IM ALWAYS AMAZED AT GUYS THAT JUST SLAP ON factory HEADERS

grumpyvette

Administrator
Staff member
ok you want you car to perform well and you've heard all your adult life, that you need a low restriction exhaust and that a good set of long tube headers out performs shorty's, headers,
you might have researched a bit deeper and found formulas that indicate the ideal length of the collectors and header primary, you might even be the one guy out of 20 that actually took the time and effort to run a flexible tape measure thru each primary and out the collector and found that about 90% of the factory headers use pipes and collectors that are far too short to produce the ideal power range, now what?
AND be aware that there's strait and angle plug, SBC heads and BIG BLOCK HEADS with raised exhaust ports ,and there's round and square exhaust ports, and its smart to check with the manufacturer as to what style heads the headers are designed too fit correctly or you could have major clearance issues.
ITS extremely important that you ask questions and get accurate answers , BEFORE purchasing headers about what style cylinder heads the headers are designed to fit, below is pictured a set of headers obviously designed for factory strait plug heads but bolted to a set of angle plug heads making spark plug access and wiring a clearance and heat , destroying ignition wire nightmare

ITS extremely important that you ask questions and get accurate answers , BEFORE purchasing headers about what style cylinder heads the headers are designed to fit, below is pictured a set of headers obviously designed for factory strait plug heads but bolted to a set of angle plug heads making spark plug access and wiring a clearance and heat , destroying ignition wire nightmare
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angle plug
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http://forum.grumpysperformance.com/viewtopic.php?f=52&t=2712&p=7032&hilit=angle+plug#p7032

http://forum.grumpysperformance.com/viewtopic.php?f=70&t=840&p=9944&hilit=angle+plug#p9944


Once you get much past the headers, the pipe size has little to do with the power curve unless you're choking the exhaust at high rpm's.
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I have got to agree here,its been my experience on many muscle car engines that a large displacement ,high compression performance engine, thats been specifically camed and geared correctly to maximize the exhaust scavenging will be easier to demonstrate this with than a low compression, mid sized v6 or v8 thats camed to run in the 1500rpm-4000rpm band like most factory transportation type cars are. but the exhaust behind the headers will be less critical than the headers dimensions and collectors design and collector length which can be critical to getting the engine to produce good power over a wide rpm band, but past that you feed both collectors into a correctly size (X) pipe with about 20" on each leg past the (X)and as long as the exhaust system past that point is not restrictive sound levels may change but power tends to be fairly consistent. i usually get that DEER IN THE HEAD LIGHTS STARE when i ask what the exhaust back pressure actually reads with a GAUGE, at the collectors, (X) PIPE and about 12"past the (X) pipe, at peak rpms under load , simply because most guys have never hooked up a guage and watched it as the car ran thru the 1/4 mile lights at top speed
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you might be surprised at what a few tests show you and how much time and money you can avoid wasting.
diam. of the pipes is not as critical as the exhaust BACK PRESSURE the engine sees in the mid and upper rpm ranges, a 2.5" pipe has ABOUT 5 square inches of area a 3" pipe ,about 7 square inches of area so, if you swap from a set of 2.5" exhaust pipes to a 3" dual exhaust , in theory youve reduced the resistance to exhaust flow by 35%-40% which MAY result in some gains if you were previously restricted, adding an (X) pipe adds a further reduction in the restriction to exhaust flow.
knowing a few constants in engine pressure and flow helps, Im always amazed at how few guys bother to measure exhaust temps, exhaust back pressure and fuel/air ratios.
IF your thinking about building a kick butt race engine, I discussed some of the requirements for building a real race engine, late in this thread and its links
what youll rapidly come to realize is that an all out max effort engine will require about a 4500 feet per minute piston speed , a connecting rod as close to 1.9:1 length to stroke RATIO WITH A 6" CONNECTING ROD being preferred in the 302-327-350 SBC and the 6.385" rods preferred in the 427,454, and 496 BBC engines, and about 13:1 compression using higher octane race fuel and a solid lifter roller valve train in most cases, this obviously requires a matching drive train gearing and while you might make far better than average power per cubic inch in the 1.5 or greater horse power per cubic inch range you also build an engine thats not ideal as a daily driver or for decent fuel economy
for those guys doing LS engine swaps, theres a whole bunch of different shorty headers
heres just a few of many

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if you want max engine performance under predictable conditions,
it will take some testing, measuring and thought,:D

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

an engine usually requires approximately 2.257 cubic feet per minute per horsepower to maximize intake flow and exhaust flow at about 115 cfm per square inch

so assuming your building a 500 hp engine / 2 (divided by 2 as there's normally two header collectors on a v8) we have 250hp per header collector, (open header collectors) multiply that by 2.257 cfm and you see you need 565 cfm and divide that by 115/square inches and we see we need a 4.9 square inch minimum exhaust collector pipe, per side (open header collectors), or if using mufflers this of course assumes a very low restriction muffler.
its a rule of thumb or rough guide on the expected combined potential max exhaust port flow rates of the exhaust primarys, taken from an observed average of hundreds of recorded dyno results, and not taking into account any flow loss or restriction,and calculating some heat expansion ,its basically worthless except as a way to figuring what size exhaust pipe size thats likely to work, or what size will be restrictive to flow.
torquecurvespipe.gif

