I'm asked this alot. Nothing ever happend to them, they just faded away.
In theory, headers are designed to extract the exhaust out of the exhaust port better than the stock headers. Although I have seen some that don't do that, the vast majority of tubular headers will do a better job than the stock or OEM exhaust headers.
If you go back to the early days of drag racing (the early 1960's for instance), most race cars favored open pipes, one from each exhaust port. In some classes, such as the Gasser classes and the Street Roadster classes, NHRA mandated that the headers from each bank had to terminate in a common "collector". This would mean that a V8 engine could only have two header openings, one on each side. But NHRA failed to define how large an opening the collector could be. Some creative racers fabricated a "collector" large enough to go around all four pipes on each side.
This is a perfect example. A piece of mettal wrapped around four straight pipes constituted a "legal" collector, one on each side. Anyone could see that it was just four straight pipes, and the collector was designed to just meet the rules. Eventually, NHRA realized that it would be better to just permit the straight pipes and be done with it.
But not in the Super Stock or F/X classes. Up until 1963, open exhaust was permitted provided that the opening (the collector) was not larger in diameter than the stock exhaust pipe. Some of the OEM exhaust pipes (or head pipes) were only 2" in diameter, a few were only as large as 2 1/2". It was difficult to get four seperate primary pipes to neck down into a 2" diameter collector or even a 2 1/2" collector. That's when the header fabricators started to use the Tri-Y-Header design. Four primaries into two slighly larger pipes, into the head pipes. 4 into 2 into 1. It worked and it was better than the stock headers. Of course, there were the usualy racer complaints in S/S and F/X. Some factory exhaust systems had larger diameter head pipes than others, so the cry was that they had an advantage. In 1963, NHRA revised the open exhaust rules in S/S and F/X and allowed everyone to use a maximum of 3 1/2" collectors. That is when the 4 into 1 header started to really take off. It worked better because a properly designed collector alowed better "scavenging", the ability of exhaust pulses to create a partial vacuum going through the collector and "pull" the next pulse out with it. It was not as if there had been anything wrong with the Tri-Y design, it was that the 4 into 1 design worked better and made more power...
In theory, headers are designed to extract the exhaust out of the exhaust port better than the stock headers. Although I have seen some that don't do that, the vast majority of tubular headers will do a better job than the stock or OEM exhaust headers.
If you go back to the early days of drag racing (the early 1960's for instance), most race cars favored open pipes, one from each exhaust port. In some classes, such as the Gasser classes and the Street Roadster classes, NHRA mandated that the headers from each bank had to terminate in a common "collector". This would mean that a V8 engine could only have two header openings, one on each side. But NHRA failed to define how large an opening the collector could be. Some creative racers fabricated a "collector" large enough to go around all four pipes on each side.
This is a perfect example. A piece of mettal wrapped around four straight pipes constituted a "legal" collector, one on each side. Anyone could see that it was just four straight pipes, and the collector was designed to just meet the rules. Eventually, NHRA realized that it would be better to just permit the straight pipes and be done with it.
But not in the Super Stock or F/X classes. Up until 1963, open exhaust was permitted provided that the opening (the collector) was not larger in diameter than the stock exhaust pipe. Some of the OEM exhaust pipes (or head pipes) were only 2" in diameter, a few were only as large as 2 1/2". It was difficult to get four seperate primary pipes to neck down into a 2" diameter collector or even a 2 1/2" collector. That's when the header fabricators started to use the Tri-Y-Header design. Four primaries into two slighly larger pipes, into the head pipes. 4 into 2 into 1. It worked and it was better than the stock headers. Of course, there were the usualy racer complaints in S/S and F/X. Some factory exhaust systems had larger diameter head pipes than others, so the cry was that they had an advantage. In 1963, NHRA revised the open exhaust rules in S/S and F/X and allowed everyone to use a maximum of 3 1/2" collectors. That is when the 4 into 1 header started to really take off. It worked better because a properly designed collector alowed better "scavenging", the ability of exhaust pulses to create a partial vacuum going through the collector and "pull" the next pulse out with it. It was not as if there had been anything wrong with the Tri-Y design, it was that the 4 into 1 design worked better and made more power...