So, building motor mounts to stuff a ls1 into a 240sx seemed like a challenge, but it was actually a breeze compared to building headers and attempting to make the tubes equal length. I started with a 1-3/4" OD long tube header kit from Summit Racing, a set of 3/8" LS1 flanges and two 180 degree J-bends from Jegs. The long tube header kit has tubes that are bent for a small block, probably to go in something pretty large, like a monster truck, because when I placed one of the pipes in the 240 it hung under the car about 2". For this project I'm not sure if the kit was the way to go, but for about $100, after cutting the tubes up, I had a lot of bends to work with. Also I was unimpressed by the fit of the collectors so I purchased a set of Megs formed merge collectors and merge bullets, these are nice pieces.
Megs Merge Bullets after welding.
I was happy that I had called them they pointed me in the right direction for my power goals and my usage of the car. As a result I am using smaller than typical collectors and going with a 2-1/2", the same size as my Y-pipe. But with the tighter collectors I am going to have to make sure to have a good equal length design for my header tubes.
I made and adjustable collector holder to hold the header collector in position.
My first length attempt was 32" with the collector just behind the firewall, to maximize ground clearance, it worked great for the two cylinders to the front of the engine, but not so well when it came to the back two, I had to pick one or the other to make the 32" length, then the one that didn't get the length was going to be 4-5 inches shorter which just wasn't going to work. So I went back to the drawing board and came up with some creative tube arrangement to shorten all of the tubes to 28" the shorter end of the recommended length from cone engineering.
Notice the front most tube, its tucked as tight to the block as I could get it and actually enters the collector above the next tube behind it to make it possible to make these headers equal length.
I decided to tuck the front most tube in very close to the block and take the straightest path possible towards the collector, inserting it into the upper opening (rather than the lower opening where it would typically go), tucking the second tube from the front underneath it. With this tangled tube arrangement, I was able to get the first three cylinders within 1/2" of length of each other and the last one within 2", this is not perfect equal length, but I think it will do. I could have squeezed a little more length to get it closer to the 28" goal, but I would have had to have much more aggressive angles, which didn't seem worth it in terms of loss of flow.
Front View
Here's the underside view, there's another new tool under there, an adjustable V-channeled (angle iron) tube tube stand. Between this and the collector holder these are some massively helpful tools.
I wanted to run all the tubes to one side or the other of the steering shaft, but the collectors wouldn't fit through and it wasn't working for the equal length thing either. I ended up running the front two cylinders inboard, and the rear two outboard kind of like the passenger side.
Both sides outside of the car.
See the steering gap, I'm hoping its enough, but if I have any problems I'm just going to stiffer motor mounts.
I did the final test fit on the headers after the guys at Advanced Chassis welded the tubes to the flanges, I couldn't be too careful before ceramic coating. As always they did a great job and everything came out perfect. They even modified a tube slightly for increased steering clearance. For the ceramic coating I chose a color called blue titanium. Pictures are hard to do the color justice, its a matte charcoal grey color with a little blue metallic, I really like its clean, not too flashy look.