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watch video
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keep firmly in mind that the header exhaust scavenging ,efficiency and intake runners ability to effectively fill the engines cylinders is very much dependent on carefully matched, cam timing, headers designed to match the engines displacement, intended rpm band, ,maximum compression ratio, for the fuel octane used,and a low restriction exhaust behind the header collectors, when all the factors are well matched correctly theres an easy 20% or higher power gain over most stock engines in this area alone.
correctly matched headers, compression, cam timing, displacement etc, can easily increase the cylinder fill efficiency, and intake runner air flow velocity by over 30%
USE THE CALCULATORS to match port size to intended rpm levels... but keep in mind valve lift and port flow limitations
http://www.wallaceracing.com/runnertorquecalc.php
http://www.wallaceracing.com/ca-calc.php
http://www.wallaceracing.com/area-under-curve.php
http://www.wallaceracing.com/chokepoint.php
http://www.wallaceracing.com/header_length.php



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


http://www.wallaceracing.com/intake-runner-length.php

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


http://www.pontiacstreetperformance.com/psp/exhaust.html

http://www.velocity-of-sound.com/velocity_of_sound/calculator3.htm

http://www.velocity-of-sound.com/velocity_of_sound/velocity_stacks.htm

http://www.swartzracingmanifolds.com/tech/index.htm


http://www.jegs.com/p/Vibrant-Perfo...nless-Steel-Merge-Collectors/3170441/10002/-1

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

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
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http://www.harborfreight.com/fuel-pump- ... 93547.html
viewtopic.php?f=56&t=1503

viewtopic.php?f=56&t=185

viewtopic.php?f=56&t=1166

viewtopic.php?f=56&t=495


if you look closely youll see the major difference is how easily exhaust flow pulses can move into the adjacent pipe to balance flow, the (H) pipe requires two 90 degree turns while the (X) pipe can easily balance with only part of a pulse expanding as it passes the (X) PIPE) merge point, the ease in balancing pressure, and reducing restriction greatly favors the (X PIPE DESIGN)

installxpipe11.jpg

notice the X pipe design has several variations, the type above is more effective than the type below at blending and equalizing the pulse volume from either side but even the more restrictive version below still works well.
x1.jpg

heres a good example showing why an (X) pipe is very efficient at equalizing and blending exhaust pulse flow rates
viewtopic.php?f=56&t=1166

mock1.JPG

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well most header manufacturers will produce what they feel is a decent compromise between performance and ease of installation, while keeping their cost to manufacture as low as they can, and since a shorter headers easier to install and costs less to produce in materials, and its less likely to have clearance issues far more of the commercial headers are much shorter than the ideal length.almost all header manufacturers need and do find a compromise between building the best possible headers , with the widest potential power band,and the most cost effective design they can build that still functions reasonably well, and fits as many similar applications as possible, and while a longer header tends to produce more low and mid rpm power, the ratio of power gains are reasonably small compared to the added expense of building true custom headers that fit, each possible application, due to clearances, and additional materials, and producing a header that may only fit a single year , with a single engine or type of cylinder heads,or maybe only limited to several years of production, and the cost difference between lets say a 32" and a 36 " header primary design, limiting the market potential, makes producing headers with the ideal measurements cost prohibitive.
the the additional gains are there to be had, but unless your willing to build a custom design that may only fit a few cars, and are looking for every possible gain, it may not be worth the extra effort, if it costs you an additional $200-$300 dollars to build a header that produces an extra 10-15 ft lbs of torque ,(or in some cases noticeably more) most header manufacturers would much rather opt for a less expensive option

there ARE EXCEPTIONS
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grumpy, who makes a really good quality header for my car?


I get similar questions all the time, and there ARE certain brands that do have a reputation for better fit and finish on headers,
but your results are totally dependent on you doing accurate ,prior research, your asking the correct questions,
knowing exactly what cylinder heads your using,and yes better quality tends to cost more than bargain basement prices!
knowing exactly what car it will be installed into and if your dealing with a better quality manufacturer helps.
cylinder fill efficiency is a compromise, your engine design is forced to make selecting the way components are matched, the factors of cam timing compression and exhaust header tuning all must fall in the same 3000 rpm power band and ideally in the same 1500 rpm range to maximize power.
the choices between cam timing and compression ratio, and head and intake flow rates, valve size and valve lift and duration,
has a huge effect on,exhaust scavenging and while most people think the port flow rate is mostly the result of the piston dropping away from TDC,
lowering the cylinder pressure , thus drawing in the intake runner charge, this is not the major factor once the engine rpms increase significantly.
its exhaust scavenging during the valve over lap , being well matched to the engine displacement and cam timing, header diameter, and length, and collector design,
and intake ram tuning that can significantly boost cylinder fill and cylinder scavenging efficiency rates.
OK, first fact! the piston can,t compress anything being trapped in the cylinder by the piston compressing it as it raises,until both valves seat & seal

