convert from X pipe to H pipe

[fgross2006]

I did a single to dual exhaust conversion last summer in my 84 5.0. Been having problems ever since.

I have stock shorty headers 3 inch mouth, FlowMaster X pipe 3 inch, pair of MagnaFlow mufflers with 3 inch openings and pair of MagnaFlow hi perf cats with 3 inch openings. lastly a pair of 2 1/2 inch walker tailpipes.

As you can see in this picture the driver side of the X pipe is lower then the other because the tranny linkage is right above it. That caused me to bottom out and crush the driver side cat.

Attachment 104329

Attachment 104330

I went to a muffler shop today to see if they could make adjustments and was told theres no room with the 3 inch X pipe I have. maybe with a 2 1/2 H pipe it could be made to work.

What's my options with this set up? My stock headers have 3 inch openings. How can I connect a 2 1/2 inch H pipe up to them? Was the stock original H pipe with a 2 1/2 pipe with a 3 inch connecting pipe?

I want to be able to keep all the above except the X pipe. I'd like an H pipe that will have enough room to weld on the hi flow cats and still clear the tranny linage.

What are my options?

Heres the shorty headers I have

Attachment 104331

Attachment 104332

[fgross2006]

what size is the stock H pipe connections? They have to mate to the stock headers I would imagine?

[Walking-Tall]

Those are stock "headers". Whether somebody told you and if they actually opened the holes up to "3 inch mouth" or not, unless the attaching studs were relocated (HIGHLY doubtful), they bolted to the stock exhaust pipes, as well as your 3" stuff, as well as any other 2-1/2" stuff....

[fgross2006]

Those are stock "headers". Whether somebody told you and if they actually opened the holes up to "3 inch mouth" or not, unless the attaching studs were relocated (HIGHLY doubtful), they bolted to the stock exhaust pipes, as well as your 3" stuff, as well as any other 2-1/2" stuff....

so whats my best option? Find a stock H pipe or get an aftermarket H and weld in my 2 hi flow cats? In any case I need to be sure I can clear the tranny linkage under the driver side with the cat.

Any pics of completed dual catted system would be helpful.

[bwguardian]

Good luck getting those headers back in place when you reinstall them. I had a pair of MAC units like that which were a pain even on the engine stand because they warp and there is nothing to keep the floating flanges in place that mount to the heads. I got rid of mine within a year and bought a pair of stainless Ford Racing units which have a heavy continuous flange to keep them in place. Most all headers advertise a 3" collector but even on my Ford Racing units I had to go in and clean up the welds on the insides of the collectors.

I additionally started out with a H-pipe unit...cannot remember the brand...and when I changed the headers went with a BBK X-pipe. I don't have cats and I do have the stock stainless tail pipes and have had no troubles with anything touching, scraping, or rubbing.

Don't know what to tell you on the headers, but for the H-pipe you should stay with the standard 2-1/2" unit. If you have the stock tail pipes they are smaller than the pipe on a standard H-pipe or X-pipe. I would locate the cats in a place where they will not be an issue.

[fgross2006]

I picked up this stock H pipe today with all 4 stock cats.

Attachment 104644

I plan to have the stock cats removed and my MagnaFlow cats welded in their place. The pre cats removed and straight pipe in their place.

I still need pipe and flange to bolt from the rear of the H to the muffler. I'm assuming that's a simple item Walker makes I can get in any parts store?

I found a repro of the stock air tube that goes from the Thermatic air check valve to the H pipe air induction tee. Im happy about that. Right now I have silicone tubing and its not great.

I know this H pipe will go right up in there since its stock Foxbody issue. But the surgery to remove/replace the cats can be delicate I assume.

Also, once I complete this conversion should I try to keep and sell the stock cats on ebay or craigslist? do they have any collectors interest?

[ashley roachclip]

They only have scrap value, but even cats are not bringing as mush money these days .

