sell or parts the restrict the competitions components, from reaching their potential.
a great set of tuned headers on a killer engine combo with a restricted exhaust, or a mis-matched cam, or a mis-match intake will show little if any power gains, and removing those components, and swapping in the correct matched components will boost hp on even mediocre headers.

The question always comes up about , choosing the header primary pipe diameter, as in should you get 2" or 2.125" or 2.25" primary's headers on that big block, or 1.675" ,or 1.75" on your small block ETC. the rule of thumb is to match the exhaust port size or use only slightly larger, the restriction the exhaust system you place behind any size header will pose a much greater chance of costing you potential performance than the change in primary pipe diameter, in most cases simply because most commercial headers are designed more for low cost and ease of production than to maximize performance.
Now that does not mean you can't get good commercial headers or that your choice in header type, diam. or length won't effect your results, but unless you match the header design that you install to the application, displacement, compression, cam timing and other factors your already working at a disadvantage.

GRUMPY?

From what I was reading having the header inlet smaller than the exhaust port is a very bad thing... I was hoping to run the factory exhaust for a short time, mostly during camshaft break-in and for me to pay down my credit card for a month or two...
Thoughts?

I find this graph very useful, it shows stock corvette exhaust manifolds vs headers on the same 496 BBC engine dyno test

I think 99.8% of the guys in this hobby are forced to work on a rather limited budget, your certainly not alone in that regard, so I would not be all that worried about breaking the cam in or running it awhile with restrictive stock exhaust manifolds,
while its certainly true it will cost you peak horse power below about 4000 rpm its restrictive effect won't be all that critical if the rest of the exhaust systems not all that restrictive, keep in mind headers are designed to increase cylinder scavenging efficiency and as the rpms increase both the volume of the exhaust gases exiting the engine (goes up rapidly) and the time lag between cylinders firing changes (gets far shorter) thus the volume of gases and the cross sectional area restricting the gas flow becomes much more restrictive and the ability of the inertia of those gases effect to help drag the mass of following exhaust pulses tends to become more effective in a properly tuned header and collector as the rpms increase
ONLY IF THE EXHAUST SYSTEM PAST THE HEADERS COLLECTOR IS VIRTUALLY NON RESTRICTIVE, TO EXHAUST FLOW IN THE HEADERS DESIGNED RPM OPERATIONAL POWER BAND,
which is almost always found in the 3500rpm-7500rpm range and covering generally a 1500rpm-2000rpm wide rpm ,
sweet spot where its most efficient.
your engines rpm range, compression, displacement, cam timing, header primary length and cross sectional area, plus the fuel/air ratio, intake manifold design, carburetor, or throttle body flow rates, ignition timing and several other factors will effect your engine performance and how effectively headers scavenge the cylinders

A COUPLE HOURS SPENT READING CAN SAVE YOU MONEY AND EFFORT

the one thing you should rapidly come to realize, if you compare the suggested dimensions vs the measured dimensions,
is that most lower cost headers are designed with ease of manufacture,and low cost, as the prime criteria,
and significantly shorter and smaller diameter primary and collector dimensions,are used,
than might be ideal ,to allow a single header design to fit as many different chassis applications as can be done,
with a single nearly interchangeable design, to simplify both marketing and inventory reduction


http://garage.grumpysperformance.com/index.php?threads/calculating-header-design.185/

http://garage.grumpysperformance.com/index.php?threads/header-dimension-calculator.15013/

http://www.hotrod.com/articles/headers-dyno-test/

http://www.superchevy.com/how-to/148-0404-best-headers-shootout/

http://www.superchevy.com/how-to/49178-headers-power-increase/

http://www.mustangandfords.com/how-to/engine/29618-short-long-tube-headers-test/

http://www.carcraft.com/techarticles/header_basics/

http://www.sandersonheaders.com/Lets-Get-Technical.html

http://www.airflowresearch.com/hot-rod-nov-2013-305cc-bbc.php

you will occasionally see dyno test results similar to this, that show about a 20 hp spread in the power curve, that seem to indicate that the difference in header configuration is not overly critical,but keep in mind these results are almost always done on 350-383 displacement engines with fairly mild compression , below 9.5:1 and fairly low duration cams ( example ,below 230 deg @.050 lift )and stock or mildly restricted exhaust systems, an engine with a fairly tight LSA and high compression and a low restriction or open exhaust can take full advantage of the headers scavenging the cylinders in a tuned rpm range significantly boosting the power produced, the tuned exhaust header has a greater effect on a higher compression ratio engine of larger displacement with a tighter LSA cam
http://www.bgsoflex.com/bestheader.html

http://www.wallaceracing.com/header_length.php

http://maxracesoftware.com/pipemax36xp2.htm

http://victorylibrary.com/mopar/header-tech-c.htm

http://garage.grumpysperformance.com/index.php?threads/building-custom-headers.961/



http://maxracesoftware.com/pipemax36xp2.htm

http://stockcarracing.automotive.com/49 ... sions.html

http://www.carcraft.com/techarticles/03 ... index.html

http://www.racingbeat.com/2001header/headertest.htm

http://www.carcraft.com/techarticles/he ... usion.html

http://www.hotrod.com/techarticles/engi ... index.html




shorty or block hugger designs

long tube full size headers

theres a great deal of info on the site about selecting or building headers, but one major factor is that a NON-RESTRICTIVE exhaust system MUST be installed with ANY HEADERS to allow them to work correctly. for headers to work correctly they require an exhaust pulse to allow its inertial energy to drag the following charge along with it out the exhaust.
if you can,t visualize that it might help to find a 3 ft long section of 2.5" pvc pipe and wrap a bit of tape around a full coke can so it slides easily thru the PVC, pipe but fills its interior diam., now place the pipe horizontally insert the coke can and drop the opposite end strait down while you hold your hand over the end the coke can was inserted into, as the mass of the coke can falls you'll feel air dragged with it , the same basic thing happens with an exhaust pulse, its mass is far less but its traveling much much faster, and depending on the rpm and displacement it does generate significant energy that can be used to draw the next intake runners charge into the cylinder as it draws out the next exhaust charge during the cams overlap duration (LOOK INTO CAM TIMING)
keep in mind the LENGTH of the header tube effects the rpm levels and energy transferred as it takes time for that mass of hot exhaust gas to travel thru the primary tube, naturally a longer distance tends to require a longer time and the longer duration tends to impart a longer and stronger negative pressure wave to assist the next pulse IF ITS TIMED CORRECTLY and the header primary tube is the correct dia. and length for the engines displacement,compression, cam timing, and several other factors, but again, it works far more effectively if the exhaust system is a low restriction design that doesn,t reduce the scavenging effect of the pulse waves, and the tubing is long enough to work effectively