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http://garage.grumpysperformance.com/index.php?threads/calculate-compression.9162/#post-32706

http://garage.grumpysperformance.co...lsa-effects-your-compression-torque-dcr.1070/
http://www.superchevy.com/how-to/148-0404-best-headers-shootout/

http://www.lemonsheaders.com/

http://www.stahlheaders.com/

http://www.stainlessheaders.com/

http://stainlessworks.net/products/performance-systems/headers

http://www.burnsstainless.com/

https://www.carid.com/performance-headers.html
and some simple fabrication work to graft on collectors like these
flo-c158218234.jpg


to common headers like these
hok-2456-1hkr_w.jpg

usually results in gains in performance, at a reasonable cost to the few guys willing to take that extra effort



well the more advanced guys, and racers have found that that making longer headers out of short factory designs is far less work intensive than building headers from scratch, and its fairly quick process to correct, with longer collectors or primary pipe extensions like pictured below,
but that usually requires some minimal cutting and welding to produce a decent , semi custom header, so if you don,t have the skill or tools many guys avoid doing it!

yes its usually well worth the cost and time and effort, most guys who have never had a car with headers of the optomum length have never seen how effective true tuned headers can be or heard and felt the difference they make over the crappy store versions with the much shorter tubes
you can usually use a band saw or cross cut saw to cut of the usually pathetically short factory collectors and weld on an extension giving you noticeably more low and mid rpm torque, that the factory supplied version.
collectors, like those pictured below that transition from 4 primary too two secondary to one collector usually produce better mid and low rpm torque without sacrificing much if any peak hp over the 4 into one collectors, and the smooth merge collectors that are usually far less restrictive can sometimes provide very noticeable improvements in the upper rpm range.
naturally if you match any header to a restrictive exhaust, or use mufflers that restrict flow your effectively killing off a great deal of its potential, just as a restrictive intake system will restrict the headers ability to scavenge the cylinders or if your using a cam that's not designed to run in the same rpm band as the headers and intake are designed to flow efficiently in, so it pays to take the effort to measure back pressure and include an (X) pipe and low restriction mufflers if you do run an exhaust system, and match all the engine components to a single intended power band, and, Id point out that having cut outs to further reduce restriction for on track use can at times help.


use these calculators and measure your current headers and youll find that about 90% of the time they are far to short to provide the ideal power curve
keep in mind the idea behind running headers is to significantly increase cylinder scavenging increasing the width of your power band by increasing the rpm range the cylinders fill efficiently



volumetricefficency.gif


if your headers primary and collectors are too short, your engine may never reach the rpm range where its providing much help to your power curve

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

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

http://www.carcraft.com/techarticles/11 ... ndex2.html

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

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http://www.summitracing.com/parts/FLO-C134218234/

http://www.summitracing.com/parts/HED-14044/
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IF YOU WELD STAINLESS EXHAUST PIPE without a back flush you can get weld crystallizing or SUGARING , an ARGON back flush and taping both ends to exclude oxygen helps reduce this significantly as will tig paste


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http://www.solarflux.com/Pages/Productinfo.html
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a well thought thru design on an (X) pipe and cut outs
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getting the exhaust back-pressure , measured in the collectors on the headers, below 2 psi at w.o.t. at 6500 rpm under full load would be one goal Id try to achieve,
that may sound difficult and it is if the mufflers are restrictive but it can be done ,
Ive done it with a couple cars with 3" exhaust systems with (X) pipes, and race type mufflers,
now I won,t say they were quite cars but they did not get me tickets as long as I drove carefully ,
and tried hard to never exceed 1/4 throttle and 3000 rpm on the street...
once your accelerator petals firmly on the floor, and the engines at W.O.T...
and your power shifting at 6500 rpm of course the noise level is significantly louder

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yes I had built and used a similar custom designed, or lets say extensively modified set, on my 1965 Pontiac le mans with a 496 BBC engine
they worked great!

the fast route is to buy these and carefully measure cut old headers and weld them on ,
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but due to the restricted clearances you are generally better off visiting a muffler shop and having them fabricate 8 short sections of expanded exhaust tube (they may need to be angled first) with both ends of a 2"-4" long length expanded to slide over each primary tube in the cut header and extension, obviously careful measurement is critical here
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https://www.summitracing.com/parts/flo-c178238300
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yeah its difficult but hardly impossible
http://garage.grumpysperformance.com/index.php?threads/x-or-h-pipe.1503/

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

http://garage.grumpysperformance.com/index.php?threads/high-flow-quiet-exhaust.10558/#post-45047

