5.7 hemi exhaust manifold options

[desertrunner]

For anyone out there running a 5.7 hemi in their JK curious what options are out there for manifolds? Mine has fallen victim to the manifold bolts breaking and I'm trying to figure out the best way forward. Most of the Ram guys out there have been down the road of replacing the bolts 2 to 3 times in less than 100k before ditching the stock manifolds and doing something like a shorty header or custom exhaust. Seems like some doing the swaps on wranglers are able to make 6.1L and 6.4L manifolds fit but have to trim motor mounts or upper control arm brackets, or even frame notch (non of which id like to do). Id love for this not to be a reoccurring issue by just replacing the bolts and hope it doesn't happen again but its a tight fit and I'm skeptical about trying some different without knowing it will fit.

 

[Snboarder113]

What’s the actual fail point? Just the bolts? Are there upgraded bolts / studs you can use instead? Is it just the weight of the headers and exhaust is too much? Sounds like a trip to the hardware store would fix it permanently, just don’t overtorque.

 

[desertrunner]

What’s the actual fail point? Just the bolts? Are there upgraded bolts / studs you can use instead? Is it just the weight of the headers and exhaust is too much? Sounds like a trip to the hardware store would fix it permanently, just don’t overtorque.

from everything i have read cyl 7 and 8 tend to run hotter and that's the stud that hold on the heat shield in the back and those are usually the first to go. Both drivers and passenger rear bolts on mine are broken. If left longer some people have had 2-4 bolts broken flush to the block but i wont know how many are broken until i pull the manifolds. I guess something about the aluminum head, cast manifolds, and steel bolts lends itself to uneven heating and cooling causing the bolts to fail. Most likely i am going to try aftermarket bolts with some new gaskets but on the ram forums it seem hit or miss on it happening again.

 

[Ddays]

Has anyone tried using studs made out of one of the super alloys like inconel?

 

[desertrunner]

Has anyone tried using studs made out of one of the super alloys like inconel?

Not that I have come across

 

[Snboarder113]

I guess I just don’t see how something like a grade 8 bolt wouldn’t fix the entire issue.

 

[Bierpower]

The newer gm manifolds are cut through each bolt hole on the bolting flange. I wonder if that's to offer enough relief for the manifolds and heads to expand at different rates. I'll snap a picture when I get home.

I know the older 6.0 Chevys had exhaust manifold bolt problems but it was closer to 100-150k miles.

I would think the grade 8 would solve the issue but likely metric so grade 10.9 or 12.9

 

[kevman65]

I'm going to hazard a WAG.

You have three dissimilar metals in direct contact to each other. Aluminum heats up faster, but gives up it's heat easier. Cast iron takes the longest of the three to heat up, and holds it's heat forever. Then you have the mechanical connection, the studs or bolts. The bolts being steel and of unknown temper or strength, are less mass than the other two parts. They will heat up quickly because of location. One part will cool sooner than the other part, again because of location.
These bolts are losing their temper, becoming brittle at the mating surface between aluminum and cast iron.
You can try heat treated studs or bolts, I would have no idea of what hardness you would need to look for as I don't know the heat range of the exhaust manifold, the amount of force being applied by the bolt up and so on.

This is something you may want to approach a manufacturer (ARB is the only one coming to mind) about. They specialize in automotive fasteners and probably have an idea of what is needed.

If your aftermarket manifold choices are steel, that is going to help with heat dispensation. Thinner material, less mass, give up heat evenly and faster than cast iron.

 

[Snboarder113]

I'm going to hazard a WAG.

You have three dissimilar metals in direct contact to each other. Aluminum heats up faster, but gives up it's heat easier. Cast iron takes the longest of the three to heat up, and holds it's heat forever. Then you have the mechanical connection, the studs or bolts. The bolts being steel and of unknown temper or strength, are less mass than the other two parts. They will heat up quickly because of location. One part will cool sooner than the other part, again because of location.
These bolts are losing their temper, becoming brittle at the mating surface between aluminum and cast iron.
You can try heat treated studs or bolts, I would have no idea of what hardness you would need to look for as I don't know the heat range of the exhaust manifold, the amount of force being applied by the bolt up and so on.

This is something you may want to approach a manufacturer (ARB is the only one coming to mind) about. They specialize in automotive fasteners and probably have an idea of what is needed.