[Supersonic G.T.350]

Why cut the cats out unless there's something wrong with them?

[wraithracing]

Not to be rude, but seems like a HUGE waste of time, IMHO.

For your setup the stock H pipe will work just fine. Throw it on and leave it as is for the time being.

If you want to use your Magnaflow cats, then order either this https://lmr.com/item/SVE-5250X/sve-m...ad-x-pipe-8693 or this https://lmr.com/item/PYP-XFM10/86-93...Shorty-Headers and add your Magnaflows to either of those.

Then remove the OEM 4 cat H pipe and sell it to another Mustang/Fox owner and recoup some of your money. Good Luck!

[fgross2006]

Not to be rude, but seems like a HUGE waste of time, IMHO.

For your setup the stock H pipe will work just fine. Throw it on and leave it as is for the time being.

If you want to use your Magnaflow cats, then order either this https://lmr.com/item/SVE-5250X/sve-m...ad-x-pipe-8693 or this https://lmr.com/item/PYP-XFM10/86-93...Shorty-Headers and add your Magnaflows to either of those.

Then remove the OEM 4 cat H pipe and sell it to another Mustang/Fox owner and recoup some of your money. Good Luck!

I considered throwing it up as is but on the other hand I'd lose the 2 inch X pipe and 3 inch MagnaFlow hi flow cats for 4 stock cats that my 84 wasn't designed to run. I'd be losing a lot of power and flow. The only reason I'm switching the X to an H is to get a stock midpipe that fits perfect. I still want my hi flow cats in.

Those two pipes you link to are X pipes and may well put me back in the situation with insufficient space to make it work.

[bwguardian]

I considered throwing it up as is but on the other hand I'd lose the 2 inch X pipe and 3 inch MagnaFlow hi flow cats for 4 stock cats that my 84 wasn't designed to run. I'd be losing a lot of power and flow. The only reason I'm switching the X to an H is to get a stock midpipe that fits perfect. I still want my hi flow cats in.

Those two pipes you link to are X pipes and may well put me back in the situation with insufficient space to make it work.

The bottle neck in your exhaust system are the crimps in those stock headers.

[wraithracing]

From looking at your photos your issue is not whether or not the Mid pipe is an H pipe or an X pipe. Either should fit just fine if designed correctly and routed properly.

The stock H pipe is a 2.5" pipe although many report the actual diameter is less and closer to a 2 1/4" setup. Your issue is that you have a 3" mid pipe that appears to not fit properly due to the overall diameter and the actual routing of the pipes. This can be because of the X pipe itself or because of your stock style headers.

If for some reason you believe an H pipe will fit better than an X pipe here you go: https://lmr.com/item/SVE-5250B/1986-...ff-Road-H-Pipe

or this one: https://lmr.com/item/BBK-1507/86-93-...Shorty-Headers

Although I believe you will find that the H or X doesn't matter as that should be located behind the transmission mount and well out of the way of your current issue.

IMHO your issue is the same that many of us face when modifying these cars. You have a plethora or parts that may not have been designed to work with one another and installed in a car that never had dual exhaust. Once again when possible a system approach is often the best option because the parts are designed to work together and should with little or no modifications. I am just as guilty of mixing and matching parts as the next guy as budget, time constraints, etc. will do that. Heck my PC has a 91 5.0 with 95 aftermarket shortie headers and a BBK 87-93 midpipe on it with OEM 03/04 Cobra IRS exhaust. Does it all bolt up, clear, and work . . YES! Did it require tweaking and modifications . . . YES!!! When I redo the car, it will get a different/better setup, but that was what I had available at the time and it fit the budget.

IMHO the exhaust shop didn't want to mess with your setup and just told you it wouldn't work. I wouldn't use them again. As stated above your engine isn't anything super powerful, plus the stock restrictive headers don't help, so I would install the OEM H pipe and run it as is for now.