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

http://garage.grumpysperformance.com/index.php?threads/spiral-mufflers-anyone.10365/

http://garage.grumpysperformance.co...ave-resonator-tube-to-reduce-stop-drone.7590/
viewtopic.php?f=56&t=495

viewtopic.php?f=56&t=1166

http://garage.grumpysperformance.co...-descriptions-dont-tell-you.12357/#post-61139

viewtopic.php?f=56&t=1303&p=16831#p16831

side pipes without headers are mostly just for looks, in most configs its going to kill or restrict power,
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adding the full side pipe header and side pipe config without the inserts can provide very good power, and they were used on the l88 road racing corvettes as they provided the best power curve option available once correctly configured once the muffler inserts are in place, in the side exhaust, its a castrated exhaust, in the case of most inserts, but you can fabricate baffles that both reduce the sound and don,t significantly reduce power


one reason side exhaust on corvettes were and are used is the design allowed decent ground clearance AND long efficient header primary tube header designs.
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http://garage.grumpysperformance.com/index.php?threads/c3-side-pipe-exhausts.793/#post-30576

http://garage.grumpysperformance.co...impressed-with-dougs-headers.7831/#post-39146

http://garage.grumpysperformance.co...horty-and-full-length-headers.1303/#post-8221

http://garage.grumpysperformance.co...ng-to-take-awhile-but-theres-good-tips.15295/

http://garage.grumpysperformance.co...acing-entire-exhaust-on-a-c3.9296/#post-35280

http://garage.grumpysperformance.com/index.php?threads/spiral-mufflers-anyone.10365/#post-42721

http://garage.grumpysperformance.co...ource-for-fabricating-sidepipe-headers.13159/

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/
 
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Re: IM ALWAYS AMAZED AT GUYS THAT JUST SLAP ON factory HEA

S.D.C. said:
grumpy, I like the way side exhaust headers look on my corvette, but my mechanic swears they will not allow my engine to put out nearly as much power as a good under the car exhaust system would,my old side exhaust is getting old and rusted and the inserts are falling apart, I obviously will need to install a new exhaust system and the new side exhaust will be about $1300 vs about $800 for an under the corvette exhaust after pricing both out any ideas?



well the truth here depends on how your going to measure the horsepower and what components are used, both the under the car exhaust and the side exhaust can produce very good power, but personally i prefer the side exhaust, but I will point out that there's factors you must consider, a good side exhaust is generally lighter in weight and more efficient in my experience but its also usually strangled by the use of restrictive baffle inserts, its those inserts and the potential for you to burn your leg exiting the car on a hot exhaust that makes the side pipes less appealing, to many people..
inserts like these significantly reduce noise but Ive seen dyno tests where the insert removal was worth 90 plus hp, and it would more than likely be more if the car was tuned to take full advantage of the headers with the insert removed.
Ive seen custom inserts that were designed from preforated metal baffles that both reduced noise and significantly increased the power the side pipes produced, but I think theres such a limited market potential that not much research is going on,nor are there many options in over the counter side pipe insert baffles available.


inserts like these are what most side pipes come with and while they lower noise they hurt power over about 3500rpm in most applications
vette153.jpg



Ive always like the look of corvettes with well designed a side exhaust
but they get a bad reputation from guys who have girl friends burn the back of their legs exiting the car on hot side pipes, or guys that insist on running extremely restrictive inserts to reduce the noise who then bitch about the resulting loss of power

vette144.jpg

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Re: IM ALWAYS AMAZED AT GUYS THAT JUST SLAP ON factory HEA

Grumpy, I have a set of Flowmaster Weld on Merge collector extensions.
The 4 into 2 into 1. I think 1-3/4 or 1-7/8 and collector exhaust outlet is 3" .
They were given to me with a set of homemade Pontiac Ram Air 4 round port GTO headers.
Slip on extensions with weld tabs.
Forgot I had them.
New never used.
I have Hooker Super Comp Headers for the 87 Corvette.
Plan on using with my 410sbc for now till I can afford Stainless custom made headers or Take time to fabricate big tubes with a friends help.
Thinking now of using the Flowmaster 4-2-1's with Hooker Super Comps.
They are real short primary tubes as you recall.
Old school but bought at decent price & lightly used.

What is the correct orientation of the 4-2-1 collectors ?
Does Verticle position give bottom end torque ?
Does hornizontal give midrange & top end power ?

I can make it slip fit or weld fully myself.

The Stahl headers were best ever made.
Tried to have them custom make a set a few years back.
Economy forced them to shut down.
The Stahl 180 degree headers shown are a work of art & Performed like none other.
Legendary. With Pontiac Trans Am owners too.

Thanks Grumpy.

Brian R.
 
