Question on Exhaust Manifold Replacement - bolts

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MarineBSP

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My 2018 Laramie CC with 5.7L Hemi suffered the most common broken rear-most exhaust manifold bolt on the passenger side (PS) ten months ago. But with < 60K miles, my dealer replaced the manifold and hardware under warranty. Only the bad side was replaced, and since it was a warranty job, I could not keep the old manifold.

I figured I’m on borrowed time for the driver’s side (DS), so I purchased recycled OE exhaust manifolds, both DS and PS, hoping these will be well heat-cycled. A local machine shop flattened them for me, and the mating surfaces are very good. I plan on swapping out both sides (hopefully without broken bolts on driver’s side). I’ll crack the bolts loose working back from the front to have the least stress on those back bolts when I loosen them. I have new gaskets & hardware.

My question for the forum of wisdom, knowledge, & experience (yeah, opinions too):

There are some bolt length differences in OE bolts. A running change added 5mm to the bolt lengths after my truck was built (from 06/2018 on). Is that just to accommodate the tie bars they added back then? The bolts went from 50mm long to 55mm long. I have 55mm ARP bolts and Mopar bolt-studs, but I’m concerned in case the holes in the head are not deep enough or threaded deep enough. I will probably be OCD and run bolts in without the manifold and gasket to check this. If I were the design guy, the threaded holes would have a safety margin . . . But after resurfacing, the middle of my “new” manifolds will not have as thick a shoulder. If needed I’ll add lock washers (okay idea or not ?). This is the difference between doing this job once-in-a-lifetime versus three times a week as a part of a shop’s regular work load.

I won't get to the job for a week or so because of Fall cleanup, but I'l post when done.

Thanks for input.
 

Jeepwalker

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I don't have an answer for you on your specific bolt length.

You're wise to be concerned about bolt depth. Whenever I get to a job like this where machining was involved, I typically install a couple bolts just snug (with plenty of washers on them), to hold the manifold on ..plus gaskets, etc, then insert a wire or depth gauge, to verify the length of the threads (not just the hole depth). Then hand thread in the new manifold bolt (not tight) to verify length, remove a safety factor, then washer up, or trim bolts accordingly.

I would probably go to the hardware store and get hardened lock washers if you need them. I wouldn't stack lock washers. Then get either a thicker washer, or better yet, trim the bolt length with an air cut-off tool or whatever you have (and clean up the thread tip).
 
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grizzstang

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I don't see any issues with using lock washers but I would probably use a standard stainless steel washer or trim the bolts if I needed to.
 

Gero

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A bit off topic but related, I heard many people suggest ramflex gaskets. I hear it will help prevent broken studs in the future.
 
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MarineBSP

MarineBSP

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Well, here's what I did – not a guarantee, hope it's not too redundant, use at your own risk, posted because I wish I had more details in one place, etc.

Summary of background I found on exhaust manifold replacement:
  • Driver’s Side (DS) is harder than Passenger Side (PS) Side because of dipstick, steering column, AC, and Evap lines.
  • I heard Mopar suggests jacking up the engine for more clearance ? But I’ve never seen a video showing this.
  • Shop manual says remove dipstick from block, but there are disaster tales. One YouTuber cut it and re-joined w. fuel line. Others bend it - me too.
  • Removing the Y-Pipe simplifies manifold removal & install, but the Y‑pipe is heavy, another job, and easier on a lift with 2nd person.
  • New manifolds seem to warp and break bolts like the originals, so flattening old, heat-seasoned manifolds and installing with new hardware and quality gaskets seemed my best long-term solution.
  • There appears to be a 2018/19 manifold redesign: Stiffener stays, threaded holes in manifold to attach to Y‑pipe, and stainless steel ‘corner’ studs. Are manifolds still an issue for 2019+ trucks ?
I planned to replace my spark plugs at the same time, because I read that changing from below was easier than from above.

As described, I used FelPro gaskets and ARP bolts (55mm) with washers (four per side, only sold in 5-packs, Summit Racing). The inserted depth of the ARP bolts matched my old bolts when the washers were used. I ordered RAM studs for the four corner positions. I received the new design, stainless studs, even though the part number I used was for the old-style studs. These stainless studs are about 5mm longer under the head to use with the stiffening stays they added on later trucks. I added stainless steel washers (thanks, Grizzstang) to make up for the length difference on these studs and on the bolts as needed. I checked and adjusted so that the same length of stud (or bolt) would go into the head as when it was original.

