making headers???

[DRG]

Ok, I know you can make realisitc looking headers using solder.

I even understand I can make the collector from shim stock.

But how do you determine the bends needed as I am under the impression the bends have to do with the increase in HP.

Any and all help will be appreciated.

[MikeMc]

Ok, I know you can make realisitc looking headers using solder.

I even understand I can make the collector from shim stock.

But how do you determine the bends needed as I am under the impression the bends have to do with the increase in HP.

Any and all help will be appreciated.

Just make them fit around everything..... If we were 1:1 the length of the tubes / ID of the tube / air flow into engine/heads /class rules for exit......and so on. If you are doing an exact class or car get reference photos off Google or the web. The biggest trick with using solder is getting it flat...roll it between sheets of glass or plexiglass, then polish and bend. In this '31 the tubes are equal, and bent to shape then the collectors were added.

[Alyn]

These headers are known as 180° headers. They combine two tubes from each side of the engine into the same collector for even firing pulses.

They are scratch built out of aluminum rod however solder would have done just as well. The collectores are aluminum tube. The individual header pipes wouldn't fit inside the collectors at first, so they were pounded over a center punch to swedge one end open and then over the tip of a large phillips screwdriver to give them the squared off shape. Obviously, only one collector is on in this picture.

Bends by themselves don't help create horsepower. In fact, a straight pipe will flow better than one with bends. The bends are there to keep each tube the same length. That is why the rear tube on the drivers side loops up and then back down. This extra bending is needed to keep it as long as tubes towards the front of the engine. Keeping the tubes the same length helps to space the firing pulses evenly apart for better scavenging. Better scavenging = horsepower.

Years ago my cousin ran a circle track Camaro with 180's. They have a sound that is totally different from any other type of header. I wanted to duplicate his headers on this engine. This particular set was patterned after some pictures I found on-line (google 180 degree headers).

For the most part, all the bends in a set of headers will have a constant radius. Tube benders typically have dies that create 5, 6 or 7 inch radius bends. I picked one of these three sizes and calculated the equivelent in 1:25 scale. Then I found a rod with that diameter and used it as a bending tool for every bend you see in the picture. You don't need to go to this length to scratchbuild a good set of headers, but at least keep the bends similar by "eye ball". You'll notice that just about any picture of headers (or the real thing) will not have long flowing bends. They will all be consistently the same radius.

HTH or TMI; your call

[Eric Stone]

http://www.modelcarsmag.com/forums/index.php?showtopic=32561&view=findpost&p=324935

I showed how I made a set of headers in that thread. As soon as Fotki gets their problem fixed, the pictures should be back up (I hope). Hope this helps.

[comp1839]

header tubing bends are typically in the 3-4" radius zone. if you want to learn more, here is burns stainless' site.

http://www.burnsstainless.com/j-bends-2.aspx

[Jim Gibbons]

This article has probably more technical information than you want to know, but it's a really good overview of exhaust design, including headers. This is from the Mechanical Marvels column in Hemmings Classic Car magazine. Some key points in the article:

Frictional Flow Losses and Restrictions

A straight line is the ideal path for gas to travel. When bends are encountered, a loss of flow with internal pipe friction will occur. If a bend must be made, the gentler its shape, the less flow loss will occur. Tight right-angle bends are the greatest offenders and will generate the highest flow loss. Many automakers ignored this basic principle and placed numerous right angles in the exhaust system, especially in the case of a V-shaped engine with a single exhaust pipe.

A good rule for exhaust restriction is that the farther it is moved from the exhaust port, the less effect it has. A restriction in the exhaust manifold will degrade power more than a restriction near the tailpipe. Flow losses can be attributed to not only bends, but also to pipe diameter and internal wall surface. Cast-iron exhaust manifolds were produced with very rough internal surfaces that greatly increased flow friction. In contrast, the smooth internal wall of a header offers a reduction in friction.

After the collector, the exhaust system should comprise a pipe that is 50 percent larger than the primary tube diameter. Most large-displacement V-8 engines do well with 1¾- to 1-7/8-inch primary pipe, which would translate into an exhaust system with 2.625- to 2.812-inch diameter pipes.

http://www.hemmings.com/hcc/stories/2009/01/01/hmn_tips3.html

Edited September 2, 2010 by Jim Gibbons