Q:I know H-pipes (straight cross-overs) are doable, and that aftermarket kits are out there, but I was thinking about X-pipes. They build more HP, they scavenge better, and they are more efficient = better mileage. I was just wondering about clearance...anyone know?
A:I'm fabbing my own on my '70 RoadRunner, it's all the same underneath . I'm using Hooker Super Comp Plus headers with 1 7/8" primaries going to 3" collector and 3" pipe to a pair of Dynomax mufflers, 3" in and out, and dumping in front of the rear axle. Everything is going to be welded except the mufflers. I got the center X fabbed and welded all the way to the collectors, but I had to order two more 45's to complete the job. The tube on the driver's side has to be fabbed to go around and thru the crossmember so it would shoot straight back and parralel to the passenger side. This has to be done if you're using 45 degree mandrel bends to make the geometry work out. I don't have a picture of it, but if you would like, I can snap one tomorrow and post it.
OK here goes....#1 is 20" center to center, #2 is 27 3/8" from flange to center of X, #3 is 13 1/4" from flange to where the 45's start, #4 is 15 1/2" from CENTER to CENTER(it's very difficult to measure from inside to inside on round tubing and get an accurate measurement), #5 is 90 degrees, #6 is 90 degrees, A1 & A2 are cut to fit from 45's(see text below), B1 & B2 are full 45's with nothing trimmed from them. I'm using Walker part #41428-3" 45 degree bends(6 req'd). A1 & A2 are cut trimming both ends till you get a good fit around the crossmember. I done this by bolting the collectors to the flanges and using the "Ricki-stover" method of fitting. "Ricki-stover" is a reference to fitting pipe by the seat of your pants till you get the fit you want(if it will work for high pressure ammonia and hazardous chemicals, it'll work for this). I am a pipewelder/pipefitter, and have run into situations where the mathematical formulas don't work, so I had to improvise. Hence my nickname of Ricki-stover, I can fit "stovepipe" with the best of them!!! I would like to point out that I had to cut the collector for the driver side so that the measurement from flange to cut is 3/4"(see pic). Once the collectors were bolted on the headers, I started fitting and tacking everything together under the car. I was working alone and took my time with the fitting, took a couple of tries to get around the crossmember the way I wanted. Once everything was fitted, I tacked a spacer bar between the collectors to maintain dimensions during welding(VERY important)!! I'd also like to note that the flanges on the HEADER are NOT square with the world once they are installed on the motor, that's why everything was fit under the car before welding. I'm still waiting for two more 45's to show up before I can finish, and I'll get a pic of the whole thing from the collectors to the mufflers before I install it. You might want to go to a welding supply store a purchase a pipe "wrap-a-round", makes straight cuts for butt welding pipe very easy, as long as you make a straight cut. It can also be used to make your cut lines for the saddles at the X, if you're familiar with pipefitting methods.
Looks great...I gotta have those pipes on mine! I'm going to attempt to fabricate with some help from a pipe fitter...we'll see.
Hate to ask, but could you take 3 final measurements?
The dimensions are as follows, #5 is 4 1/2" center to center, #6 is 17 5/8" from center of X to the ends of the 45's where the mufflers go on(for a total length of 45"), and #7 is 21" center to center. Keep in mind that I fit this up to use my particular mufflers. Depending on what mufflers and type of 45 bends you use, you might have to alter some of these dimensions to accomidate your components. But I hope this works for a good place to start, don't be shy about making changes that fit your needs. Good luck, Rick