viewtopic.php?f=52&t=1070

viewtopic.php?f=52&t=333

viewtopic.php?f=52&t=480

viewtopic.php?f=56&t=352

viewtopic.php?f=56&t=1166

http://www.slowgt.com/Calc2.htm#Header

http://www.bgsoflex.com/auto.html

viewtopic.php?f=80&t=10730&p=46843#p46843

these threads might help

http://www.pontiacracing.net/js_header_length1.htm

this MELROSE
exhaust is well designed and should give a good idea as to what your trying to do,when building a custom exhaust,or if your not into welding and fabrication you could buy one

http://www.melroseheaders.com/products/ ... ms/c-4.php

a well thought thru design on an (X) pipe and cut outs

keep in mind headers loose a great deal of their potential horsepower gains if there matched up to a restrictive exhaust

http://www.melrosecorvette.com/1984-199 ... ic-option/

INSTALLING AN (X) PIPE IN THE EXHAUST ON A DUAL EXHAUST CAR

keep in mind that a properly designed exhaust system and headers goes a very long way towards increasing the efficiency of the intake manifold and head flow , and remember that the better the heads and the more effective the exhaust scavenging the less duration the cam used will require!
what goes in, needs to flow out with near zero flow restriction

adding an anti-reversion baffle to a 18"-24" longer collector on open headers with the internal pipe about 1/2 the collector length tends to help scavenging on some engines

if you want max engine performance under predictable conditions,
it will take some testing, measuring and thought,
could you give us some idea as too,
engine displacement"
bore and stroke ?
connecting rod length,
engines intended power band?
transmission shift points?
the cam timing, (lift ,duration)?
cylinder head flow rates,?
static compression ratio,?
ignition advance curve,?
intake valve diameter?
intake port cross sectional area?
intake runner length?
exhaust valve diameter?
, and header primary tube diameter?
and length?
fuel/air ratio every 1000 rpm?
exhaust back pressure in the collector every 1000 rpm?
intake plenum vacuum every 1000 rpm?
with that data we can stop random guess work,
and have at least some facts to work with,
to make a semi logical guess as to what changes might help.
guessing is fast and easy, getting a few facts and working out the details is a bit harder but more productive

http://www.wallaceracing.com/Calculators.htm

http://garage.grumpysperformance.com/index.php?threads/calculating-header-design.185/

http://garage.grumpysperformance.com/index.php?threads/building-custom-headers.961/

http://garage.grumpysperformance.co...ful-exhaust-valve-size-and-header-info.11265/

http://garage.grumpysperformance.com/index.php?threads/dyno-testing-headers.3529/

http://garage.grumpysperformance.com/index.php?threads/calculating-required-exhaust-pipe-size.11552/

http://garage.grumpysperformance.co...-guys-that-just-slap-on-factory-headers.3155/
reading these threads and sub links may help

http://garage.grumpysperformance.com/index.php?threads/calculating-header-design.185/

http://garage.grumpysperformance.com/index.php?threads/building-custom-headers.961/

http://garage.grumpysperformance.co...-between-shorty-and-full-length-headers.1303/

http://garage.grumpysperformance.com/index.php?threads/calculating-required-exhaust-pipe-size.11552/

http://garage.grumpysperformance.com/index.php?threads/calculating-header-design.185/


http://garage.grumpysperformance.com/index.php?threads/header-dimension-calculator.15013/


http://www.bgsoflex.com/auto.html

http://www.mk5cortinaestate.co.uk/calculator5.php

 

[brad.arcova]

OK, I'm still wading through all of these links and while it's great information about the ideal exhaust system it doesn't look like it's going to answer my question: how much is it going to help my engine efficiency (fuel mileage) to go from stock 1964 ram horn headers to either block hugger or shorty headers?

I have a brand new 383 that hasn't even been run yet that I want to make peak torque at ~3500 rpm and peak hp at ~5000 rpm. It has vortec heads and a cam with .487Int / .508 Exh & 234 Int / 244 Exh duration @ .050 - 110 degree lobe sep. The way I drive as a cruiser it looks like I've gobs of torque and power. I'll spend most of my time 1500-2500 and rarely go over 3500 rpm and never over 4500. I'll never even see the rated peak horsepower and I've intentionally put a smaller 670 cfm carb rather than the recommended 750 cfm carb. The calculators are showing that I should use no more than 1.75" exhaust pipes.

Of course the calculators are also showing that I should use long tube headers 42-60". The car is a '64 Impala with an X-frame and because of ground clearance issues getting around that weird frame, long tubes appear to be a non-starter. So, with more engine than I plan to use, is it going to help my fuel mileage significantly to go from stock cast-iron ram-horn manifolds to shorties or block-huggers? I can probably put in an H-pipe. Same question, is it worth the cost if my goal is fuel economy. I'm sure I'll have all the power I ever want no matter what I do. I plan to keep the car for about 30 more years.

