Tired of dealing with cracked jpipes - look for reliable, compact header solution

[TallerMike]

We've been plagued by cracking jpipes for the last 5 years and I'm out of fixes and looking for a permanent solution. Looking for help to know which will be most reliable, and most likely to fit with the footbox customizations we've made.

Specs:

MK4 complete kit
2014 Coyote
Ceramic coated BBK shorty headers from the complete kit with the 2-bolt pivot flange
Stainless jpipes with the 2-bolt pivot flange
Mild steel sidepipes, modded by Gas-N with quiet pipes - ceramic coated
Ceramic coated heat shield
jpipe hangers
Single bolt on Factory Five exhaust hangers; rubber isolator wrapped in band clamp to reduce bounce


History: The original jpipes cracked within the first few hundred miles. After having them welded at a local shop, we installed jpipe hangers and thought the problem was solved. Over the next few years, they cracked at least once a year. We ended up buying 2 more SETS (6 total jpipes) to confirm that it wasn't the welding which was weakening and encouraging the cracking. I've rewelded some of them so many times the heat cycles have caused the pivot flange to no longer be round. We tried adjusting the jpipe hangers, and most recently added hose clamps around the rubber isolators on the factory exhaust hangers. While this reduced the bouncing when hitting bumps, it wasn't enough to prevent them from cracking again. I'm tired of smelling like exhaust from the leaks and pulling them off every 6 months to weld them up again.

My wife and I are both tall, so we expanded the passenger footbox forward to match the length of the driver's side (it's not close to the jpipe so I assume that 4-pipe headers won't touch here). We also expanded the width of the boxes so that they are closer to the BBK shorty headers. I really don't want to cut into the boxes since we've sealed them up with Lizard Skin and it would be a pain. Hoping that one of the manufacturers (FFR?) followed the BBK header design coming out the engine to keep the pipes tight to the engine.

Ask: Looking for a replacement header solution which will be strong and have the best chance fitting in the narrowed space caused by expanding the foot boxes.

Options I've seen:

FFR - 16796 - Headers: 5.0L Coyote stainless steel 4-port full length with ball flange collector (https://thefactoryfiveforum.com/showthread.php?44571-For-Sale-Factory-Five-MKIV-5-0L-Gen-2-Coyote-Headers-amp-Stainless-Steel-Sidepipes&highlight=headers)
FFR - 16790 - Headers: 5.0L Coyote stainless steel 4-port full length with catalytic converters
FFR - Old style - 3rd generation Headers: 5.0L Coyote stainless steel 4-port full length without ball flange collector (https://www.ffcars.com/threads/ffr-stainless-gen-3-coyote-full-length-headers-for-mk4-roadsters-or-gen-3-coupes-with-4-into-2-side-pipes.644811/)
Gas-n - Coyote Long Tube Stainless Steel Headers (https://www.gas-n.com/products/coyote-long-tube-headers)
GP Headers - Factory Five Coyote Headers (https://www.gpheaders.com/shop/cobra-kit-car-headers/factory-five-coyote-header/)
Stainless Headers - Headers For A Cobra Kit Car With A Ford Coyote (https://www.stainlessheaders.com/coyote)


Questions:

FFR-16790 with the catalytic converters; will these reduce exhaust smells even more? If they go bad, is there any way to replace them short of buying who new headers?
Any with flexible ball collectors, how stable are they? The jpipes ball connector required tightening to get it to seal and not slowly droop, possibly from the bent jpipe cups, and ended up developing ridges which prevents a solid seal now.
For those without flexible ball collectors, how do you deal with getting the angles just right? Is everyone just using the shims? Is any manufacturer better aligned?
Which design/manufacturer/material (mild steel vs stainless) is strongest so that I don't ever have to deal with this again?
Which manufacturer has the most compact design coming out of the engine, mostly closely matches the BBK shorty headers? Can someone measure their headers from the engine surface to how far the pipes stick out at the first and last ports on the passenger and driver's sides? I borrowed a set of FFR-16790 from a neighbor to try measuring fit.

[Cutter 54]

https://eziil.com/steel-strengths

Regarding steel strength you may want to review some published data (see above address) on elasticity, thermal expansion, yield strength, etc. when considering header or j-pipe material. While stainless has many advantages, it is not the strongest of metals. But above the issue of strength, consider some way to reduce movement such as the "anti-droop" brackets Jeff Kleiner designed for full length headers. I think excess movement is your problem.

[michael everson]

Your best option is the FFR ball flange headers. Assuming they will still fit. Most likely thought you might need to have a custom set of headers made at a shop with your car present. You dont say where your from, but in MA I use Tubular automotive.
I would recommend steel over stainless for strength.
Mike

[TallerMike]

But above the issue of strength, consider some way to reduce movement such as the "anti-droop" brackets Jeff Kleiner designed for full length headers. I think excess movement is your problem.

Do you have a link to this? I searched and can’t find anything. I have hangers very similar to the Dark Water Customs hope hanger setup and they still crack. Agreed that its movement that’s causing stress on the metal, but I’m at a loss for further preventing movement.

[TallerMike]

Your best option is the FFR ball flange headers. Assuming they will still fit. Most likely thought you might need to have a custom set of headers made at a shop with your car present. You dont say where your from, but in MA I use Tubular automotive.
I would recommend steel over stainless for strength.
Mike

I’ve borrowed a pair of the FFR headers to measure with, but they don’t have the ball flange. Are you suggesting the ball flange because of fitment issues?

