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post #1 of 7 (permalink) Old 01-29-2008, 01:24 PM Thread Starter
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Modifying mustang longtubes

I wanted longtubes for my mark viii instead of midlengths, and I wanted to do my headers on a budget also. I just ordered a set of painted flowtech 96 cobra longtubes from jegs for 290 bucks, which includes all mouting bolts, gaskets, and 02 extensions.

I know that before there were midlengths, mark viii guys used to modify cobra headers for their cars, and I think I remember some 4.6 thunderbird guys doing the same things with GT headers. My questions is about the actual modification that needs to be done to the drivers side for the steering shaft.

These headers on the drivers side are divided up into 2 parts for the installation, you install the rear 2 primaries, then run the steering shaft, then bolt up the other 2 primaries and then slip the collector on kind of like bassani headers.

Through my research, I have found that the passenger side typically fits without too much drama, and that the drivers side typically only needs 2 of the primary tubes modified to clear the steering shaft.

Would anyone happen to remember which tubes were typically modified and how? My search didnt turn up any pictures. I am hoping to do my longtubes in march, along with a full 2.5 inch X-pipe with twin dynomax bullets, and muffler tips out back that are like the ones that are sold by a couple of vendors on here, but off brand. I am hoping it wont drone with the X, the bullets, and the rear mounted mufflers, and I am hoping to pick up a 25 rwhp increase with the full exhaust.
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post #2 of 7 (permalink) Old 01-29-2008, 10:59 PM
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there has been little talk from time to time on this subject on here, and when it gets brought up it gets shot down my the guys with alot of knowledge on the subject of mn12s real fast. i beleive the general consensus is that your idea was tried and talked about alot but never completed. there is supposed to be some serious floor panel clearance issues. if you could copy and paste your research onto this forum so we can see what your talking about? maybe you alone have wandered across something easily done that all these guys havent noticed.

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post #3 of 7 (permalink) Old 01-30-2008, 08:37 AM Thread Starter
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Most of my research is mark viii based, but I know that 3 of the faster N/A marks and a couple of the supercharged marks modified MAC longtube headers. Search Modified headers on , and they should come up with what you need.
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post #4 of 7 (permalink) Old 01-30-2008, 09:47 AM
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I have 2 pair of MAC longtubes for Mustangs, perhaps we can do a test fit on JamesD car since his motor is out.

Edit - my bad, I have 2V longtubes but maybe should take a quick look anyway unless someone has already tried.
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post #5 of 7 (permalink) Old 01-30-2008, 11:49 AM
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Originally Posted by lightningvic View Post
... I am hoping to pick up a 25 rwhp increase with the full exhaust.

i doubt that is possible with just exhaust on the marks...the stock exhaust on the mark isnt too restrictive for what air it pulls around and you'll find out that the dohc's actually do a tad too good on the air and exhaust side vs. the displacement of the engine...reason the IMRCs on the intake are there....that is what i remember what i read a while ago and what im basically getting at is that 25 might be a high goal for just exhaust without any supporting mods...

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post #6 of 7 (permalink) Old 01-30-2008, 12:40 PM
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I really don't think enough people have done this to be able to tell you exactly which tubes need to be modified. Plus every brand header is done a different way, so what works on one brand might not work on another. The easiest way to figure out what you will need to do is going to be to remove the steering shaft, then install the headers, make your clearance for the floor if needed, and then start to re-install the steering shaft and see where it is hitting and how bad.

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post #7 of 7 (permalink) Old 01-30-2008, 08:18 PM
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KDanner also mentioned that MAC longtubes almost fit.....i think he said the problematic side is naturally the driver's maybe MAC is the way to go for those who can/will custom fab up some stuff along the way to make them work

Last edited by guitar maestro; 01-30-2008 at 08:33 PM.
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