Thanks!
Brad

 

[grumpyvette]

OK, I'm still wading through all of these links and while it's great information about the ideal exhaust system it doesn't look like it's going to answer my question: how much is it going to help my engine efficiency (fuel mileage) to go from stock 1964 ram horn headers to either block hugger or shorty headers?


the answer will depend mostly on how you intend to use the car, and the components you select to use with the headers, the cars engine design and factors like displacement, cam timing and how restrictive the exhaust past the collectors is to flow, below about 3000rpm theres usually not going to be a huge difference, simply because the restriction to flow and speed of the exhaust gases exiting won,t scavenge the cylinders a great deal more with headers, between about 3000-6500rpm the long tube headers should easily add 10-15 hp OR MORE, than the shorty headers in most cars

I have a brand new 383 that hasn't even been run yet that I want to make peak torque at ~3500 rpm and peak hp at ~5000 rpm. It has vortec heads and a cam with .487Int / .508 Exh & 234 Int / 244 Exh duration @ .050 - 110 degree lobe sep. The way I drive as a cruiser it looks like I've gobs of torque and power. I'll spend most of my time 1500-2500 and rarely go over 3500 rpm and never over 4500. I'll never even see the rated peak horsepower and I've intentionally put a smaller 670 cfm carb rather than the recommended 750 cfm carb. The calculators are showing that I should use no more than 1.75" exhaust pipes.

Of course the calculators are also showing that I should use long tube headers 42-60". The car is a '64 Impala with an X-frame and because of ground clearance issues getting around that weird frame, long tubes appear to be a non-starter. So, with more engine than I plan to use, is it going to help my fuel mileage significantly to go from stock cast-iron ram-horn manifolds to shorties or block-huggers? I can probably put in an H-pipe. Same question, is it worth the cost if my goal is fuel economy. I'm sure I'll have all the power I ever want no matter what I do.

Thanks!
Brad

at low engine rpms the exhaust PIPES, act as extended header collectors, on shorty headers and theres not a great deal gained below about 3000rpm(mostly because commercial headers rarely have the primaries near the correct lengths)

"Even if you're running a radical cam and a blower, you're better off sizing your headers smaller ... unless you plan to spend most of your driving at full throttle."

It is no secret that a good set of headers is one of the best performance investments. In fact, most engine builders say that headers are one of the first things you should upgrade to when modifying your engine. But before you plunk down your hard-earned cash, remember a couple factors determine what will work best for your particular application.

The first thing to consider is the intended use of your vehicle. Are you building a daily driver, a sometimes bracket racer, or a dedicated quarter-miler? The RPM range where you want the most torque, along with the displacement (size) of the engine plus any other serious modifications and power-adders (camshaft, blower/supercharger, cylinder heads, nitrous, etc.) are equally important factors.

Stock manifolds are mass produced and designed to clear all the accessories offered for any vehicle the engine block may go into. So naturally, factory exhaust system performance is compromised by manufacturing requirements. Tubular headers are built for improved flow, torque, and power---and their design can be very specific.

Let's look at how headers work, and clear up a couple common misconceptions. First is the size of the primary tube. It is easy to assume the bigger the primary tube the better, but that's not the case.

The fact is, primary tubes that are too large actually cost you torque and horsepower by slowing down the rate at which the exhaust gases travel through the system. Think of your engine as an air pump. Every time the exhaust leaves the combustion chamber it is being forced into the primary tube for that cylinder.

Smaller diameter pipes flow less volume than larger ones, but the exhaust in the smaller pipe flows faster. Until you reach the RPM where the sheer volume of exhaust gases require bigger primary tube diameters, smaller tubes will scavenge the cylinders more efficiently. If you are using the engine in the 1,500 to 3,500 RPM range, which is typical for a street-driven vehicle, you definitely want 1-1/2" to 1-5/8" primary tubes for any small block and 1-3/4" to 1-7/8" for a big block engine. Any bigger and you will lose a considerable amount of low end torque. beyond 3,500 RPM it is a question of where you want the power peaks. As you can see from the charts on this page, small tube headers do not lose their edge in horsepower and torque until you exceed 5,500 RPM.

Even if you're running a radical camshaft and blower, you're better off sizing your headers smaller rather than larger, unless you plan to spend most of your driving at full throttle. We size our headers correctly for even the most heavily modified street motors.

The second biggest controversy in header design is the "equal length" versus "shorty" styles---which is best? Like most performance products, there are advantages and disadvantages to both.

Exhaust headers with equal length primary tubes have been shown to develop slightly more power on an open exhaust system, but not when hooked up to a street system with mufflers. The fact is, most street motors with shorty headers will produce the same power as they would with expensive equal length headers.

Equal length tubes can produce more power, true. However, they must be the right length for the specific motor at the RPM range where you want the power. What that means is lots of custom fabrication and dyno testing, which translates into lots of time and money.

For racing applications, the slight gain may justify the cost, but competition cars are more easily built "around the engine" than street cars. When you are working within the confines of a given body style and chassis, with motor mounts, starter, steering linkage and accessories to think about, the way the headers fit becomes more important.

That is where the compact or "shorty" style header shines. You get a significant performance increase compared to stock exhaust manifolds, at an off-the-shelf price. Plus, Sanderson headers provide excellent clearance around spark plugs, starter and chassis components, as well as ground clearance for lowered vehicles. The charts on this page illustrate just how little power you trade off for the much lower cost and easy installation of compact headers.

We build hundreds of custom fabricated headers for one-of-a-kind cars, but for most vehicles you can get the performance you need with a set of Sanderson's right from our extensive product line.

Our headers are designed to fit right and to produce the power you expect. Plus, the use of top quality materials, construction, and patented flange design give you lasting value down the road. Hook 'em up to a well engineered exhaust system and you'll feel the difference.