The job was done with rear wheels chocked, the front jacked up resting on 6-ton jack stands, and front wheels removed. For plug replacement, the intake tube from air filter to throttle body and the engine cover were removed. Then the DS wheel well liner (8mm head screws and 3 plastic push retainers) was removed.

Y-pipe bolts and their square nuts were next (the clips were rusted and broke, but nuts and bolts were reusable). The four 10mm nuts holding on the heat shield were removed, then I pulled the dipstick and coaxed the dipstick tube around an AC line and bent it down closer to the steering column. The heat shield was wrestled out the back and bottom to reveal the studs and bolts – all still intact. Starting at the front, I cracked loose the double studs (13mm heads) that mount the heat shield and loosened more than 2 full turns. Then I loosened the bolts (10mm heads) in the center portion of the manifold two turns each, starting in front and moving back. My logic was to remove as much stress as possible on the rear studs that often break first, hoping to improve odds of getting them out in one piece.

Using a wide variety of 10mm and 13mm sockets, extensions, and universal joints, all the fasteners (4 studs, 4 bolts) came out intact. Getting them all out complete was great, but the next puzzle was getting the old manifold and gasket out and putting the new parts in. My goal was to avoid any damage to the new gasket while fitting it and the refurbished manifold into place. I taped cardboard over the sealing / port area of the gasket to protect it once in place. The new gasket was fiddled in from the rear, but above the frame rail (the heat shield on the frame rail can be bent out of the way). I ‘hung’ the gasket with a bolt in the position that fits into the slot on the manifold lower flange. With some considerable trial and error, I inserted the manifold up from the bottom rear (the cardboard gasket ‘protector’ helped). It took a while to get all the studs and bolts in and torqued to spec. The steering column, AC lines, dipstick tube, and Evap line to the gas tank all seem to be exactly where a person wants to put a tool, a hand, or the parts – this would be easier on a lift. I separated the Evap line at the connector for better access. I torqued all eight fasteners to 10 ft-lb with a 1/4-inch drive torque wrench, and then went to 18 ft-lb with my large torque wrench. For two fasteners I could not reach with my large torque wrench, I turned the bolt or stud the same extra angle that the other six fasteners took between the two torques. Then the heat shield went back on. The manifold I removed had about 40-50 thousandths (1mm) warp measured end-to-end, so replacement was not wasted.

I spread this out over an afternoon and a following morning. My total elapsed work time was 5 to 6 hours – not only the DS manifold, but includes jacking, liner removal, and over an hour cleaning and refitting the wheel well liner to my liking after I finished the manifold and the spark plugs. I tend to be OCD about anything I haven’t done before. I postponed the PS manifold ‘re‑replacement’ for now. I have the PS part and hardware, it’s good for now, and I just have to do it before it goes bad and breaks a bolt again.

Spark Plugs: As previously planned, I replaced spark plugs too. I set no speed records, BUT I’m really happy I did the DS plugs while the wheels were off and the liner was out. Working under the brake booster to remove and replace coil packs and plugs was hard enough, and I think it would have been worse from above. The PS side plugs were almost simple after the DS. When replacing the PS coil packs and plugs, it was helpful to release the snap clip locating heater hoses and move them out of the way as well as releasing zip ties on the main wiring harness to let it flex to one side or the other. The plugs still looked amazingly good. I was concerned whether the plugs might be seized if I waited another 2 to 3 years for the 100K mile ‘recommendation’.

Feels good to have this job done. Thanks to all who addressed my questions and for the previous posts / advice on manifold and spark plug replacement!


PS - The Gearwrench magnetic swivel spark plug wrench, recommended by many board members, is way worth it. I can hardly imagine doing plugs without it
 

EdGs

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Sounds like you did a good job getting it fixed.

On my '15, I used Everbuilt hardware from Amazon. No issues at all. I have a 2wd, so pulling the dipstick tube was easy, 4wd is harder, so I'm told.

One member here went 220k miles on the oe plugs, and they still looked excellent, so 100k is a cakewalk. That Gearwrench tool is the sh*znit, for sure.
 
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