JMortensen Posted August 30, 2013 Share Posted August 30, 2013 Just starting this to document how I'm doing side pipes on my autox project. Wanted side pipes so that I could do a flat undertray and looked at a couple different setups which consisted of shorty headers that had a J bend off of them with a 90 after that. They went through the frame rail right next to the TC boxes, which was something I didn't want to mess with because I'd already removed those boxes and made different TC mounts for my chassis. tube80z turned me on to Schoenfeld's IMCA modified headers: http://www.schoenfeldheaders.com/LS1-IMCAMOD.htm and I was tempted to buy ones with the collectors that point down, but I really don't know where they would end up so I ended up with the shorter ones that just have a plain collector at the bottom of that page. I told them I wasn't sure about spacing and asked if they would send the collectors loose, which they did for me. Just received them yesterday and bolted them up to take a look.I wasn't expecting this, but they also sent me some slip fit brackets so that I could just use the collectors that way rather than welding them on. Never messed with header construction before, but it looks like there would be big gaps between the pipes and the collector so not sure if slip fit on these is a good idea. Don't know how they normally get welded for that matter. Maybe this is SOP in cheap circle track header land. They are going to clear my custom motor mounts which mount to brackets on top of the frame rail. That means that the headers will go over the frame rail. This is a very nice surprise, I'm glad I won't have to mess around with notching the frame or any of that BS. These headers are thin and light, but I think that means that they'd die a quick death on a street car. For my trailered race car, not so big a deal. This is the second part I've gotten recently (Kevko oil pan was the other one) that was painted so badly I wish they hadn't painted it at all. Terrible paint job on these headers. Next step is to drop the motor in the car, get the motor mounts welded in, and cut holes in the fenders for the exhaust pipes. This is a cool little product that I'll add to these headers too. Called an "exhaust bullet" goes in the collector and smooths the flow. I saw some Cobra side pipe testing where they had added these and gained 10+ hp on a 500 hp engine if I recall. Might just spring for their whole collector kit and weld it up myself. Looks like real quality DIY stuff. http://www.coneeng.com/collector_components.html Quote Link to comment Share on other sites More sharing options...
JMortensen Posted October 24, 2014 Author Share Posted October 24, 2014 Well, this didn't turn out as expected... The IMCA headers outlet was too far forward, so the collector was positioned just behind the strut. Basically unusable. I ended up cutting the primaries off and using the flanges. Bought a box of bends from Schoenfeld, which is really just that, a random box full of what look to be screw ups from their production. Cheap though. I did end up with the merge collectors, and I also bought the stuff to make mufflers from them as well. I used 60% closed stainless steel perforated tube for the center and bought some fiberglass packing to stuff in there. They've been talking about really seriously cutting the db allowance at our local autoxes, so I aped the Burns Stainless muffler which has angle iron in the flow path, essentially making a bullet chamber muffler. I welded stainless angle about 1/3 and 2/3 way through at 90 degrees to each other. Hopefully that will be enough to get me under the sound limits. For tips I took a ss U bend and cut it to make 2 turn downs. I used V bands at all the joints, that way I can easily disassemble if needed and if it's still too loud I can bolt another muffler behind the first one. There is still a lot of room on the side for another muffler. For the header fab I started with the collector, and tack welded 4 90 degree bends into it. Then I welded on a V band and bolted the collector to the muffler, and the positioned it so that it would clear the tire and the car at full lock. I did have to trim the front of the rockers a bit. This is where about 5 layers of sheet metal come together, so I was careful to weld it back up properly. At this point I needed to figure out how the tubes would be routed, so I took some 1.5" foam cylinders and shoved a 1/8" welding rod in each, then bent them to mimic the pipes and plugged them into the header flange. Once I had a basic idea of where they would go, I went back and worked from the flange back on each tube until it was tacked, cutting and fitting and tacking and removing and cutting and fitting and tacking until I was satisfied. Of the 8 primaries I tacked in the car, only one of them was actually good enough when they came off the car. Once I removed the header and flipped them over, every single "tight fit" joint that I had made turned out to need a little massaging to get it right. Final job was the exhaust mounts for the side of the car. Just finished these yesterday, not sure if they'll do the job or not, but I guess I'll find out. Seems one of the problems with cobra kits is they hard mount the side pipes and when the exhaust gets hot and expands it puts a lot of pressure on the rocker of the car, cracking the fiberglass. They have some rubber mounts that have a 7 or 8 inch long arm with rubber on the inside end, and that didn't seem like it did anything at all. After seeing a real Super 7 Lotus with a spring wrapped AROUND the muffler and to a steel pedestal, I came up with something similar. I didn't want to wrap a spring around the muffler because I'm going to put heat shields on it, so I used a short spring and welded a pedestal/spring hanger to the rocker on each side. I couldn't get the spring directly straight, so I opted to have it pull up slightly on the muffler instead of down. The front primaries are really long and the rears are much shorter, and in retrospect I think I should have gone bigger on the primary size (did 1 5/8"). We'll see how it works out, but I'm thinking it won't hurt me too badly at autox rpms, and more importantly, I'll be able to set the car down REALLY low and not scrape the exhaust. Although they look really low, the headers are actually about an inch and a half higher than the frame rails under the car. Quote Link to comment Share on other sites More sharing options...