Source of Chart Data:
Our Thanks to Chevy Action! Magazine

Test Engine:

• 433 cu. in. big block Chevy
• 10.4:1 compression
• Holley 780cfm carburetor
• Oval-port heads with 2.09" intake valves, and 1.88" exhaust valves
• High performance mechanical camshaft, specs 250°/259° duration at 0.050 lift

for those guys doing LS engine swaps, theres a whole bunch of different shorty headers
heres just a few of many

 

[grumpyvette]

JUST a bit of info,
one of the guys I know recently had his corvette dyno checked at a local track day, he was very disappointed , on his base run,to find out the engine he thought was making 450hp," like the magazine article he tried to duplicate during its build up," was really only making 297hp, , he was amazed, when I did a few tests and found his CATALYTIC converter was partly clogged , resulting in 5-6 psi of back pressure, in the exhaust over 5000rpm and his valves needed adjustment, and his fuel pressure was at only 3.5 PSI, once he hit about 4500rpm.
just correcting those problems got his second run up over 356hp

read these links

http://www.racingbeat.com/2001header/headertest.htm

http://www.mustang50magazine.com/techar ... index.html

http://www.circletrack.com/enginetech/c ... index.html

http://www.hotrod.com/techarticles/engi ... index.html

http://garage.grumpysperformance.co...ers-and-yeah-thinking-it-through-helps.15137/

 

[grumpyvette]

isky cams tech section had these related bits of info

Intake Restriction and Over Scavenging: "Waste not...Want not!"

It is certainly an over simplification to make the statement "that which is not wasted, should be inducted". However, in the case of restricted intake systems and in particular 2-BBL carb rules, it is not far off the mark. Engines with such restrictions are "choked off" to the point where they will not run much past 6500 RPM (if even that high) without dropping off sharply in power. You might have trouble running very fast yourself if someone had your windpipe choked down to say 50 or 60% of it's normal capacity. Under such conditions, would you volunteer to give blood at the Red Cross? Of course not, but without knowing so, racers often do the equivalent with their engines by running a camshaft better suited for a 4-BBL class! How So?

If you'll recall in last months tech tip: "Longer Exhaust Duration: Is This Really Necessary?" I discussed how, through habit, many racers and cam grinders alike are predisposed to running camshafts with longer exhaust durations, whether they need to or not! Well, in the case of restricted intake applications, if there was ever a situation in which you'd want to avoid the longer exhaust "trap" it's here! Especially the 8, 10, 12 or even longer degree spreads, I often discover people employing.

Use such a cam at you own risk - and don't be surprised to find that your exhaust temperatures are unusually high. Your headers in fact may even glow cherry red. There is a very good reason for this. Raw (unburned) fuel is burning "late" or in the pipe (header/manifold). You may have a good equilibrium of flow going here but there is just one problem. Much of what should be inducted into the cylinder is being scavenged out the exhaust! You see, although back pressure in an exhaust system can be restrictive, the only thing that could be even worse is a reduction of it to the point where you are now, in effect pulling a vacuum. In the case of an intake restriction, very slight back pressure is preferable to avoid "over scavenging".

Yes, Yes I know. You are probably thinking "what's wrong with a little scavenging?". Well, nothing if you can afford it. But with intake restrictions (either small 2-BBL carbs and/or restrictor plates) you must be very careful. You already have reduced intake potential and therefore simply cannot be cavalier about valve overlap and scavenging or you'll be way down on power and have those nice bright cherry red pipes to show for it! Case in Point: One racer who called me was in this exact situation and was running, not surprisingly, a 14 Degree longer exhaust duration. It was Friday afternoon and he needed a cam the next day for the last "points race" of the season and UPS had already picked up at Isky. "Too Bad" I said, "You don't have a set of those low ratio break-in rocker arms because they could really help in this case". " I do have some" he said "but they are only 1.2:1 ratio - is that okay?" I told him to use them (on his exhaust valves only of course) and he finished the race 2nd having come from the back of the pack. Later we made him the right cam so he could avoid this make shift approach.

Unfortunately, the symptoms are not always as obvious as in this case to allow for a speedy diagnosis. Also, it's not only longer exhaust duration that causes the problem. Although it is usually the primary offender, it is often coupled with too close a lobe separation angle of say 104 Degrees. A widening to 106 Degrees or preferably 108 Degrees (some go even wider) is usually prudent.

I am not absolutely dead set against a slightly longer exhaust duration in these cases as a 2-4 Degree longer exhaust lobe is permissible under some circumstances (if your running a completely stock exhaust system including mufflers for example). Each case is different, depending upon the equipment employed. I might even recommend shorter exhaust duration to some; if I feel they have "overdone" their exhaust ports and or exhaust system a bit. What matters is the end result and if you're out of balance on one side simply employ what I call the "Great Law of Compensation" to bring you back to that equilibrium of flow.

So, how can you tell if you may need to make some of these changes in your camshaft? Well, short of trying a lower exhaust rocker arm ratio, you can increase exhaust valve lash .004" - .008" temporarily to see if there is any improvement. You can also try and increase restriction (smaller headers or pipes, or in the case of open headers a longer collector) and simply observe the results. Remember, "One test is worth a thousand expert opinions". Keep this old axiom in your "tool box" and you'll be ahead of the game. How do you think Smokey's shop got to be "The best Damn Garage in Town" anyway? Yes, he had those country smarts, but his experiences in racing and his willingness to test are legendary!



Longer Exhaust Duration: Is this really necessary?

Most stock camshafts from American production V8, V6 and 4 cylinder engines manufactured today are ground with the longer exhaust lobe duration. Or, another way of looking at this is that they are ground with shorter intake durations! The former embraces the viewpoint that either the Exhaust Ports or Exhaust Pipe system is somewhat restrictive, and is in need of an assist. The latter suggests that the intake system is rather efficient and cam timing can be trimmed back a bit with out much sacrifice in power, in order to maximize throttle response and cruising efficiency.

Take your pick here. There is no absolutely correct viewpoint - because both are probably true! In a stock engine running at conservative RPM levels, for the sake of overall efficiency, fuel economy and a quiet smooth running engine, this staggering of intake and exhaust duration is quite common and appropriate.

However, High Performance is another thing entirely. Change one factor, let's say in this case, the exhaust system (installing headers and larger pipes) and you have just negated in most cases, the need for that longer exhaust lobe. Now couple this change with a different intake system and camshaft and you have really scrambled the equation. But, wait just a moment. Why is it that so many people (racers & cam grinders alike) insist on running a cam with longer exhaust duration regardless of what equipment is employed? The answer is "habit". Most of them have been somewhat successful in doing it their way and will probably never change unless virtually forced by circumstances to do so.