Re: IM ALWAYS AMAZED AT GUYS THAT JUST SLAP ON factory HEA

some simple fabrication work to graft on collectors like these, is required Ive generally installed them, indexed as the picture shows due to slightly better cross member and frame clearance considerations, I doubt it makes a great deal of difference because your not going to get a true equally spaced exhaust pulse config on both headers no mater how they get indexed, on most standard commercial headers, but what you do get is usually a noticeably wider rpm band torque curve
flo-c158218234.jpg

if you do the measuring, of the commercial headers and then do the math calculations and compare both, youll frequently find commercial header primary tubes are 4"-10" shorter than the calculations indicate would be ideal
http://www.superchevy.com/how-to/exhaust/0505phr-exh/

http://www.hotrod.com/how-to/engine/mopp-0412-tti-exhaust-system-and-header-components/

http://www.pontiacstreetperformance.com/psp/exhaust.html

http://www.pontiacstreetperformance.com/psp/exhaust3.html
adding an X-pipe to a dual 3" exhaust behind your muslecars engine is almost always going to result in a bit mellower exhaust tone and at least a couple extra horse power due to the slightly lower back pressure and generally more effective exhaust scavenging it can allow
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more numbers for ya'll who like numbers.
mufflercfm1.jpg

All tests via an independent lab
All tests @ 15” wc

2 “ Straight Pipe 283 CFM
2 ¼ “ Straight Pipe 365 CFM
2 ½ “ Straight Pipe 521 CFM

2 ¼” Typical Bent tailpipe 268 CFM
2 ½” Typical Bent Tailpipe 417 CFM

2 ¼” Inlet/Outlet_ Glass Pack Tips- No Louvers- Smooth 274 CFM
2 ¼” Inlet/Outlet- Glass Pack Tips-Louvered 133 CFM
Same as above set for reverse flow 141 CFM
2 ¼” Cherry Bomb 239 CFM
2 ½” Cherry Bomb 294 CFM

2 ½” Inlet/Outlet Dynomax Super Turbo 278 CFM
2 ½” Inlet/Outlet Ultraflow Bullet 512 CFM
2 ½” Inlet/Outlet Gibson Superflow 267 CFM
2 ½” Inlet/Outlet Flowmaster ( 2 Chamber) 249 CFM
2 ½” Inlet Outlet Flowmaster ( 3 Chamber) 229 CFM
2 ¼” Inlet/Outlet Thrush CVX 260 CFM
2 ½” Inlet/Outlet Maremount Cherry Bomb 298 CFM
2 ½” Inlet/Outlet Hooker Aero Chamber 324 CFM
2 ½” Inlet/Outlet Hooker Max Flow 521 CFM
2 ½” Inlet/Outlet Borla Turbo 373 CFM
2 1/2" Inlet/Outlet Magnaflow 284 CFM

http://www.pontiacstreetperformance.com/psp/exhaust.html

Standard OEM 2 ¼” Inlet/Outlet 138-152 CFM
Standard OEM 2 ½” Inlet/Outlet 161-197 CFM

this may provide some perspective when designing your exhaust setups and choosing muflers.
 
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Re: IM ALWAYS AMAZED AT GUYS THAT JUST SLAP ON factory HEA

grumpyvette said:
some simple fabrication work to graft on collectors like these, is required Ive generally installed them, indexed as the picture shows due to slightly better cross member and frame clearance considerations, I doubt it makes a great deal of difference because your not going to get a true equally spaced exhaust pulse config on both headers no mater how they get indexed, on most standard commercial headers, but what you do get is usually a noticeably wider rpm band torque curve
flo-c158218234.jpg

if you do the measuring, of the commercial headers and then do the math calculations and compare both, youll frequently find commercial header primary tubes are 4"-10" shorter than the calculations indicate would be ideal

Thanks Grumpy.
I will measure.
When I recieved my lightly used C4 Corvette Hooker Super Comp's Headers I couldn't believe how short the Primary Tubes & collectors are.
The Hooker Super Comps Round port RAM AIR 4 Headers are way longer.
Long collector. The TA always had a very wide powerband.
2,000-7000+. No matter how radical the cam profile was used.
Credit to the nice header design & true dual 3 inch exhaust I installed.
The Vette I may use an X pipe layout.
Flowmaster 4-2-1 about 12-14 inches long I recall.

Thanks again Grumpy.
 
Re: IM ALWAYS AMAZED AT GUYS THAT JUST SLAP ON factory HEA

So I tried out The Wallace Racing Header calculators Grumpy.
In theory I need about 30"inch long primary tube length.
1.92" inch ID primary tube diameter.
3.3" Collector diameter.

Or 30" primary length. 2" Inch primary tubes.
And a 3-1/2" collector.
Assuming 100% Volumetric efficiency. 410 cubic inches.
7000 Rpm Redline.
Right on target what I wanted original for my 1987 C4 Corvette.
I figured 28"-30" collector original.
Same specs as my 1970-1/2 TA round port Ram Air 4 headers are.
Just no one makes them.
Only Kook & Lemon Headers will make. Fork over $2000-3000.

Every C4 Corvette owner is getting screwed with aftermarket headers supplied current.

