If you think about it, headers are a lot like an induction system. As a means of transferring gases, they’re partly responsible for an engine’s behavior. They’re also greatly responsible for an engine’s image: Just as a multitude of carburetors can, a pair of headers will transform an also-ran into a front runner, if only aesthetically.
But headers differ from induction systems in a few critical ways. Whereas nearly any induction system will fit in most applications on its respective engine, headers are very specific to the car. Anyone with the gumption and some simple tools can make them fit anything but these deceptively simple parts have one shortcoming: their construction isn’t so plainly clear.
It is to Rick Carlyle, though. He learned the ropes with exhaust greats like Jerry Jardine and Frank Sanders (S&S). About 20 years ago he formed So Cal Engineering to cater exclusively to the hot rod business. He found immediate praise in the nascent revivalist movement for lakes-style headers that were exact in every way but one: His were near perfect, a consequence of modern budgets.
1. For these remote jobs,...
1. For these remote jobs, Rick Carlyle builds a fixture based upon the owner’s cowl and chassis dimensions. It’s not a bad idea even if the car is available if only because it raises the work height and offers a means to fixture the tubes so each side matches the other.
Though he largely hung it up when he retired, a special request inspired him to make another set. Chick Kozsis asked him to build a set to replace the ones he made for his blown Deuce roadster that got stolen from the host hotel’s parking lot at this year’s Grand National Roadster Show.
Carlyle has shown how he builds headers before but never to the extent that he did this time. Among the things he revealed was a very clever, if not unique, means to build them. You see, although Kozsis and Carlyle both live just a few miles from the border, they’re two different countries (Carlyle can see Canada from his kitchen). He mounted a mock-up Hemi block on a plywood board marked with the engine position and cowl and frame dimensions that Kozsis provided. It’s a system based on the one he used to build the headers for Royce Glader’s AMBR-contending roadster pickup, among others.
Carlyle favors lakes-type headers, specifically ones with big, curvy bends. The prevailing multi-tube, merge-type header design is touted to be more efficient than the lakes design because it can develop spontaneous low-pressure conditions after each exhaust valve shuts. But just because it can doesn’t always mean it does. In fact most off-the-shelf header designs generate little if any low-pressure conditions at all. So just because a lakes-style header is theoretically less efficient on paper doesn’t mean it’ll perform any poorer on the street. In fact, blown engines don’t benefit from the low-pressure effect at all, a trait that justifies zoomie-type headers on dragsters.
2. He begins at the source...
2. He begins at the source of the exhaust, the flanges that bolt to the heads. He also emphasizes quality for fit and thickness for leak-free performance. These measure 3/8-inch thick.
Engine parameters dictate pipe diameter but wall thickness is entirely up to you (although Carlyle suggests 16 gauge). He recommends delivering exhaust to the cone in sweeping bends primarily for aesthetic reasons, but it’s reasonable to assume the exhaust flows better than it would if delivered at a blunt angle.
He also suggests using mandrel-bent tubing. It maintains its cross-section, which improves performance. But more than that, the consistent cross-section means tubes can be cut anywhere along the bend and match others perfectly so long as the cuts are made along the bend’s radius. The crush-bending process, on the other hand, mashes the tube into an oval that matches nothing.
3. Exhaust ports are rarely...
3. Exhaust ports are rarely round yet tubing always is. Naturally the shapes must match. On most applications, like small Chevrolets, the tube can emerge straight from the port. This application requires that the tubes bend immediately as they leave the ports, hence these stubs.
4. To make them better match...
4. To make them better match the port, Carlyle hammers the stubs into a somewhat rectangular shape with a leather mallet.
5. Note that this stub assumed...
5. Note that this stub assumed a trapezoidal rather than oval shape as the ports are. It’s because the stub exits the port at an angle; the lower side of the stub needs to flare out a bit to meet the lower edge of the flange.