Before we go any further however let's review what it actually is we are trying to do with an engine when we attempt to make more power. Our best result comes when we are cognizant of the fact that an engine is basically an air pump. We pump it in and out (although in a different form) and we have problems when one side or the other is restricted. Balance or the equilibrium or flow should be our objective, unless of course we are not trying to make more horsepower!

Example #1 (Oval track racing) Here, I have often observed that the most experienced drivers are those who are most likely to run a single pattern (equal on intake and exhaust duration) cam. Why? Because such cams always, I repeat always make more torque! These veterans have a more educated foot and greater experience in feathering the throttle in the corners. They can therefore, utilize the benefit of added torque, in the lower to mid RPM range, to their advantage.

Their counterparts, the younger drivers on the circuit, generally are not as experienced and may at times actually get "crossed up" in the corners especially with a lighter car or when they are learning the ropes. In their case, a longer exhaust duration is often the more appropriate choice. It will often help them to drive better, more "flat footed" if you will, without consequence. But please for the sake of accuracy, let us be truthful. The benefit comes from an actual bleeding off of low to mid range torque, which is always what happens when Exh. Duration is lengthened, not from any improvement. The improvement, (if any) would come because of an improvement in scavenging at the extreme upper end of the power curve and would usually be marginal at best. Yet the so-called "extra power" potential of a longer Exh. Duration cam is most often why they are touted - power most people are backing away from at the end of the strait away!

Example #2 (Drag Racing) At the drag strip it's a little different and I feel more honest. Here, racers have long enjoyed longer exhaust and longer durations across the board (If I may add specifically for the purpose of "killing" low-end torque) to keep the tires from too easily breaking lose. This has been successful and sometimes actually results in a slight increase in top end power - something you can actually use in drag racing since it is a full throttle endeavor through the lights. Keep in mind here though, it's quite possible that a longer duration cam overall would have done just as well or better. In other words if you needed that longer exhaust for top end, perhaps the intake could have benefited from such a lengthening as well.

One of my favorite expressions is how "The Drag Racing mentality has infiltrated the ranks of Oval Track". Many have crossed over and made the switch in the past 10-15 years and some have brought their preconceived notions about how to cam an engine with them. A few may actually read these concepts and if they do so will at least come away with a better understanding of what they are doing. On the other hand they also could find that this information might actually help their cars to run just a bit faster!

Note: Readers may find Camfather Ed Iskenderian's Top Tuners Tip #33 "Can an Exhaust System Over-Scavenge the Combustion Chambers" to be a relevant precursor.

What Causes Intake Reversion? Once and for all, let us have the TRUTH!

With the proliferation of the Motorsports Industry over the years, many new faces have come on the scene. In the cam grinding business today, there are many younger, less experienced companies struggling for recognition of their talents and a few have turned to postulating new theories in order to attract attention. However, they are I believe unfortunately, too often guilty of shooting from the hip.

Two in particular are responsible for perpetuating the "myth" that an earlier opening of the intake valve (even by a mere 2 or 3 degrees) causes the phenomenon known as "reversion". Nothing could be further from the truth! This misconception not only defies common sense, it also establishes a false premise from which other, incorrect conclusions can be drawn. Simply put, those who focus on overlap are on the wrong end of the cam-timing diagram!

Reversion, carburetor/Injector "stand-off" or the general effect of the backing up of the intake Fuel/Air charge normally associated with longer duration high-performance camshafts is actually caused by a Later Intake Closing! How do we know this to be true? The answer lies in the basic principles of physics. For as with geometry and trigonometry, these sacred truths do not change simply because someone chooses to ignore them in an attempt to garner a reputation.

Specifically, when the intake valve opens some 40 or more degrees before T.D.C. at the end of the exhaust stroke, very little (virtually no) exhaust gases remain in the cylinder. The piston is in the vicinity of T.D.C. (only .425" down the hole @40o BTDC - on a typical 350" Chevy with 5.700" rods) and no appreciable threat is posed to the forthcoming intake charge. The "False Reversion Hypothesis" taken to an extreme would lead one to the equally false conclusion that any overlapping of the intake and exhaust valves is totally undesirable. Automotive engineers of the late 1800's and early 1900's used to think this way. They were deathly afraid of overlap, so much so they actually employed "Negative" overlap (minus 5 or 10 degrees) to be absolutely sure none would occur. What was the result? These engines were severely "throttled back" or limited to low speeds and mediocre output. [ Reference: Iskenderian's Tech Article "Cam Degreeing is Simple"] But, more progressive engineers of the early 1920's who performed "brazen experiments" with longer duration cams proved these overlap fears to be only so much "stuff and nonsense", as both power, rpm and performance were actually improved. These engineers demonstrated that overlap did not cause engines to quiver, backfire or lock-up on the spot! Although, the ignorance displayed by their predecessors is easily explained by their lack of experience, (internal combustion engine design being in it's infancy) it was none the less the result of an incorrect hypothesis.

Should you need further persuasion that reversion is not caused by earlier intake opening and the resulting extension of valve overlap, consider this: What happens when you advance any camshaft? The intake as well as the exhaust valves open earlier. Does this advancing of the cam cause more reversion? Of course not. Throttle response and torque are enhanced. Yet, if these theories were correct wouldn't the engine run more poorly, especially at lower RPM? The answer is obviously yes, and because so, these theories are invalid. A brief look at what's happening on the other end of the valve-timing diagram will tell you why.

For when a camshaft is advanced, not only do both valves open earlier but they of course also close earlier - and here in lies the key to reducing Intake Reversion. Close your intake valves earlier and any tendency for the occurrence of Reversion or the backing up of the intake charge as the piston rises on the compression stroke will be reduced. It's not complex, nor is it a mystery. And the circumstances surrounding it's occurrence have not changed. In fact any experienced mechanic could tell you as much, for, as Ed's good friend the legendary Smokey Yunick might say, "Only country smarts are required to solve the problem."

