After you’ve been building and modifying cars for a while there’s some things that you become pretty particular about. It could be just how you like something to look or function, or just an extra step you take to save yourself headaches in the future. One of mine is an exhaust system that’s leak-free and sounds good. I’ve had bad luck over the years of header unions leaking over time. It seems either they crack at the welds or they just fit poorly and leave much to be desired when fitting the rest of the exhaust.
There seems to be two common header unions out there, the “ball and socket” and a triangle shaped flange with a gasket that goes between. The ball and socket style has a rounded “ball shaped” end on the header and a small piece of pipe with a female portion that fits over the socket and a bolts on flanges on either pull them together. Some of the lower end headers tend to come with the ball portion in bare metal and some come with a fiber gasket/coating. Both of these tend to either leak right out of the gate or after a short period of time. Forget even trying to run an old used header! The triangle flange style works ok with a gasket bolted between the parts, but it has NO flex and I’ve had them crack at the welds for the flange over and over again. I decided to show my solution that has solved my header leak issues over the years.
On Project Pilehouse I have a set of shorty S10 V8 conversion headers (the truck sits on an S10 chassis) and since I don’t have an exhaust bender or a lift easily at my disposal I’m going to have some friends at a local exhaust shop fit up an exhaust to the truck. My drivers side header has the steering column running through it and requires disassembling the column and I didn’t want them to have to deal with all of that. I decided to build the exhaust from the headers and get it down under the truck where they could easily build the rest of the system back on the lift.
These headers had a 3 bolt flange and I started by using a reciprocating saw to cut the flange off. I had to make the cut extremely close to the flange itself as the collectors for the headers were only a few inches from the flange and I needed space to slip the end of the flex joint into the header.
Above are the flex joints that I like to use. They have a stainless mesh flex section that gives you a lot of flex for engine movement. They are also extremely strong and won’t crack or fail like a fixed joint would. These can be found online through many parts vendors by searching “mesh exhaust flex joint” or a well stocked parts store or exhaust shop should stock these. They are commonly used to repair OEM flex joints as they’ve become the standard flex joints on many modern cars.
For strength I decided to slip the flex joint inside the header. If you have an exhaust spreader handy you can flare the end of the header, but in my case I was working late at night and mine seems to have walked off! I decided to keep working and did an ultra basic method of flaring the metal with a crescent or adjustable wrench. I slowly worked my way around the edge until I had a large enough flare I could slip the flex joint into. Now this method will leave small dents in the metal, but if you’re careful they’re pretty light and can be sanded out.
Once I had the ends flared out I slipped the flex joint (I had to use a rubber mallet as the slip joint should be a tight fit) into the header and used a hammer to tap the metal tight all the way around the new flex joint. I then made sure the joint was sitting even and wasn’t cocked up, down, or side to side. With everything sitting how I wanted I put a single tack weld to join the two pieces. I then trued the joint up again (it will tend to move a little from the heat of the first weld) and put a second tack weld 180 degrees from the first.
With the flex joints secured I could work my around the union and weld it up fully. I chose to TIG weld the pieces together with the TIG 200 AC/DC, but a MIG welder will work ok as well. Just make sure that you COMPLETELY grind the aluminized coating off of the parts you’re welding if using a TIG as it will tend to pop and weld dirty. With a MIG you can burn right through the coating no problem.
With the flex joints welded I bolted the headers back on and used TIG wire to make templates of how I needed the short pieces of pipe to come out of each flex joint to get the exhaust down next to the frame and under the cab. I had the local shop bend me up two pipes to match and I fit and positioned them at the correct angle. I pulled them back off and fully welded those to the flex joints. The result is a set of headers and down pipe custom made for Pilehouse that will allow for a full exhaust to be fabricated.
The last step was to spray the header and dow pipe with Eastwood Hi-Temp black exhaust coating. I reinstalled everything and ran the truck for 5-10 minutes to cure the high-temp paint (it needs to be heat cured and puts off some smoke/fumes until cured). I really dig the subdued satin black look and it almost sounds too good to put mufflers on!