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Discussion Starter #1
Husk and others w/ long tubes, are any of you running fuel injection with your long tubes ? I just bought the Mac longtubes, and want to get them ready. My goal is to check the fit, and modify as needed, THEN have them ceramic coated inside and out so they'll last. First I have to extend or modify the collecters, I have an AOD to use. I also want to check clutch shaft fit, as I want to swap to Tremec 5 spd when budget allows. But I also want to be able to run the throttle body fuel injectors I have. So I'll weld in a couple of bungs and plug them for now. But where should you run the O2 sensors with long tubes ? Should I plan on them straight up in middle of collector ? Straight out sideways ? Open to suggestion, and wondering what others W/ FI have already done. Regular readers know I have recently retired. Engines are easy for me, but the headers and O2 senders and stuff are things I didn't have to deal with. What says you ? LSG
 

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As part of checking the fit, check to see where it will be best to mount the O2 sensors. I am guessing straight out will be the best as your should have ample room between the header and the frame rail (I do, but I have different headers).

Don't rule out a clutch cable or hydraulic system. I have had not issues with a clutch cable and am especially confident now that I have ceramic coated headers. The heat is WAY down.
 

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You want to install your O2 sensors in the collector or approximately 24" +/- from the primary tubes. 12 o'clock is ideal but anywhere between 9 and 3 o'clock is acceptable. You do not want to install the sensor horizontal or underneath as water will have detrimental effects on the sensor.
 
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Discussion Starter #4
O2 sensors

Lato, I have always run carb'd stuff before. How far above the collectors will the sensors protrude ? LSG
 

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I don't know which Throttle body injection system you'll be running, but having just installed a Sniper and in positioning the O2 sensor, I double checked Holley's recommendation. In their instruction, it reads: "If you have long tube headers, mount the sensor approximately 6-10” after the collector. You must have at least 18” of exhaust pipe after the sensor." It also states that it should be mounted in the upper half, at least 10* up from horizontal.
Other systems may be different, but if they are all similar, the bung placement will not affect your headers.
 

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This is a wide-band sensor from a Fitech system. The body (that would be sticking out of the exhaust pipe) is 2" with a fairly hard plastic strain protector that doesn't want to bend beyond it. 3"+ to fit this assembly into a probable tight area.
 

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I have JBA long tube headers with a Fitech TB fuel injection. I purchased the Summit brand SS collectors and welded a O2 bung into them per the Fitech instruction. The collectors were very reasonably priced. If you use a clamp between the collector and the exhaust pipe you can rotate the O2 sensor to wherever you need it to fit and when you put in your T5 you can rotate it to a new position if needed. The O2 sensor is in the passenger side tube, or in this picture its the top tube!
 

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I mounted my O2 sensor 6" after the collector and 6" before the crossover pipe at 11:00 o'clock on the drivers side when I put headers on this summer. My car now idles annoyingly smooth! It always idled like crap with the O2 sensor mounted 4" after the HiPo manifold as recommended by FiTech.
 

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@LSG, I'm assuming you've seen pictures I've posted along with comments. A quick wrap up. I had a interference issue with the Z bar shaft on one tube. I forget which cyl, #7 I think. No big deal. Also one tube on each side came close to the frame. I just flattened it out slightly for a little extra room. Since each tube has it's own flange I think when I was "adjusting" a tube I tweaked one of tubes and couldn't get a bolt started. I had to test fit on another head and correct the issue. I'm pretty certain it was my own doing but it doesn't hurt to check anyway. I had plenty of room for the clutch linkage otherwise and no issues with the starter.

If you're not aware, MAC sells the rest of the exhaust system to go with it. Either the regular turn downs or GT through the valance. It's all 2.5" mandrel bent galvanized pipe. Everything fit very well EXCEPT the short pipes from the H pipe to mufflers. I spent pretty much a full day on my back under the car on jack stands trying to make the mufflers fit. I thought they gave me 2 left hand side or something. I called their tech service. The guy acknowledged the issue. He said they made them "universal". That was puzzling to me because they spent enough time in making everything else fit pretty well and to cheap out on a 18" or so long pipe was odd. Oh I don't like or recommend their requirements on a muffler. They want center inlet, offset outlet. That center inlet puts the mufflers close to the driveshaft. In my case I have a Explorer aluminum shaft that is larger. Anyway I had to cut and reclock and weld those short pipes to get everything to fit.

These headers will fit PS without a drop bracket. While I don't have efi I do have a wide band O2 sensor. The bung has to be welded in slightly above horizontal. This is so condensation doesn't collect on the sensor. You really don't have too many options where to mount it either. The floor plan and trans cross member and everything else pretty much dictates where it is going. Feel free to ask me anything.
 

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Discussion Starter #10
headers & O2

Husk, do you have any pictures of how your O2 is mounted ? I still have to modify the collectors before anything esle. Somewhere I saw someones picture of how the collector flange hits the pan of an AOD. I don't really want an AOD, but I have one, and don't have a Tremec yet. I really think I need the overdrive. Car has C4 now. Clutch pedal is there, ready & waiting for someday. I need new exhaust, and have been looking at everyones pics. I chose the Mac's from looking at yours and others with this # because I wanted to avoid the PS drop bracket if I could, don't think I'll run P heads, but it is nice to have the option.
I kinda knew that Mac had other stuff, but don't like the ball/socket collectors. It necks them down to 2 & 1/2, and its just not what I'm used to. So I thought I would test fit, add O2 bungs, dimple where needed and then extend the collectors straight back and do a normal 3 bolt 3 inch connection. Or maybe no bolts at all, my exhaust guy has some shrink fit things he has done very well with. He has put them on several header cars, included the shop owners car of where I retired from.
I thought I would go 3 inch to my offset in / center out mufflers and then over the axle and out through the rear valence cutouts. I know its a pain, and will cost me to have it done, but I have seen it fit other 69s, no reason I can't have it. The larger pipes give a deeper note than the 2 & 1/2s, and I like that.

Thanks to all for pictures ! Y'all have been VERY helpful ! Now I just have to get back @ it ! LSG
 
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