 

[grumpyvette]

these pictures are from the engine master challenge, where making max hp is the goal!
these guys are competing for big buck$ and do everything they can to increase hp under strict rules!
and a correctly configured header with LONG tubes and a well designed collector can go a long way to making the extra hp they depend on to win,
NOTICE THE LONGER HEADER DESIGN THAN MOST FACTORY HEADERS

 

[Indycars]

Big difference in the length of the primaries, between those two engines. I've never seen primaries that long in the bottom picture. Bet they would be a bear to install.

 

[grumpyvette]

the point I was trying to make obvious is that many, even most commercial headers are designed mostly for ease of installation, minimal material use. and ease of manufacture, rather than ideal power production.
while few guys seem to realize it, and just buy what ever header, is listed in a catalog,that fits the car in their budget, the truth is that most headers designed can be significantly improved if you want to take the time to do the calculations and then match it with the modifications to commercial headers OR by building custom headers, and in many cases its not that difficult to do so.

in many cases fairly cheap headers like these can have the collectors cut off and have these longer collectors below added and the mods worth a good deal more in low rpm, and in mid rpm torque
yes it takes some time and a welder, but you can normally get almost the results of $1000 custom headers using the collectors and cheaper commercial headers as components easily saving several hundred dollars or more even if you get the modified headers ceramic coated

http://www.summitracing.com/parts/FLO-C ... /?rtype=10



YES AS USUAL THERES A TON OF VALID USEFUL INFO IN THE RELATED THREADS AND LINKS

viewtopic.php?f=56&t=961

viewtopic.php?f=56&t=3155

viewtopic.php?f=56&t=185

viewtopic.php?f=56&t=1247&p=2668&hilit=thermal+coating#p2668

http://www.qccoatings.com/

viewtopic.php?f=56&t=495

viewtopic.php?f=56&t=1166

viewtopic.php?f=56&t=255

viewtopic.php?f=56&t=352

 

[grumpyvette]

hey grumpy? if I swap from my rams horn exhaust manifolds to a decent set of headers , how much extra power am I likely to see from the exhaust upgrade"


this is a common question and the answers not always a fast and sure power level increase.
your results will change dependent on factors like with changes in your engine compression, displacement, intake flow rates ,cam timing, exhaust back pressure, etc.
long tubes with a low restriction exhaust behind them and matched to the correct combo an easily give you an additional 20-30hp over shorty exhaust headers, or a rams horn manifold, but thats not average or even likely on most cars with a stock restrictive exhaust, yet its easily done on cars with an (X) pipe and a low restriction exhaust system, and it changes a good deal with header design and the operational rpm.
THERE'S A TON OF RELATED INFO

 

[grumpyvette]

http://www.pfadtracing.com/catalog/prod ... cts_id/278
heres a fairly new company building headers

http://forums.corvetteforum.com/1582143073-post1.html

http://www.pfadtracing.com/blog/?p=498

 

[grumpyvette]

http://www.powerblocktv.com/episodes/HP ... mance-mods

you might find this interesting

AND for anyone who thinks headers are not an important component in your engines efficiency ,heres a rather interesting dyno test where carefully ported rams horn type exhaust manifolds were tested against a set of 1 3/4" headers, the result with this particular engine combo was that the engine made just over 500 hp with headers but LOST 95 hp once the cast exhaust manifolds were installed replacing the headers


I've always preferred the side exhaust header /muffler design on the C3 corvettes,and A.C. COBRAS,

,(like these picture's shows them) my B.I.L well remembers my 1968 BBC corvette so he has installed those hooker side pipes on his 1974 BBC corvette

and on my 1968 corvette the car was slower by almost 2 tenths with the standard comp plus hooker under frame headers,
( I tried them because they potentially saved weight,
(obviously that was with the internal muffler inserts removed from the side pipes while racing)
but the under the car mufflers added too under the car headers total, weight,
are HEAVIER than the side pipes when the whole exhaust system is installed
if you do the required math calculations , you,ll find that most commercial headers are using primary tube length that are too short to be ideal,
as this simplifies manufacture and CLEARANCE ISSUES AND REDUCES MANUFACTURING COSTS.
(the headers with side exhaust design, are closer too the ideal)

related info

http://garage.grumpysperformance.com/index.php?threads/calculating-header-design.185/

http://garage.grumpysperformance.com/index.php?threads/calculating-required-exhaust-pipe-size.11552/
http://www.yenko.net/ubbthreads/ubbthre ... /415017/16

THERE IT IS!!! 504 HP @ 7400 rpm! That was my goal with headers, and once I realized we were off quite a bit on the camshaft I was pretty doubtful we would see it. Again, keep in mind the cam in this engine as supposed to be designed to run with ported exhaust manifolds, and was to have a "stock" idle. The idle went out the window as soon as the engine fired for the first time, and w/o giving away any camshaft details, the LSA on this cam has been a concern to me since I received it, but I was placing my trust in someone else's expertise. It's not a big issue, I didn't expect them to hit a bulls-eye the first time around, that's all part of the deal when building engines like this.

Now that we'd hit my power goal with the headers, it was time to try the manifolds.

As much as it pains me to say this, as I feared once I realized the cam wasn't right, the manifold test was a bust. The engine flat-out HATED the manifolds...it lost 95 horsepower with the manifolds installed. eek However, even though the engine was obviously unhappy with the manifolds, peak power still came in @ 7200 rpm. As such, that will have to be re-tested during the next round of testing.

504 HP from 306" is just under 1.68 HP/CI, and 397 lb.ft of torque is 1.29 lb/CI. That's pretty stout considering how much there is still left on the table with this build.

Last comments regarding the dyno sheets: This time the air/fuel ratios are correct, but the VE figures are nowhere close. I calculated VE using Pipemax software and it showed roughly 94% VE to match the actual dyno numbers.