The issue you are going to have with your Magnaflows is that being 3" they are not going to fit any NON 3" H pipe without having to step up and step down the tubing if using a more standard 2.5" unit. When you make enough power to need the flow of a 3" cat then you will definitely want a 3" mid pipe and most likely will need/want long tube headers. Until that point, a 2.5" system will work just fine and not cause you any issues. Good luck!

[fgross2006]

From looking at your photos your issue is not whether or not the Mid pipe is an H pipe or an X pipe. Either should fit just fine if designed correctly and routed properly.

The stock H pipe is a 2.5" pipe although many report the actual diameter is less and closer to a 2 1/4" setup. Your issue is that you have a 3" mid pipe that appears to not fit properly due to the overall diameter and the actual routing of the pipes. This can be because of the X pipe itself or because of your stock style headers.

If for some reason you believe an H pipe will fit better than an X pipe here you go: https://lmr.com/item/SVE-5250B/1986-...ff-Road-H-Pipe

or this one: https://lmr.com/item/BBK-1507/86-93-...Shorty-Headers

Although I believe you will find that the H or X doesn't matter as that should be located behind the transmission mount and well out of the way of your current issue.

IMHO your issue is the same that many of us face when modifying these cars. You have a plethora or parts that may not have been designed to work with one another and installed in a car that never had dual exhaust. Once again when possible a system approach is often the best option because the parts are designed to work together and should with little or no modifications. I am just as guilty of mixing and matching parts as the next guy as budget, time constraints, etc. will do that. Heck my PC has a 91 5.0 with 95 aftermarket shortie headers and a BBK 87-93 midpipe on it with OEM 03/04 Cobra IRS exhaust. Does it all bolt up, clear, and work . . YES! Did it require tweaking and modifications . . . YES!!! When I redo the car, it will get a different/better setup, but that was what I had available at the time and it fit the budget.

IMHO the exhaust shop didn't want to mess with your setup and just told you it wouldn't work. I wouldn't use them again. As stated above your engine isn't anything super powerful, plus the stock restrictive headers don't help, so I would install the OEM H pipe and run it as is for now.

The issue you are going to have with your Magnaflows is that being 3" they are not going to fit any NON 3" H pipe without having to step up and step down the tubing if using a more standard 2.5" unit. When you make enough power to need the flow of a 3" cat then you will definitely want a 3" mid pipe and most likely will need/want long tube headers. Until that point, a 2.5" system will work just fine and not cause you any issues. Good luck!

Im just not to thrilled with having 4 cats when my car originally came with 1 cat. My regular mechanic says the stock bends in the stock cats are something he cant easily recreate. Im gonna stop by the local machine shop to see if they can do it.

I can throw the stock H pipe up there to see how it runs but Im sure Im gonna be disappointed with performance

[wraithracing]

Im just not to thrilled with having 4 cats when my car originally came with 1 cat. My regular mechanic says the stock bends in the stock cats are something he cant easily recreate. Im gonna stop by the local machine shop to see if they can do it.

I can throw the stock H pipe up there to see how it runs but Im sure Im gonna be disappointed with performance

Sounds like your mind is already made up. Good Luck

[fgross2006]

Sounds like your mind is already made up. Good Luck

I wanted to at least examine the possibilities of putting my cats on the stock H but 2 different muffler shops and local machine shop said not possible. So Ill most likely put the H on with the cats, for now, and see how it sounds and runs. If I don't notice a drastic loss of power I can leave it as is. I can always upgrade later on down the road with a better set up.

[bwguardian]

If it were me, I would be cutting those front 2 cats out and straightening the pipe bends for better flow in that area.

[homer302]

The bottle neck in your exhaust system are the crimps in those stock headers.

The bottle neck in this exact scenario would be the OEM CFI/auto combo. The wheezing OEM heads would struggle to fill up those 85 headers enough for the headers to be considered any sort of restriction. Also to the OP regarding the stock H pipe. You need the double hump crossmember to properly mount that. I am not certain if you have that or not. You may well, I just can't tell.

