So my truck has a 1970 318 with a mild cam intake and Holly 650? It already has a custom exhaust but for some reason no headers. Will I really be seeing any HP gains with headers?
:ughAllowing a motor to breathe better? Anything the same size as the individual exhaust ports is more than adequate. If you blow through a straw, you will have resistance. If you blow through a straw with a giant cone on the end, you will have the same resistance. The cone (header) doesn't make more air magically flow through.
Headers change the WAY the air flows out the ports, not necessarily how MUCH air flows through. That's why they sound different. Even then, it won't make much difference unless the motor is pushing a LOT of gasses through (5-6k+++ rpms). For a motor to do this, it will need more than just an intake and carb. It will need a different cam, valves, stroke, etc. That's what makes a "race" motor...
I understand how headers work, I'm not an idiot.
I also understand that engines work like air pumps. You can bolt all the fancy crap you want on them, and they absolutely cannot produce any more air until you change the internal components. There is a mechanical limit, until you change the mechanics.
Hence: stock vs "race" engines. Stock engines have an internal mechanical limit to airflow, and a "race" engine has the internal mechanics changed, to produce more airflow, requiring extreme changes to the entire exhaust system.
You just don't get it do you. I was going to post a link of a comparison that was done on a motor. Same everything but it was dyno tested before and after the stock manifolds vs the headers. You are right it won't produce a 100 hp gain just about 80! With nothing but a header install!The manifolds do not create as much of a choke-point as people think, that's why headers don't magically add 50 hp. You are only increasing the size of the "tube" by a tiny bit. Anything larger than the size of the actual exhaust port probly won't make any difference.
5, 10, 15 hp? I don't see why not... It still isn't a significant difference and I don't see why people can justify spending hundreds of dollars on a minimal power increase. Which is why I played devil's advocate and told the other half of the story...
:thatfunnyI understand how headers work, I'm not an idiot.
Stock exhaust manifolds DON"T do this! You are missing the point. NO engine components need to be changed to benefit from headers! Read the entire article....Well-designed headers produce a "scavenging" effect. When an exhaust gas pulse exits a header tube into the collector, a negative pressure wave is created that travels back up the header tube to the exhaust port during valve overlap. This negative pressure helps pull any remaining exhaust gas from the cylinder and also helps draw the incoming intake charge into the cylinder. This, of course, is very beneficial to engine performance but the tubes must be long enough for it to be effective during a useable rpm range.
This is another point I've been trying to make. You have to get the RIGHT header for the RIGHT rpm range to get the most out of the upgrade. From the little I know, the engine has to be making most of it's power at a higher rpm in order for the headers to be used optimally.Well-designed headers produce a "scavenging" effect. When an exhaust gas pulse exits a header tube into the collector, a negative pressure wave is created that travels back up the header tube to the exhaust port during valve overlap. This negative pressure helps pull any remaining exhaust gas from the cylinder and also helps draw the incoming intake charge into the cylinder. This, of course, is very beneficial to engine performance but the tubes must be long enough for it to be effective during a useable rpm range.
Here is another good point. Most people who install headers, have to make significant changes to their ENTIRE exhaust system. They don't just change headers alone... The change of the exhaust sytem, from the collectors-back, is where people see the biggest difference in performance. The stock muffler, cat, and all the poor factory tubing bends restrict more than manifolds ever could...However, as we will see, the quality of manifold exhaust flow varies from vehicle to vehicle. Regardless of the manifold, we recommend that before you install headers you make the rest of the exhaust system less restrictive. This usually means installing larger diameter, mandrel bent pipes and definitely means using more free flowing mufflers. It doesn't make any sense to put headers on if the exhaust flow is only going to be choked further down the line.
Once again, we need to weigh the costs and benefits. Is it worth spending around $250 +++ on a decent set of long tube headers? If it were me, I would wait till the engine actually NEEDED them before dropping that kind of coin... However, I completely understand if someone installed them because they looked and sounded different, but don't expect a miracle performance bolt-on!The aforementioned scavenging effect is most pronounced on long tube headers, however these headers are usually more expensive, the most difficult to install and take up the most space. Long tube headers require that the exhaust pipes be cut and flanges attached that will connect with the header collector.
That sums up just about everything I've been trying to say. Straight from your article you wanted me to read. There is a maintenance factor, you get what you pay for, there are mechanical limitations of the rest of the engine system ("camshaft design, intake system, CYLINDER HEAD PORTS"), and the website says approximately 10 HP gain...Steel headers will not last very long unless they are coated. The paint they are delivered with is just something to keep them from rusting in the box; they must be painted with high temperature paint before they are installed. Even that kind of paint won't last however, and they must be periodically recoated or they will rust away. Stainless steel headers will not rust but they will usually turn blue near the head flange. Ceramic coatings are durable and can withstand higher temperatures. A quality set of headers will have a substantial head flange to prevent exhaust leaks and all connections will have high quality welds. Finally, an engine works as a system, and the effectiveness of individual components is therefore very dependent on the other parts. While long tube headers are generally better for maximum performance than short tubes, the amount of power increase either type can provide depends on the camshaft design, intake system, cylinder head ports, and how restrictive the stock exhaust manifolds are. In general, a quality set of headers should provide an increase of approximately 10 horsepower, and if you're restrained with your right foot, you may even see an increase in fuel mileage.