Will stick a tape measure down my C4 Hooker Super Comp Headers.
Get a Mean measurement.
Recalculate. 1St estimate......headers 10-12" inches too short for my 410sbc.

Also the Pontuac Ram Air 4
 
Re: IM ALWAYS AMAZED AT GUYS THAT JUST SLAP ON factory HEA

Also the Hooker Super Comp Headers Pontiac Ram Air 4 a perfect match on the 462ci - 455poncho as is.

Go figure. C4 Corvette guys get screwed.......crap.
 
Re: IM ALWAYS AMAZED AT GUYS THAT JUST SLAP ON factory HEA

I know from experience that adding those longer header extensions after very careful measuring and cutting and welding changes the sound , feel and effective torque curve , yes at times they will need to be angled or slightly shorter, or have the collector section angled or curved due to clearance issues
flo-c158218234.jpg

Ive generally tried to get a 36"-39" primary tube length as I find thats about the best result for a street/strip SBC
look take a 383, install a crower 00471 roller have about 10.5:1 compression

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

if you take a 383 with about 10.5:1 cpr and a crower 00471 cam and 1 3/4" headers (remember to add 15 degrees to the .050 lift duration to get valve seat timing)
crower00471.jpg


http://www.crower.com/index.php/chevy-2 ... -7041.html

http://www.crower.com/index.php/searchr ... 71&x=0&y=0


383header.png
 
Re: IM ALWAYS AMAZED AT GUYS THAT JUST SLAP ON factory HEA

I removed the Flowmaster 4-2-1 exhaust collectors tonight Grumpy from the homemade GTO headers.
Cut tubing off with my Sawzall few inches ahead.
Few tack welds to grind off in the morning.
23 inches overall length.
The C4 Hooker primary tubes measure 24-32"
All over the board.
Advertised as 26" primary length.

Some time to plan & think things over.
410 has a 3.800" stroke.
 
Re: IM ALWAYS AMAZED AT GUYS THAT JUST SLAP ON factory HEA

Lets Review all available current headers for a C4 Corvette with a 23 degree cylinder head style exhast flange.
We want to build a Car to compete against a Race Machine on Yellow Bullet Drag Racing Forum.
Not a show & shine Puts around making noise Calling its fast when a bone stock 2012 Ford Cobra Supercharged Mustang will eat 99.9% of C4 Corvettes owners For lunch. At the 60 foot starting lne the Super Mustangs already long gone.
Good driver with Drag Radial Tires. He clicked off a Low 10-second Run in 1/4 mile.

Lets Review more.
550-600 HP. 410 CI. Custom ground Crower grind. Inverse Radius Profile.
Race grind. Not a street grind.
Safe lowball redline 7k.
Crower Rods. Other good stuff inside.
Engine was built by my late bud Bill to beat a 10-second Track Camaro that street raced at night.
Never made it into his 85 Corvette.

Built 700R4 to take 600Hp by me.
In my 87 Vette.

IRS Dana 36 going bye bye.
Wil never hold up.
Had a Dana 44.
Realized never hold either. Rebuilt it & Sold it.

Bought a Competition Engineering Pro Magnum 4-Link Kit.
Full 4130-4140 Chrome Moly. One of the very best made.
1957-58 Pobtiac Olds 9.3 Rear will be used.
 
Re: IM ALWAYS AMAZED AT GUYS THAT JUST SLAP ON factory HEA

At least 2 3Rd members built. One with 3.64 gears Posi Street.
Track 4.10-4.88 gears Race Spool locked Axles.
28" tall tire. Drag Radials slicks. Nothing in driveline a weak link .

Current fancy C4 headers available.

Stainless Works. 1-5/8 inch primary tubes. Too small....
$1600 Waste of $$$.

Melrose headers. Stainless too. 1-5/8" primary tubes. Too small. again....
$1600 Waste of $$$$ again.

ARH or American Race Headers.
Stepped headers.
1-7/8" to 1-3/4". No primary length given. $1600 waste of $$$ again.

Leaves China copycats. We won't go there. Screw them .

Ok, Headman & Hooker Super Comps.
Old school.
Hookers known to fit good.
Very compromised design.

Want 2" primary. Can settle with 1-7/8".
3-1/2 Collector.
28"-30 " long primary tubes.
Nothing out there fits the Bill.

Only Hooker
 
Re: IM ALWAYS AMAZED AT GUYS THAT JUST SLAP ON factory HEA

Only Hooker Super Comps for a round port Trans Am.
Won't fit on a SBC.

SO WHAT'S A GUY TO DO GRUMPY ??
 
Re: IM ALWAYS AMAZED AT GUYS THAT JUST SLAP ON factory HEA

Hedman C4 Headers 1-5/8 primary tubes. No good also.

