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I didn't want to put this post in the "tech" area because its not a technical problem. Just need some opinions. I have a 67 cougar with a 92 ford mustang engine efi with bbk headers. I bought a x-pipe (no cats) and bought the 17281 american thunder flowmaster exhaust kit (comes with hpipe no cats). The kit is hung except this problem. I will say since I did the ford explorer rear end swap in it, I was surprised I do not have to shift the exhast over at all. There is plenty of room there. Well I knew there would be welding to do. I have 2 options.....

The bbk xpipe came in 3 pieces. the actual x pipe itself and 2 pieces that go from the headers to the pipe (kind of like a down pipe). The h-pipe has the same set up except no flanges.

1) I can take them "down pipes" and weld it onto the H-pipe provided by flowmasters kit and the rest of kit fall right in place.

2) I can put on the bbk x pipe, hang the kit....BUT, the intermediate pipes (go from the muffler to the h pipe) are too short. So, I would have to get 2 new pieces of pipe made to work. I would also have to cut the back flanges so I can but them together and weld.

What are you opinions??? I have the skills to do both. I have built my engine with edelbrock up, stroked it to 347 with scat. I have dumped a lot of money into and want to get as much horsepower possible. What produces more HP, the h pipe with no cats or the x pipe with no cats? I googled that and it seems to me a lot of 16 year old kids were making up stories! Thanks for all the help!!!!!
 

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"cats" or catalytic converters are restrictive. Unless you need them for your engine feedback/computer, leave'm off.
 

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Well, it's actually going to vary a bit depending on where your motor develops peak torque....no "easy" answer. The old school method to make the H-pipe fit in the peak spot was to run open collectors on your headers (painted the day you are going to the track), and make a few hard runs to see where the paint burns off. That is where you put your h-pipe and the junction where the heat trails off because it's where the back pressure will equalize the best. Once you put mufflers on, it's going to vary some too, depending on how restrictive they are --- most of them are not very much these days. X-pipes tend to have the benefit of blending the pressure at a smoother angle, but it's tougher to hit the sweet spot until you know where pressure is wanting to equalize if you just slap 'em on.
 
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