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post #1 of 7 Old 10-16-2021, 12:41 PM Thread Starter
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It seems that I have an exhaust tick coming from the exhaust manifold on the driver side. I know the 4.7s have a habit of cracked exhaust manifolds so I prefer to upgrade to a nice aftermarket set and just do my entire exhaust at the same time. I saw that Doug Thorley makes or made them but are out of stock. Not sure who else makes them or if Dougs will make them again. Thank you

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post #2 of 7 Old 10-16-2021, 05:04 PM
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No one else makes them. From what I understand they are a royal PITA putting in. Martinbuilt on YT has a set on his, check out his install video.

2004 Limited, 4.7 modded slightly, IRO 3" RockLink LA front, adjustable SA rear, Bilsteins, Addco bar, JKS disconnects. Coming attractions include 242hd, IRO SYE and Woods DS right after the new engine/trans..
1974 Ironhead Sportster, total custom
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post #3 of 7 Old 10-16-2021, 05:47 PM Thread Starter
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Thank you for the input. Hopefully they come back in stock at dougs. I will definitely check out the video.
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post #4 of 7 Old 10-17-2021, 03:56 AM
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Good luck. Those broken bolts should be fun to remove. I prefer my 4.0. There’s enough room to work on it. It’s probably worse than the 09 f150 I did at work a while ago since it’s in in a smaller vehicle with no wheel well access. Pull the engine
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post #5 of 7 Old 10-18-2021, 12:22 PM
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The manifold is not likely to have cracked unless there was an "event" that put stress onto it from downstream like a high-center get stuck or way-serious rear end collision. Even then the exhaust is designed to bend away from pushing up to the manifold.
More often one or 2 bolts have snapped due to a poor spec from the factory. Removing the downpipe is not fun but the snapped bolts typically come out easily and there is usually enough to grab onto to twist out. The revised bolts and gasket from Jeep are not cheap but they last. They have a larger shank and shoulder design. The gasket is a little different too but I forget in what way exactly.
I did the driver side on my 2000 4.7 and the passenger side was fine. It snapped at about 160K miles and 6 years later at 235K miles it was still fine, even after a hard rear-end collision that totaled it.

On both of my 04 4.7HO units, these bolts have not snapped yet but occasionally, I'll spray the downpipe bolts with some penetrant, knowing that day may come.

"We have it totally under control. Its one person coming in from China. We have it under control. Its going to be just fine." ~D. Trump, Jan 22, 2020.
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post #6 of 7 Old 10-19-2021, 07:48 AM
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I don't recall anyone on here reporting cracked exhaust manifolds on a 4.7. However, MANY of us have had to replace the bolts and studs on the drivers side. I think I paid about $28 for the complete set of bolts, studs, and nuts (for just the one side!) from a Mopar dealer on ebay a few years ago.

As for headers, they aren't magical for stock engines, but they are guaranteed to bake the life out of every plastic bit and wiring insulation under the hood. They raise underhood temps a lot.
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post #7 of 7 Old 10-19-2021, 07:55 AM
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I think someone on here mentioned that Thorley would do a run of the 4.7 headers if there's an order for ~5 or more sets?

Maybe try to get a group buy and see if there's enough interest?

The thing is, with the Thorley headers going for around $1000, that's a VERY big percentage of the cost of the whole vehicle so who knows how much interest there will be.

Personally, while I'm sure they would provide a performance benefit, I'm not sure the benefit would be enough to offset the cost and hassle of installing them.

Edit: Found it.

It was @Kolak who mentioned it. I tagged him so he may have some more input.

They're not discontinued but Thorley hasn't made a batch in awhile. They would if there was sufficient interest - they want me to buy at least 5 sets in order to start a batch.


2004 GC Overland 4.7 HO
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