I am surprised at some of the posts I read here ,,, for generations one of the first things to do when trying to get more speed , hp and torque is to increase the amount of fuel/air into the engine to create more power , hence the reason engines began to be increased in engine displacement size , Not so good for mpg , but that was not the goal , the goal was more power.
Nowadays with the advent of the computer designed engines factory roller cams , better sequential fuel injection and various technologies we can now make good power with smaller size cubic inches . Carbs ruled in their day , but that was yesteryear , they can still be made to run strong , but it does not make for as an efficient running of an engine and equal the mpg of modern SEFI . Back in the days of carbed engines one of the very first things to do to increase power was to get the exhaust opened up and let the engine breathe freely .
Switching from single exhaust to duals was a 15 -20 hp increase and then adding a 4 bbl carb in place of the 2bbl carb was another 15-20 hp , and could be more depending on who built the carb as there was people like Barry Grant that could squeeze 50 additional ponies out of a carb just by the way he built it , But forcing more juice down the throat of an engine without opening the exhaust for better breathing was really quite useless because it would create a bottleneck .
Step up from plain duals to headers , now you can increase hp to at least 15 hp or more depending on the setup . But it will depend on the design of the headers as to what hp torque you get . On the street one needs long tube headers because of the use of low to mid range rpm band , the short tube headers will push the torque increase into the higher rpm range , so in order to see the benefit of short tube headers the engine needs to see the high prm ranges not usually found used on the street but mostly on the race track which is why most race cars will have short tube headers ,On the street you really need the torque/hp at the low rpm range in order to successfully launch at the start or tow a trailer .
Headers are a tuning luxury so to speak , they are not necessary for most applications on the street . The main reason if not the only reason tuned headers are not on all factory production cars is because of design/testing and warehousing costs because there are so many different
engine /body/chassis designs of so many different models of cars would mean that car makers would have to spend hundreds of thousands if not millions of dollars to design and test the best header design for every make model and chassis design there is . This cost would then be added to the cost of every car . The term "tuned headers" is specifically called that because each individual primary tube on the header is specifically "tuned" for a specific engine/chassis . The length , diameter and shape/bend of each primary tube is tuned and tested on a dyno to find the most torque and hp for a given engine and vehicle design . Even though having the very best tuning for a given engine does not mean it will fit every vehicle that engine come in . this is the reason that car makers only make 'factory headers' on very specific High Performance cars in their lineup , as they just want to show what can be done to increase performance in their cars .
The cost factor that a factory would have to implement to design ,test , for all their cars would be much higher than an aftermarket setup . If you examine the aftermarket offerings you can find headers priced from a hundred bucks up to 1500 bucks depending on what brand , material and how well tuned it is as some aftermarket companies only make some sort of knock-off ;something that they can sell to the average guy who wants headers for a hundred bucks .
Any time a person wants to make real power from their vehicle it is necessary to calculate out what exactly do they want and what is needed to get it . Just throwing a big monster carb on an engine just may drown it with too much fuel , just as when putting on headers , it needs to be calculated out on the specific vehicle , You can't just put a set of racing tires on a car and then call it a race car . :lol:
Originally when computers were put on cars it was to monitor fuel and emission output to make a cleaner burning engine system to reduce the hydrocarbon emissions in the air . The OBD system , On Board Diagnostics were to aid in measuring and adjusting of the fuel/air ratio , engine knock and timing on the lean burn engine design of modern cars and has evolved into a system that can allow a person to dial in specifics to get an exact tune that they want for their car . There is a default factory setting , just like there is a default setting on your home PC, and there are software tools that a person can use to make a custom tune setting to fir their desire.
If a person wants to make changes such as adding headers , changing fuel system components to something that is not a factory setup then it will be necessary to understand how to make these tuning adjustments to make the best use of their hardware changes . The OBD system is a great system as it gets more specific detailed info for the tech to better understand what exactly is happening in their engine . In the old days when a tech needed to do a tune-up they had to replace the points in the distributor and would use an analog dwell meter to dial in the correct dwell for best operation , since electronic ignition came in , setting the dwell is no longer needed as it is done automatically by the electronics in the system . OBD is just the next step in the electronic evolution in today's cars . If a person resists and chooses not to learn the use of today's modern tools it is to their own disadvantage .
I may have missed something about the statement about the tuner program that costs 1 -2 grand , as great ones can be had for 5-7 hundred , but that is because it is for OBD2 , OBD2 has at least 14 different protocols , which is way more than OBD1 and OBD2 requires a hardware interface between the car and the laptop , while OBD1 does not need anything but a cable between the car and laptop ,,and the tuner progs are low cost and some are free .
In earlier days people had no choice except to buy a high dollar pre-programed chip to get a performance increase and that was a standard default setting for that chip , if a person wanted to make changes to their car performance to a higher level they either had to send in their chip to get it programmed again , or buy yet another chip ;Going that route is far more expensive than using an OBD tuner prog where you can make changes anytime you want without paying any additional costs and not even remove anything from car , just simply hookup your laptop and tune . I do not mean any disrespect to anyone , but just trying to open up a field of understanding .
I love the old 70's muscle cars , but I rarely see any on the road these days , when I do there are either a classic restoration where they take it to car shows or only drive it in the summer time and park it in the winter,,,,,or it may be just an old beater rust bucket that still is running good , The reality is this is 2011 and computer cars have been around for more than 20 years and we will never ever go back to the days of leaded fuel and carb'd cars in production vehicles . The likelihood of being able to commonly find a performance carb'd car that is in really good condition that does not need restoration and is not needing repair for 1000 dollars is almost nil unless buying from someone who does not know what they own .
Most of the cars from the 70's are gone to the salvage yard , very few are running around today and notice what they are , mostly some sedan that grandma drives or a car that is in some serious need of paint and body work .
In regard to the HP ratings that came from factory ; well before 1972 the way the HP was measured was not in a car at all ; it was mounted on an engine stand with no A/C , no PS , no power accessories , no full length exhaust system , and no transmission attached . This is what is called Gross HP .
. After 1972 the way the HP is measured is with engine installed in a car with A/C air , Power steering , any and all power accessories attached , with exhaust system and with the transmission attached , installed and the power measured at the tailshaft . This is called NET HP , NET HP is a more realistic measure of the HP that is available to the driver . So when you see HP numbers comparing between the Gross & Net numbers , the reality is the engine that can produce 300 Net HP , is actually producing more HP than an engine that produces 300 Gross HP
If we take a close look at today's muscle cars , we can see that they can produce 350 Net Hp
and still get 25 mpg, no 70's muscle can do that .
I just read and article of the 2012 Camaro factory stock supercharged at 556 NET HP
and a V6 at 323 Net HP
I have not seen or heard of any V6 non-computer controlled car that can produce even close to that amount of power .
With these statistical facts..... to think that a carb'd factory car has anything superior over today's computer muscle machines is something to rethink and come to the realization that today's computer muscle is Far Superior too any factory carb'd car .