Header Repair

Here’s the scenario: It’s early Monday evening. You are home from work and have finally decided it’s time to get back to work on the car. Saturday night was the race you had been dreading but knew was inevitable—the big wreck (insert your situation here). Now you are faced with some rumpled sheetmetal, a busted spindle and who knows what else in addition to a stiff neck. As you work your way through the flotsam and jetsam of broken race car parts you give the headers a quick once-over. No cracks or obvious breaks, so they must be good.

Unfortunately, racing headers are a lot more susceptible to damage than many people think, and it’s often a lot more difficult to detect than a crack or broken weld. That’s the bad news. The good news is stainless- and mild-steel headers can often be repaired to like-new status for a significant cost savings over replacing them.

“The headers can get extremely hot during a race,” explains Steve Sousley, owner of Pro Fabrication, a custom header shop. “That heat makes the tubing of the headers a lot easier to bend. If a race car gets into a wreck, a knock all the way down at the merge collector can bend the tubing up near the exhaust flange.” Sousley should know: In the seven years Pro Fabrication has been building custom headers for Winston Cup teams, he’s seen—and built—it all.

Header tubes are selected for one reason: performance. A circle contains the largest interior area for a given surface area of any shape. Want to evacuate exhaust gases from the combustion chamber as cleanly and efficiently as possible? Use a round tube with as few bends as possible. If for any reason the tubing becomes kinked, warped, squashed or anything other than perfectly round, the interior area of the pipe is reduced and so is its ability to flow exhaust gasses from the engine. Now we are talking backpressure. Also, to work effectively, header pipes must bolt to the head on a plane perpendicular to the face of the exhaust port. If pipes are bent so the header pipe mates with the exhaust port on an angle, performance will be affected. While small dings and even small flat spots aren’t a big deal for the Saturday-night racer, kinked or bent pipe is and should be repaired.

Detecting header pipe that has been knocked out of round is more difficult than checking for cracks. The best way to do it is wait until the headers are cool and use your hand to feel each pipe. Don’t always trust your eyes; they can deceive you. If you find damage, most problems are easily repaired if you can find a qualified header fabricator. Be careful using your local muffler shop for repairs. Making the proper bends for header tubing requires a mandrel bender. Good ones go for $50,000, and it’s unlikely you are going to find one anywhere except a specialized racing fabricator.

“Header repair is fairly straightforward and often preferable over going out and buying a new set,” Sousley says. “The headers I build are mostly for Winston Cup and Busch Series teams. They are custom to the engine builder’s requests and run about $2,500 for a set. Generally, I can repair a stainless-steel set of headers for $250 to $400 per side. Mild steel headers are even less: $150 to 250. So you can see there’s a pretty big cost savings, even over buying a prefab set out of a catalog. Merge collectors are pretty expensive, so even if that’s all you can salvage you still will come out ahead.”

Step one in the repair process is to cut away damaged sections of the header. Sousley uses any tool that best suits the situation, but most often sticks with a vertical band saw, a cutoff saw or a die grinder. New sections of tubing are then bent and cut to replace the damaged pieces. The compound curves common in equal-length headers often require several pieces, so Sousley uses what he calls “eyeball engineering” and a lot of small cuts to shave down the pieces of pipe until he finally gets what he needs. Every weld affects flow, so he tries to keep joints to a minimum. Also, “cheater” cuts hinder flow and must be avoided. All cuts must be made perpendicular to the direction of flow; a cheating cut is everything else. Cheater cuts can introduce angles into the smooth curves of your header pipes and also potentially reduce the flow capacity of the headers.

Before welding anything up, any heat coating that has been applied must be ground off because it won’t accept a weld. After the header is repaired it can be re-coated. All welding is done with TIG machines to keep the weld bead to a minimum. At least four tacks are made on each joint to make sure everything is held firmly in place. Sousley also cautions against using overly thick filler metal. Most pipe wall is between .049 and .065 of an inch; for TIG welding Sousley uses .035 filler rod and believes for MIG welders the filler metal should be around .025.