6. Carlyle made a number of...
6. Carlyle made a number of tools for specific purposes; in this case to form the edges of the stub. This particular tool made from a Porsche strut shaft has a radius that nearly perfectly matches the ports’ corners.
7. Note how hammering the...
7. Note how hammering the stub on the strut shaft rounded the previously sharp corners. That had the unintended consequence of stretching the metal, which jogged the longest edge of the port.
8. He solved the jog by hammering...
8. He solved the jog by hammering it on a flat tab welded to the side of his worktable. Usually a good stub fit is a trial-and-error process with repeated trips among the various forming tools.
9. Note that Carlyle also...
9. Note that Carlyle also sharpened the upper corners while he was at it. Also note how the hammering thinned the tube’s wall, another good reason to use thicker 16-gauge materials.
10. The stub actually slips...
10. The stub actually slips inside the port, a fit that better explains the odd shape of the stub. Specifically the opening has to be narrower at the inside of the radius to clear the upper part of the flange and wider at the outside of the radius to meet the lower part of the flange. The flange’s upper edge interfered with the stub’s tight inner radius so Carlyle filed it to fit.
11. Fixtures like this ensure...
11. Fixtures like this ensure fit and improve side-to-side consistency as they hold the pipes securely in place. Note that Carlyle orients the tubes’ and cones’ weld seams down and toward the engine a bit so they aren’t visible from eye level. Just don’t point the seams toward the engine; it’s visible and tougher to fit primary tubes.
12. He mounted a stub and...
12. He mounted a stub and cone and plotted his cut lines. The bent tube in this photo is for display only as the seam would ordinarily point down.
13. This photo is actually...
13. This photo is actually from a few steps ahead but it shows something critical. The manufactured end of the cone measures about 1 5/8 inch but this header’s pipes measure 2 inches, meaning Carlyle had to trim them to fit. That his flanges measure 3 1/2 inches means he can’t cut the big ends. So this is as short as he can make a header, which underscores the reason to start with the rearmost-offset cylinder bank if the shortest, matching-length headers possible are the goal.
14. After locating the cone...
14. After locating the cone and fitting the primary pipe and stub Carlyle tack-welds the joints among them. This way future processes won’t threaten the careful fit he’s developed so far. But note that he doesn’t fully weld the pipes as he may have to disassemble them.
15. Carlyle proceeds with...
15. Carlyle proceeds with the other primary pipes, making stubs for each. He marks a general cut line on half of a U-bend. Note that he leaves the straight end just long enough to overlap the stub yet not long enough to hit the engine.
16. There’s no set way to...
16. There’s no set way to cut pipes but Carlyle favors a high-speed, wood-cutting band saw, of all things. The intense friction from the blade, not the cutting action of its teeth, actually burns through the metal. It looks scary and sounds terrifying but works amazingly well.
17. Carlyle emphasizes that...
17. Carlyle emphasizes that a cut pipe never ever fits without extensive work so expect gaps at first. He says he typically fits each successive primary pipe out of habit yet fitting the rearmost primary pipe as he did here locks in the header’s general shape.
18. After marking the interferences...
18. After marking the interferences Carlyle removes the pipes and sands them. Note that he uses every part of the belt, like around the wheels and over the edges of the belt (as seen here).
This construction is open to several welding processes. Of course GTAW (TIG) requires the least finishing, which is why Carlyle favors it. But GMAW (MIG) and FCAW (flux-core) will indeed suffice, provided you don’t mind ropy beads or lots of grinding. But there’s an even more appealing option: The flanges withstanding (which work best with GTAW and almost as well with GMAW), this is an application practically made for oxyacetylene welding.
Acetylene welding is appealing because it produces weld beads barely harder than the base metal. That’s good because soft materials move readily. And whether by heat cycling or engine vibration the metal in headers moves quite a bit. The boundary between the soft pipes and relatively hard electric weld beads concentrate stresses that often cause the metal to crack adjacent to the weld. Gas can produce beautiful, small welds but it just takes more practice.
