I'm getting ready to do my exhaust on my 68 F100 Custom build ( https://www.ford-trucks.com/forums/1...l#post21682794 ) and was wondering if I should add a small 4" section of flex pipe coming off the headers for movement. I don't expect much movement since I did old school motor mounts using urethane bushings. None of these old trucks had them. The failures were normally at the donut gasket off the manifold. There seam to be several different types with the braided flex being the most common on newer vehicles. My headers have the ball/cone connection with a internal sleeve for straight flow. I still have to add the O2 bungs after the header connection. I'm using the interlocking V Band exhaust clamps where I want to separate the exhaust for removal. I'm planning for it to come apart in 3 pieces. All joints welded up, trying to stay away from band clamps. The front section will be from the headers/H-pipe to the muffler inlet. The muffler back will the other 1/2. The exhaust will exit in front of the rear tires. Unable to exit out the back due to clearance issues with gas tank and Watts system. The lower Watts bracket is causing the holdup, any lower and its lowest hanging item.

Summit racing show the different type https://www.summitracing.com/search/...ust-flex-pipes

So add them to help reduce vibration or not?

 

Flex joint yes, bellows joint no. I would contact pypes exhaust or magnaflo and check with them, imagine the quality might be better than the summit ones, O'Reilly has flex joints as well.

 

Excited to follow your progress on this because this project is a future one on my list. I just received my new set of FPA headers that will be the catalyst for doing this. Can you provide some additional details on your approach? Are you MIG or TIG welding? What V-Band clamps are you using? What mufflers are you going with? What type of pipe are you using and where are you getting it from? I am a newbie welder but have both MIG and TIG welders.

 

I bought a 2.5" builders kit from Speedway motors and added 2 extra straight pipe and H-Pipe. This kit is 304 ss, 16ga (0.062") thick which makes welding a little easier The kit contains 4 each 180, 90, 45 and 4 straight pieces. The kit is set up for band clamps (slip joints) but you just weld instead of using band clamps. You can actually use a mig welder here if you want too. Band clamps can really run the cost up since one is used at every joint. The V-Band clamps are designed to weld on but all you do is a fusion weld without having to add filler metal. They also separate a lot easier since you only have to move the joint back about 1/8" once the clamps are removed. I haven't decided if I want to cut the bells off and do a butt weld for a cleaner look. I do know I have at least 4 joints that need to be butt welded due to space restrictions. You do need to run a Argon purge gas inside the tubing while welding. For mufflers I went a 3 chamber SS since I want it fairly quite. These are 2.5" and 2.5" out no packing so they should have a little rumble to them with little restriction in flow. As I have gotten older I like things a little quieter now. PN's: 910-13013, 930-2004, 910-13843, 910-13890, 910-13828

Now if you have not dealt with SS, it is harder to cut and work with. Hard on blades since it work hardens. So once you start a cut you want to finish or back off and don't let the blade heat up the SS.

I wish I had a big band saw to cut the exhaust, but I don't. For straight cuts I have a special 14" blade for my chop saw to cut the SS. I also have a portable band saw I can use or cutoff wheel on my grinder.

As far as starting, you start at the headers and work your way back. With truck you have a little more room than a car to work with.

 

I was looking at the double braided flex joint.

How long do you think they should be? 4" ? , 6" ? Weld on. I don't expect a lot of movement, vibration yes. These will be located in a horz section after making the 45' bend coming off the headers flange connection. This puts it along the side of the trans (pan/seam), so I may have to move it past the trans for clearance, before my H-pipe. All movement, if any should only be up and down. Since I used urethane bushing in the engine and trans it's going to be stiff, so very little.

 

Personally I would use 6 inch, over the long run it will be more forgiving than a short piece.