Hooker Super Comp 2151 has 1-3/4 inch primary tubes. Advertised 26" length.
3 inch collector.
Costed me used $125. Fleabay.
Dont feel so bad.....didn't waste $1600 on shiny stainless C4 headers that suck in design to begin with.
Its no small wonder to me Grumpy why C4 Corvettes have a bad rap for being slow........
Can't get high Rpm exhaust flow out with 400+ cubic inches.
They keep dinking with Factory IRS Rear too.
Never hookup & Pull a wheelstand with that......

BR
 
Re: IM ALWAYS AMAZED AT GUYS THAT JUST SLAP ON factory HEA

I think the answer depends on both your fabrication/welding measuring and cutting skills and your desire to try too maximize the engines power potential, I,m my experience theres no question, that if its done correctly youll make a bit more power, but it will also take some effort and might or might not be worth your time for the power youll gain.
now that might be anywhere from 15 hp to 50 more hp, dependent on the combo those headers are matched too.
and I don,t see the process of carefully fitting,the headers on the car, measuring and cutting the headers and cutting , trial fitting and welding the extended collectors several times (from experience) taking less than 4-6 hours, at 15hp that may be a waste of time in most guys way of looking at the time spent vs value gained,but the gains in lower rpm torque usually make taking the effort worth while, at 50hp I think most guys will see it as a really good move, but you won,t know what youll get until your done testing,and a good deal depends on the level of flow restriction past the collectors and ideally youll use an (X) pipe to blend the exhaust pulses as that tends to add to the torque curve by increasing exhaust scavenging efficiency, and yes I fully admit in some cases clearances under the car make the modification and resulting under the car road clearance a total P.I.T.A., making you wish you were never involved so measure very carefully and think about your skill level with a welder and ability to make precise cuts well before you start cutting up your headers to add longer 4-2-1 collectors, and don,t ignore the road to collector clearance issues!, its a whole lot easier to do the mods on a car that has decent ground clearance like a 67 GTO than a 1985 corvette!

IF you shop carefully youll find you have dozens of options for a STAINLESS 3" exhaust for your muscle car, don,t just jump on the first exhaust you find, actually compare what you get and cost and try to look over instructions and pictures
remember stainless costs more up front but easily last 3-4 times as long.
and your never going to get a true high performance car to perform to its full potential with out a decent exhaust
If your swapping to a larger 3" exhaust with an (X) pipe, it has or will more than likely reduced your engines exhaust restriction this tends to lean out the fuel/air ratio, which can reduce torque ESPECIALLY if you still have shorty stock exhaust manifolds that don,t always scavenge the cylinders correctly at all rpm levels, you can generally get back the torque and add upper and mid rpm power with correctly designed long tube headers, but most engines with factory injectors and tuning run rather lean for passing emission testing. and most original cams are more concerned with mileage and drive-ability than torque and peak power.
every change you make effects the way the car runs, if you reduce the exhaust restriction it potentially allows the car to make noticeably more hp, but REQUIRES there engines are re-tuned to match the new conditions and having a longer duration cam and larger injectors , or increased carburetor jet sizes and long tube headers certainly helps take advantage of the lower exhaust flow restriction.


http://www.highperformancepontiac.com/f ... ntiac_gto/

http://www.magnaflow.com/07techtips/pdfs/15898.pdf
http://static.summitracing.com/global/i ... 15898_.pdf
15898.jpg

67gto1.jpg

ponex5.jpg

http://www.summitracing.com/parts/pye-s ... /model/gto
pye-sga13r_w.jpg

ponex1.jpg

ponex2.jpg

ponex3.jpg

ponex4.jpg
 
Re: IM ALWAYS AMAZED AT GUYS THAT JUST SLAP ON factory HEA

I never lowered my C4 Like most have Grumpy.
The C4 convertible sits higher than the coupes.
The giant X brace has saved my fiberglass floor pans several times from road debris & steep driveways with a hidden potholes.
Still in the planning stages.
Most of parts bought for the 410 .
Common sense tells me to complete the solid axle conversion next.
So driveline is up to par for intended use.
I am not of afraid of fabrication or welding. As long as I planned ahead.
At least I won't lose HP & Torque.
I will use the 4-2-1 collector extensions.
 
Re: IM ALWAYS AMAZED AT GUYS THAT JUST SLAP ON factory HEA

I did some more online research Grumpy.
Big tube headers are available for a SBC C4.
1-7/8" with 3" or 3-1/2" collector.
EM. Exotic Muscle.
Mild steel. Ceramic coated.
Stainless available.
Someone had 1-7/8" step into 2" or visa versa.
Base price $1500.
I don't like how EM made equal length tubes on # 8 & #7 Cylinders.
Multiple S bends used.
Flow balance issue still..

Kook Headers will make what I want.
No one has stepped up to the plate .
I may be the 1st.
 
Re: IM ALWAYS AMAZED AT GUYS THAT JUST SLAP ON factory HEA

Stinky said:
Back in my younger days, a performance car just had to have dual exhausts.