So that's it for now on this build, but rest assured, there will be more to come! Along those lines, I'd like to hear what you would like to see me do with this engine project--stick with the "F.A.S.T." theme?...go balls-out with headers?...tame it down a little with a more "practical" set of heads and cam?

 

[Grumpy]

http://www.airflowresearch.com/hot-rod-nov-2013-305cc-bbc.php

Bolting on a set of headers has long been one of the first moves a hot rodder makes in search of more performance. Traditionally, factory iron log exhaust manifolds are set aside in favor of a pair of tube headers, typically of the four-into-one configuration. Most enthusiasts know that the headers will provide an increase in power, generally attributing the gain to a reduction in backpressure. Sure, reduced backpressure is a factor, but the real secret to a set of headers is the tune, determined by the length and diameter of the primary tubes and collector.

At each combustion event a pulse of high-velocity exhaust gas makes its way down the primary tube, and upon reaching the collector at the end of the primary tube, a low-pressure wave is reflected back up the pipe. Now if that low-pressure wave reaches the exhaust valve while it is open during the overlap period, the pressure differential will actually scavenge the cylinder of exhaust gases. Since the intake valve is also open during overlap, the effect is to actually draw on the induction side. This scavenging effect actually aids in filling the cylinders with a greater charge for higher volumetric efficiency and, of course, more power. The cam plays a vital role here, since the overlap provides the window for the scavenging effect to occur. Obviously, a very short duration cam with virtually no overlap will represent a closed door to the exhaust header scavenging. Fortunately, most hot rodded engines are also equipped with bigger cams, which go hand in hand with headers.

Often the final header configuration is more a matter of what is available and what will fit the car than a result of number crunching theory. In the real world, cataloged header configurations are what most guys have to choose from, and the usual compromise is the bigger the header gets, the harder they are going to be to install and the more intrusive they become in the engine bay. The key piece of information that is usually missing is just how much of a difference in performance is gained or lost with a given header choice. If a 17⁄8-inch header will put you within a few odd horsepower of a 21⁄8-inch header, most guys would see the smaller header as the sensible choice. If on the other hand, there is 10, 20, 30, or even more horsepower dependent upon stepping up the header size, at some point it is going to be worth the effort to get the bigger pipes under the hood.

To get a handle on the variations in power output with a typical high-output street engine, we gathered a wide range of popular big-block Chevy headers from Hooker. Represented were 13⁄4-, 17⁄8-, 2.00-, and 21⁄8-inch full length headers, all with Hooker's factory silver ceramic metallic coating. To judge the effect of the header coating, we also had on hand a set of plain black painted 17⁄8-inch headers identical to the coated version for a back-to-back test. We completed the lineup with a set of Hooker Block Hugger shorty headers, also in a 17⁄8-inch primary tube diameter. Our test engine is a high-performance street big-block Chevy based upon a stock stroke 427. The engine was built with just under 10:1 compression, a pair of AFR 305 "as-cast" cylinder heads, a Crane 246/254 duration-at-.050-inch Street Roller cam, an Edelbrock Victor single-plane intake, and a Holley 950-cfm Ultra HP 4150 carb. Here is how the various pipes stacked up.

As the numbers show, there was quite a lot of power to separate the various header configurations, with as much as a 39hp spread in peak-to-peak horsepower, between the shorty header and the best performing long-tube, the 2.00-inch. The shorty header certainly did not provide the same exhaust tuning and scavenging effect of any of the long-tube headers, with a significant loss in torque and power throughout the curve. Our smallest full-length header, the 13⁄4-primary pipes produced substantially more power throughout the rpm range, and a particular advantage in torque in the 3,500-4,000 rpm range. For all-out power, the long-tubes win, but in many installations the shorty headers are a much easier fit.

Getting into the various full-length headers, bolting on the 17⁄8-inch headers brought into focus the shortcomings of the smaller headers. The larger pipes showed a healthy increase in top end power of 21 peak horsepower, while even managing a torque advantage right from the bottom of our test range of 3,000 rpm. The smaller pipes had a short-lived advantage in the 4,000-rpm range, but the average power gives the nod to the larger pipes. Stepping up another level to the 2-inch headers showed another gain in top end power, this time a more modest increase of 11 hp at the top of the power curve. At the lower rpm levels, these two headers swapped the torque advantage depending upon the engine speed. Moving to our largest header, the 21⁄8-inch primary, we seemed to be reaching the point of diminishing returns. As with our previous test, these headers swapped for torque advantage through the lower rpm range, while at the top end the larger tubes were actually slightly down on peak power. Overall, the big pipes were an overkill, sacrificing fit and packaging for no real gain.

Coatings: Are They Worth It?
As a part of our test, we wanted to quantify the benefits of a coated header versus a plain uncoated black painted header. A thermal barrier ceramic coating adds considerably to the price of any header, often doubling the price. We tested two otherwise identical Hooker 17⁄8-inch headers with surprising results. Running on the dyno, we found the power numbers virtually unchanged (see Average Power table on next page). Where the ceramic coating made a remarkable difference is in the heat transferred by the header. We tested the header temperature immediately after a run, and then one minute after shutdown. The coated headers measured 258 degrees F dropping to 195 degrees F a minute after shutdown. In contrast, the uncoated header measured a scalding 870 degrees, retaining 520 degrees a minute after shutdown. We didn't need a heat gun to tell the difference in the test cell.

Our next test loaded the engine to 60 lb-ft of torque at 2,800 rpm, simulating a high-speed cruise situation. We gauged the surface temp of the header once fully stabilized. Once again, the difference was huge, with the coated header showing 288 degrees, while the uncoated header recorded 850 degrees. While the dyno run didn't show much difference in output, an engine breathing air from under the hood will definitely feel the effects of that extra 562 degrees F pumping into the engine bay. Taking account the effects of heat on engine component life and passenger comfort, the coated headers are definitely a winner.