I’m in NC

[michael everson]

no just because they give you the most adjustment for side pipe fit.
Mike

[Lidodrip]

My only experience is with a Coyote, the FFR 16790 headers, and GasN stainless steel touring pipes with heat shields. I have about 700 miles on this setup and have been pleased - no issues with excessive heat, pipe movement, or obvious stress. The headers are well made and there is a good amount of adjustability with the side pipes. I did need to use some wedges from Breeze to get the pipes to fit/align perfectly. I don’t know if the catalytic converter is replaceable. I would do this setup again.

James

[Jeff Kleiner]

Moot point now but you might have avoided the J-Pipe cracking had you incorporated some front hangers. I've made a few sets on customer builds, both for cars with the J-Pipes as well as the ball flange which is sometimes difficult to keep from moving without the additional support:

https://thefactoryfiveforum.com/attachment.php?attachmentid=181943&d=1679580697

https://thefactoryfiveforum.com/attachment.php?attachmentid=181945&d=1679580735

It's all just a few bucks worth of hardware store turnbuckles, nuts and bolts and a generic Mustang style double donut rubber tailpipe hanger.

Jeff

[TallerMike]

Moot point now but you might have avoided the J-Pipe cracking had you incorporated some front hangers. I've made a few sets on customer builds, both for cars with the J-Pipes as well as the ball flange which is sometimes difficult to keep from moving without the additional support
Jeff

Thanks, Jeff - I’ve had a nearly identical setup to this for a few years now and it reduced the cracking but didn’t eliminate it. Previously the cracks would nearly separate the pipes with wide open gashes. Now the cracks are tiny hairline fractures, but they keep coming back.

[J R Jones]

Mike, You should consider the contribution of metal fatigue to your problem. That is not just stress but a vibration at some frequency(s) that cracks the metal over time.
It is possible that with your engine mounts and your RPM operating range you have a sympathetic frequency/amplitude that your exhaust does not tolerate.
An engine mount change could help or flex joints between the engine and the side pipes.

https://www.amazon.com/Autarboor-Exhaust-Stainless-Double-Overall/dp/B09SYWZ83B/ref=asc_df_B09SYWZ83B/?tag=hyprod-20&linkCode=df0&hvadid=647188767054&hvpos=&hvnetw=g&hvrand=759760071169037642&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9018934&hvtargid=pla-1950467095831&mcid=3bfa209f7e8f311c97d5a85d9770b033&th=1

Not aesthetically pleasing, your packaging dilemma might require exhaust manifolds to provide room for the flex joint.
I agree repetitive repair is annoying. Back in 1983 I bought a new Saab 900 and when the exhaust rusted out at 50K miles I installed the factory recommended stainless system. The exhaust never rusted to 270K miles but the exhaust pipe just aft of the engine cracked about every 25K miles. Remove, weld, repeat.
jim

[TallerMike]

Mike, You should consider the contribution of metal fatigue to your problem. That is not just stress but a vibration at some frequency(s) that cracks the metal over time.
It is possible that with your engine mounts and your RPM operating range you have a sympathetic frequency/amplitude that your exhaust does not tolerate.
An engine mount change could help or flex joints between the engine and the side pipes.

Agreed - I'm suspecting it's some combination of vibration and twisting / torque which create fatigue on these welds and causes them to crack. I have the poly motor mounts from the kit, what would I replace them with?



https://www.amazon.com/Autarboor-Exhaust-Stainless-Double-Overall/dp/B09SYWZ83B/ref=asc_df_B09SYWZ83B/?tag=hyprod-20&linkCode=df0&hvadid=647188767054&hvpos=&hvnetw=g&hvrand=759760071169037642&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9018934&hvtargid=pla-1950467095831&mcid=3bfa209f7e8f311c97d5a85d9770b033&th=1

Not aesthetically pleasing, your packaging dilemma might require exhaust manifolds to provide room for the flex joint.


I feel like I've looked at this dozens of times now and stopped short of doing it. I really don't care about the aesthetics of it - it's hidden inside the car, and there's plenty of other random bits of metal in there with function over form. After reading about people using these on other cars, I'm worried that the flex might either amplify the vibration and/or also crack due to repeat fatigue. They're great for taking rotational torque from the engine, but not a good solution for fatigue without developing leaks. I'd probably try to replace with long tubes over this in hopes to be done with it.



I agree repetitive repair is annoying. Back in 1983 I bought a new Saab 900 and when the exhaust rusted out at 50K miles I installed the factory recommended stainless system. The exhaust never rusted to 270K miles but the exhaust pipe just aft of the engine cracked about every 25K miles. Remove, weld, repeat.
jim

Remove, weld, repeat - that's where I'm at!

[J R Jones]

Mike,
I am not a roadster guy so I am working with experience in development engineering including Harley Davidson vibration.
You have the source of displacement and vibration, a relatively long lever arm, and a relatively static side pipe.
The amplitude of the displacement increases with the length of the lever arm.
If you introduce a flex joint, it will adsorb some of the amplitude. Upstream the force remains, downstream it is reduced.
This technology is routine with OEMs and quality aftermarket exhaust systems, under car, where the (RWD) force is twisting and less amplitude. FWD engines bend the flex joint.
You have bending stress and higher amplitude, making your resolution an experiment.

FFR engine mounts may be dimensionally unique meaning that OEM replacements may change the engine position.
jim