The Infidel Posted October 24, 2014 Share Posted October 24, 2014 Can't wait to see and hear the finished results. Quote Link to comment Share on other sites More sharing options...
RebekahsZ Posted October 24, 2014 Share Posted October 24, 2014 Looks GREAT! You better wear socks.... Quote Link to comment Share on other sites More sharing options...
heavy85 Posted December 28, 2014 Share Posted December 28, 2014 Considering switching to side pipes myself to get long tube and ground clearance. It looks like the original circle track headers would of worked if you cut them back, added 90 elbows to point them down and back, then added the collector and a single pipe over to the mufflers. Did you try this or think it could work? Quote Link to comment Share on other sites More sharing options...
JMortensen Posted December 28, 2014 Author Share Posted December 28, 2014 Considering switching to side pipes myself to get long tube and ground clearance. It looks like the original circle track headers would of worked if you cut them back, added 90 elbows to point them down and back, then added the collector and a single pipe over to the mufflers. Did you try this or think it could work? No, don't think you could use the headers as is. Even if you cut the tubes as far back as possible and put a collector on and then added a 90 to turn it away from the wheel, just wasn't going to happen. The collector would point out just behind the strut on my car with the engine moved back about 1.5" from the JCI position. If I had more resources at my disposal I would have done one of two things: 1. Make the rear cylinder primaries twist around the fronts, so that the front cylinder primaries had the long route around the corner and out to the side of the car or 2. Put the collector inside the wheel well and then run a 2.5" tube around the corner. Either would have made the primary length more equal. As it is I think what I have will work fine and there is a theoretical advantage to the longer tube primaries over doing #2, but there is SUCH a large difference in the length of cyl # 1 and 2 vs 7 and 8 that I wonder if #2 would have been the better way to go even with the disparity. Also, being that I am using a smaller 5.3 I went with smaller tubing. I'd probably bump it up to a 3" merge collector for an LS1 and been wondering about going bigger yet for anything larger. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted December 28, 2014 Author Share Posted December 28, 2014 Quite literally woke up this morning saying out loud "Tri-Y". If you did a Tri-Y you could have 2 2.5" tubes round the corner on top of each other and get your long primaries and the rest of them would stay about the same length. Build cost goes up because you'd need more Y's and not sure if they have merge collectors for Tri-Y's or if you need a particular length ratio for the first Y and the second, etc, but having done the 4-1 I think it might be a good idea to check it out. Quote Link to comment Share on other sites More sharing options...
heavy85 Posted December 28, 2014 Share Posted December 28, 2014 No, don't think you could use the headers as is. Even if you cut the tubes as far back as possible and put a collector on and then added a 90 to turn it away from the wheel, just wasn't going to happen. The collector would point out just behind the strut on my car with the engine moved back about 1.5" from the JCI position. I meant cut back, add 90 elbows first, then add collector - would that work? Rotate the 90s so the collector pointed angled down and back. Dont know what you mean about tri-y when there are only 4 cyl to work with? Quote Link to comment Share on other sites More sharing options...
JMortensen Posted December 28, 2014 Author Share Posted December 28, 2014 Tri-Ys are a 4 cyl design. 4 cyl merge into 2 Ys, then they merge in a 3rd Y. After doing this I'd suggest that fixing the Imca header would be more difficult than building one the way you want it. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted December 29, 2014 Author Share Posted December 29, 2014 (edited) Was out in the shop today and had a look at my Miata header which is out as the engine gets rebuilt. It is a Tri-Y and the first two primaries might be shorter than the second length of the Y. This is an OBX header which is a pretty straight rip off of the Jackson Racing header, a well respected piece among Miata racers. Edited December 29, 2014 by JMortensen Quote Link to comment Share on other sites More sharing options...
JMortensen Posted December 29, 2014 Author Share Posted December 29, 2014 (edited) Was out in the shop today and had a look at my Miata header which is out as the engine gets rebuilt. It is a Tri-Y and the first two primaries might be shorter than the second length of the Y. This is an OBX header which is a pretty straight rip off of the Jackson Racing header, a well respected piece among Miata racers. EDIT-- here's another shot of a new Jackson racing part: Edited December 29, 2014 by JMortensen Quote Link to comment Share on other sites More sharing options...
We Bad Posted January 3, 2015 Share Posted January 3, 2015 http://hotrodenginetech.com/pipemax_header_design_software/ If you are curious to see how your unequal length primaries compare to equal-length primaries, or how long the primaries should be, or what the optimum primary diameter should be you can try this software. In my opinion it is cheap entertainment compared with the time and money you will spend fabricating such headers. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted January 5, 2015 Author Share Posted January 5, 2015 How would you feel about running some scenarios for us? Quote Link to comment Share on other sites More sharing options...
We Bad Posted January 7, 2015 Share Posted January 7, 2015 PM sent Quote Link to comment Share on other sites More sharing options...
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