Collector Extensions: What Do They Do
For years we have been told of the value of collector extensions when running open headers. No serious drag race car would be running without them. It was simple enough to quantify the benefit of collector extensions while on the dyno, so we ran the 17⁄8-inch headers with and without an 18-inch collector extension to have a look. Those old drag racer tales certainly held up, with the extensions producing a tremendous boost in torque. In the 3,000- to 4,000-rpm range, there was more than 50 lb-ft of torque added by the collector extensions. The extensions add to the secondary tuned length of the header, adding heavily to torque at an rpm range that counts. If your plans are to uncork the exhaust at the track, it is definitely worth packing a set of collector extensions.
AVERAGE POWER
Test RPM range Avg. HP Avg. TQ
Shorty 17⁄8-inch 3,000-6,700 446.1 482.9
13⁄4-inch coated 3,000-6,700 456.7 495.8
17⁄8-inch coated 3,000-6,700 466.6 505.0
17⁄8-inch uncoated 3,000-6,700 465.8 504.4
2.00-inch coated 3,000-6,700 467.7 505.3
21⁄8-inch coated 3,000-6,700 465.7 503.6
17⁄8-inch no extension 2,500-5,000 340.4 469.9
17⁄8 18-inch extension 2,500-5,000 354.8 490.6

 

[87vette81big]

I have pictures I took of the 1995 Cobra Mustang 4.6 LV8 DOHC Long Tube Header install I did at work Grumpy.
BBK Long Tubes with a Matching X Pipe BBK.
Fitment was very good.
PIA To install.
Job took about 12 hours.
I removed the K -frame. Front coil springs had to be removed 1st.
Transfer pictures from my phone to photobucket and to here.
Get it done by morning.

 

[chromebumpers]

I read a couple of times on another forum that the long tube Hooker headers with side pipes that are on my '71 are killing horsepower. Is this true? I don't know if it has a performance cam or not but everything else is stock 350 4spd.

 

[87vette81big]

I read a couple of times on another forum that the long tube Hooker headers with side pipes that are on my '71 are killing horsepower. Is this true? I don't know if it has a performance cam or not but everything else is stock 350 4spd.

Its the Hooker Muffler inserts that knock down HP.
Grumpy had pictures of homemade muffler sidepipe inserts that help retain HP.

 

[chromebumpers]

When the cooler weather comes I'll get working again on the 71, I wish I had a buyer right now.
There's not one vette for sale in CList in the Philly area, I never witnessed that before.

 

[Grumpy]

most people have the wild mis-conception that simply adding headers will some how boost power, headers are used to increase cylinder scavenging efficiency, thus increase the engines ability to efficiently burn the fuel/air mix that produces the cylinder pressure that drives the pistons ,that allow the engine to build torque or its ability to spin the engine against resistance , allowing it to move the car, and that only works if the exhaust system attached beyond the header collectors has a very low exhaust flow restriction in the engines intended operational range.
an increase in exhaust back pressure , results in a reduction in scavenging efficiency

refer
http://www.veryuseful.com/mustang/tech/engine/exhaustScavenging.pdf

http://www.epi-eng.com/piston_engine_technology/exhaust_system_technology.htm

http://garage.grumpysperformance.com/index.php?threads/is-backpressure-hurting-your-combo.495/

http://garage.grumpysperformance.com/index.php?threads/building-an-exhaust-system-for-your-car.1166/

http://garage.grumpysperformance.co...ion-on-the-exhaust-on-some-cams.506/#post-626

http://garage.grumpysperformance.com/index.php?threads/basics-on-exhaust.45/#post-2026

 

[Grumpy]

we all know guys who purchased a set of headers, that did not fit correctly!
(yes its usually the less expensive generic brands that don,t clear and fit correctly)
, and the process they used too get the required clearance ,getting the headers to fit the car frame & suspension,was less than gentle, they used, mostly a ball peen hammer ,
and an
" I JUST don,t give a crap attitude!
followed by the statement that, "
a couple dents won,t hurt a damn thing! "
well watch this

UNDENTED

RATHER EXTENSIVELY DENTED TO THE POINT YOU WOULD EASILY ASSUME THEY ARE DRASTICALLY HURTING POWER

while Ive repeatedly seen, dyno tests where a restrictive exhaust or a partly clogged catalytic converter ,
or restrictive mufflers connected behind the header collectors,
cut power 40-80 hp, a few rather impressive dents on a set of headers has a good deal less effect,
than you might think,
, AS LONG AS THE EXHAUST SYSTEM MOUNTED BEHIND THE HEADERS
IS NOT RESTRICTING EXHAUST GAS FLOW, ITS BACK-PRESSURE NOT DENTS (WITHIN REASONABLE LIMITS) that KILLS POWER

 

[Indycars]

Well that was enlightening to say the least!

 

[Grumpy]

after watching that video it would be very easy to erroneously conclude that the choice of headers and exhaust system you stick behind those headers on your engine is really not of much concern, but theres a huge difference between denting a few header primary tubes, that reduces the cross sectional area reducing flow slightly and having an exhaust thats restrictive enough to build significant back pressure beyond the collectors.remember the exhaust valve opens with well over a 100 psi of pressurized exhaust gasses being forced out in fractions of a second , but each primary exhaust pipe sees intermittent pulses , with pressure waves

most people have noticed that the exhaust valve size tends to be smaller than the intake valve size, and the reason is the intake side of the engine operates at far lower pressures.

as the intake valve opens and the piston drops away from TDC,the outside air in the intake runners tries to rush in to fill the lower pressure area over the piston, but its the effective inertial scavenging that the fast exiting exhaust gasses provide, which if properly designed, provide 4 to 5 times the suction to the intake port , during the valve overlap period compared to the piston alone that enhances cylinder fill rates,

and that effect is virtually eliminated if the back pressure gets over about 5-6 psi .
remember exhaust gasses exit the exhaust port at well over 100 psi, while the intake has ambient outside air pressure , usually less than 14.7 psi at sea level to induce air flow, so the inertia of the exiting exhaust gases play an effective roll in dragging in the next intake charge if the cam timing and headers design allow scavenging to function correctly.