[84StangSVT]

The bottle neck in this exact scenario would be the OEM CFI/auto combo. The wheezing OEM heads would struggle to fill up those 85 headers enough for the headers to be considered any sort of restriction. Also to the OP regarding the stock H pipe. You need the double hump crossmember to properly mount that. I am not certain if you have that or not. You may well, I just can't tell.

It appears he does have the double hump already in place. I would have to agree with you on the CFI/Auto scenario. I don't see any reason that the stock H-Pipe and cats will hinder his performance any as he is stock anyways. I would personally slap the thing on and call it a day, as it will surely be less of a headache than trying to fit a huge pipe under there or paying out the nose to modify the H-pipe for no real performance gain.......unless of course the cats are shot.

[bwguardian]

The bottle neck in this exact scenario would be the OEM CFI/auto combo. The wheezing OEM heads would struggle to fill up those 85 headers enough for the headers to be considered any sort of restriction. Also to the OP regarding the stock H pipe. You need the double hump crossmember to properly mount that. I am not certain if you have that or not. You may well, I just can't tell.

Read my post again...I stated: "The bottle neck in your EXHAUST SYSTEM are the crimps in those stock headers.". The op is talking about the EXHAUST SYSTEM on his car.

[Walking-Tall]

You've now got a stock H-pipe with cats, with no cats alongside the transmission pan (which was a rather bone-headed move of whoever located them there, hence your shift linkage and ground clearance issues), so it should certainly bolt in and fit nice... and as others have stated, everything else you're working with is stock and no powerhouse needing 3" exhaust, so there's a pretty good chance you may end up feeling that the car actually performs better with this newly acquired factory h-pipe of yours.

[vintageracer]

What are we talking about here.

250HP on a GOOD day?

[fgross2006]

im still deciding what to do with this set up.

I did buy a stock H pipe with all 4 stock cats that would bolt right up but I hate to lose the performance I get from the Magnaflow cats.

Im thinking I should but a non catted H pipe that I can weld my Magnaflow cats into.

Looking at different aftermarket H pipes online they all look somewhat different in shape. Whats the closest aftermarket H pipe that matches the shape and configuration of the stock H? The stock H had 4 cats so I think I should be able to fit in 2 bullet cats into an H that's the same shape as stock

[fgross2006]

I have to get to this project sooner rather than later. once again the rubber insulators are breaking because the tail pips have too much tension. Im rattling when I hit bumps, the driver side tailpipe is hitting the edge of the gas tank.

I picked up a stock H pipe with 4 original cats but Im really not too enthused to use it. I really want to get a good aftermarket H pipe that I can weld a pair of MagnaFlow hi performance cats into. Has anyone done something like this? Would this BBK H pipe work good for this purpose? Im trying to see where Id cut into it to get best clearance.

Also I notice on my stock H and the after market H that the back end where the mufflers would connect have flanges. That looks like I'd need 2 mating flanged pipes to mount the mufflers to. The X pipe I have now has mufflers welded on both sides.

[Mustang-junky]

I'm not sure if you can mail order hi-performance converters in NYS anymore. Guess you could buy them out of state and bring them in yourself though. New converter laws mean stock replacement or CARB certified for 1993 and newer. I know yours is older, but sellers don't know that. Maybe I'm wrong?

Jess

[fgross2006]

I'm not sure if you can mail order hi-performance converters in NYS anymore. Guess you could buy them out of state and bring them in yourself though. New converter laws mean stock replacement or CARB certified for 1993 and newer. I know yours is older, but sellers don't know that. Maybe I'm wrong?

Jess

I already have a pair of MagnaFlow cats. Perfectly legal in NY.

The issue is finding a suitable H pipe I can cut and weld a pair of bullet cats onto and still have clearance.

These cats with a Flowmaster X pipe didn't work out