Hypothetically speaking, if designed correctly, will a large single pipe perform as well as duals?
http://www.melrosecorvette.com/1984...er-system-no-egr-no-air-add-catalytic-option/
one of the better current c4 corvette exhaust system designs is made by www.melrosecorvette.com


your engine won,t know the difference between a properly designed dual exhaust AND A PROPERLY DESIGNED single exhaust, it SEES and REACTS to BACK PRESSURE and the cross sectional area and length of the exhaust, all those factors, can be calculated, for either design,

if your header collectors are 3" in diam. they have approximately a 6.7 SQUARE INCH CROSS SECTIONAL AREA, a y pipe feeding to a mandrel bent 4" exhaust with its 12.6" cross sectional area would provide virtually the same flow speed and resistance as a dual 3" exhaust, in fact a properly tuned single 4" feed from the dual 3" header collectors SHOULD produce a bit more uniform torque curve as the exhaust pulses are blended more uniformly so in theory scavenging may be improved. exhaust exits the engine in distinct high pressure pulses every 90 degrees of rotation this is not a consistent high pressure flow, the pulses exit like a chain, each link a bit separate but linked to the preceding and following pulse, or mass has the inertia of the fast flowing exhaust if properly timed by the cam timing and exhaust header design can significantly increase exhaust scavenging of the cylinder during the cam timing over lap, thus improving efficiency and the resulting power curve

tubingsizeversusarea.png

volumetric.gif

exhaustpressure.jpg

EXFLOWZ4.jpg

pistonposition2a.jpg


THINK THROUGH YOUR OPTIONS AND THE COMPLETE COMBO,
I see guys have long discussions about things like the difference in port cross sectional area or the best connecting rod length, to use, no one factor is going to make your engine totally dominate the competition, its a combo of small almost insignificant individual component choices being made and a good deal of time and effort taken during the assembly and clearancing work, that stack up to give you or prevent you from maximizing the engines performance.
you may not even think about factors like polishing crank journals, or valve train geometry or intake runner cross sectioinal area or length ,or intake runner port matching or surface finish, but the combined effects of your choices and components selected do mater!
look guys I think a good deal of this discussion is missing the point here, Ive built well over 150 engines in the last 45 years, (I lost cound decades ago)
but I can assure you that longer rods and the easily verifyable slight increase in dwell time, the longer rods produce will be totally meaningless UNLESS, you design the engine for and select components too take full advantage of the minor increase, by carefully calculating the REQUIRED compression ratio,fuel octane required,all the factors related to the cam timing,(duration,lift, LCA) you calculate and build and install, and tune the engine for , a matched exhaust header scavenging (header primairy length and diameter plus collector design) and the intake runner length and cross sectional area, to maximize the cylinder scavenging effects, plus you match the fuel/air ratio, and ignition advance curve, to maximize that longer dwell times potential advantage.
viewtopic.php?f=56&t=185
hre-h2021.jpg

THE NASCAR RACE CARS HAVE A MODIFIED SINGLE EXHAUST
DSC01540.jpg

related info
viewtopic.php?f=56&t=1166

viewtopic.php?f=56&t=495

viewtopic.php?f=56&t=3155
 
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Re: IM ALWAYS AMAZED AT GUYS THAT JUST SLAP ON factory HEA

NASCAR ALSO GAVE US OVALIZED EXHAUST TUBING.
DUAL 3" & 4" OVAL TUBING IS AVAILABLE .
Not inexpensive but I like the Hardware.
 
Re: IM ALWAYS AMAZED AT GUYS THAT JUST SLAP ON factory HEA

NASCAR Version of the Super T10 Shown also.
Or a JERICO 4-Speed Manual Trans.
 
choppe said:
Hi all, Does anyone have some good info on how to connect the ARP headers to the exhaust?

I have the magnaflow BB kit, the car is in the shop now, and they're having trouble finding anything that can connect with such low clearance between the pipe and floor. There's probably a little less than 1/2".



expiw.png


:thumbsup::laughing:

a good local exhaust shop can fabricate and weld up the required exhaust and make it look great, it just costs a bit more than most guys want to spend, the answer is buying and learning how to use a decent welder and finding a local supply for matching exhaust pipe, it costs a bit but in the long run the tools can save you far more and provide you with near limitless options
thats one in an endless list of reasons on EXACTLY WHY YOU BUY AND LEARN THE SKILLS TO USE A GOOD MIG OR TIG WELDER

honestly I get a couple jobs a month that require a bit of welding, and if I did not own several welders I go broke paying for the welds to be done, a decent welder pays for itself many times over.
you could easily fabricate an exhaust at less than 1/2 the cost a local shop may charge

http://forum.grumpysperformance.com/viewtopic.php?f=56&t=1730

http://www.eastwood.com/tig-welders-eastwood-tig-ac-dc-welder.html

http://www.welders-direct.com/mm5/m...e_Code=WD&Product_Code=907422&Category_Code=M


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

http://garage.grumpysperformance.com/index.php?threads/teaching-yourself-to-weld.8086/
 
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