19. Making the entire tube...
19. Making the entire tube fit the cone perfectly isn’t ideal because the angle between the primary and the cone is less than 90 degrees. Instead, Carlyle fits the “heel” perfectly and lets the “toe” run long and curl away from the cone (as seen here).
We’ll also expand upon another piece of advice in the captions but here it is in a nutshell: start with the side that has the rearmost-offset cylinder bank. One bank of a V-configured engine sits slightly behind the other. With a few exceptions (big Olds, Poncho, and the late OHV Caddy for examples), this means the passenger side, and on some engines, the offset is huge (roughly 3 inches for big Chevys).
Doing so establishes the forward-most position where the header ends. Start there and you can lengthen the other side’s header to match; however, if you start on the forward-offset side you may not be able to shorten the rearmost offset header to match.
Beyond that, though, the world is your canvas: primary pipe angle and length, cone angle and length, and construction style are open to your interpretation. As Carlyle worked he explained how fit and style largely prevail in lakes header design. Get a grasp of those and a mastery of some simple tools and you’re guaranteed a header that’s unique, just like your car.
20. Carlyle has another mandrel,...
20. Carlyle has another mandrel, this one a heavy-walled pipe about 1 1/2 inches across, welded to a flat bar that he clamps in his vise. With this and a hammer he can flatten the toe of the bend down to better follow the cone.
21. The net effect of this...
21. The net effect of this process reduces the angle of the bend, at least at the toe. Cutting the tube further up has the same net effect of reducing the angle but it also eliminates the gradual taper that makes each tube seem to flow into the cone.
22. Altering the angle also...
22. Altering the angle also unintentionally changes the tube’s diameter at the toe. In this case the diameter decreased, which disrupts the tube’s fit against the cone.
23. Another trip or two to...
23. Another trip or two to the belt sander removes the gaps. Carlyle uses the instincts he’s honed over the years but you’ll probably want to mark the areas to be sanded. At the very least remove the smallest amount of material each time.
24. Move slowly and you’re...
24. Move slowly and you’re almost guaranteed a perfect fit. While gaps can be filled by welding it’s a better idea to make the tubes fit tightly. That assures a stronger, better-looking joint.
25. Just as he did with the...
25. Just as he did with the leading primary tube, Carlyle cuts the remaining primaries to fit between the stubs and the cone.
26. Earlier he tacked the...
26. Earlier he tacked the leading stub and primary to the cone. This time he just tacked the primary to the stub. Instead, he simply marked the fit between the primary pipe and cone.
27. Only after he fits all...
27. Only after he fits all the tubes does Carlyle cut their openings. He simply transfers the shape to the cone and cuts out the appropriate size. He bores the ends with a big drill in a press.
28. Any number of methods...
28. Any number of methods can connect the holes but Carlyle favors a pneumatic nibbler. He does, however, clearance the jaws so the nibbler will cut highly curved surfaces.
29. He then finishes the opening...
29. He then finishes the opening with a sanding barrel. Resist the temptation to make the hole exactly as big as the primary tube. The engine will never notice that slight overlap but you’ll appreciate it come time to weld the joints together.
30. Welding on perfect edges...
30. Welding on perfect edges is tricky, especially when a pipe obscures the exact location of an edge. The slightly smaller openings in the cone act as a bit of a heat sink, which reduces the incident of blow-through. That’s particularly comforting if welding with acetylene.
31. Here’s why Carlyle can’t...
31. Here’s why Carlyle can’t cut the big end of the cone: his flange would be too big. And likely you can’t for the same reason if you use a ready-made flange. In fact, the same holds true if the cone merges into a pipe. Of course all bets are off if you’re dumping the headers into the open.
The final product is not just functional, it’s quite beautiful. And if Kozsis measured right, they’ll fit as if Carlyle built ’em on the car.