If your aftermarket manifold choices are steel, that is going to help with heat dispensation. Thinner material, less mass, give up heat evenly and faster than cast iron.

I think you meant ARP, I agree with your assessment of different metals and heat cycles. But I’m pretty sure that’s not special to a hemi. Everyone uses aluminum heads now and cast manifolds, I think they must just be shitty bolts.

 

[kevman65]

I think you meant ARP, I agree with your assessment of different metals and heat cycles. But I’m pretty sure that’s not special to a hemi. Everyone uses aluminum heads now and cast manifolds, I think they must just be shitty bolts.

That's why I mentioned specialty fasteners and heat treatment.
Manufacturers are going to use the cheapest material that will get them out of warranty time.

And yes, I did mean ARP. I know they do in house heat treatment. Different areas of the engine get different hardness values.
I'm used to using the Rockwell Hardness Test for piping and pressure vessels, don't know if they use that test or a different one for automotive.
But they could probably tell you which bolts/studs to use in the application.

 

[desertrunner]

On the AEV forum there was 1 mention of the ARP bolts but I go so lost on my initial search of there sight. I clearly need to know a bit more info on the size and pitch before seeing if they have bolts that will work.
I agree with the general thinking that if the bolts are weak, buy better bolts, problem solved. Just gotta find the right ones.

 

[Snboarder113]

On the AEV forum there was 1 mention of the ARP bolts but I go so lost on my initial search of there sight. I clearly need to know a bit more info on the size and pitch before seeing if they have bolts that will work.
I agree with the general thinking that if the bolts are weak, buy better bolts, problem solved. Just gotta find the right ones.

Just dont over torque. Better bolts WILL rip aluminum threads out if you don’t use a torque wrench. ARP makes great strong stuff (like head bolts on 1000hp drag cars) so if they offer a replacement set I’m sure it’s worth it.

Edit
Googled 5.7 hemi exhaust bolt upgrade. I’m sure you’ll wanna go more in depth to make sure the ones you get fit exact year manifolds (or use this as an excuse to upgrade to racing headers )but they exist.
first result
ARP 440-1101 Header Bolt Kit (6ptMopar 5.7/6.1L Hemi) https://www.amazon.com/dp/B01KHLIS5...abc_PWKC2352P863TSXV2DAX?_encoding=UTF8&psc=1

 

[Brute]

I had two broken exhaust manifold bolts on the 5.7 in Brute as well...happened at about 60k miles...I had them replaced with oem bolts...this was about a year ago.

good luck with finding a resolution...

 

[kevman65]

On the AEV forum there was 1 mention of the ARP bolts but I go so lost on my initial search of there sight. I clearly need to know a bit more info on the size and pitch before seeing if they have bolts that will work.
I agree with the general thinking that if the bolts are weak, buy better bolts, problem solved. Just gotta find the right ones.

Contact ARP direct. Tell them WHY you need new exhaust manifold bolts. Probably won't be the first time they've heard the problem.
They'll probably point you right to the bolt pack you need.
Then shop the part number for best price we're all cheap bastages

 

[desertrunner]

Just dont over torque. Better bolts WILL rip aluminum threads out if you don’t use a torque wrench. ARP makes great strong stuff (like head bolts on 1000hp drag cars) so if they offer a replacement set I’m sure it’s worth it.

Edit
Googled 5.7 hemi exhaust bolt upgrade. I’m sure you’ll wanna go more in depth to make sure the ones you get fit exact year manifolds (or use this as an excuse to upgrade to racing headers )but they exist.
first result
ARP 440-1101 Header Bolt Kit (6ptMopar 5.7/6.1L Hemi) https://www.amazon.com/dp/B01KHLIS5...abc_PWKC2352P863TSXV2DAX?_encoding=UTF8&psc=1

yeah everything I'm seeing on their site is for aftermarket headers and not the stock manifolds but i emailed them to see what they got. Something like a shorty header would be great but clearance is so tight i really doubt they would fit without other modification.

 

[desertrunner]

Contact ARP direct. Tell them WHY you need new exhaust manifold bolts. Probably won't be the first time they've heard the problem.
They'll probably point you right to the bolt pack you need.
Then shop the part number for best price we're all cheap bastages

I like the way you think haha

 

[desertrunner]

I had two broken exhaust manifold bolts on the 5.7 in Brute as well...happened at about 60k miles...I had them replaced with oem bolts...this was about a year ago.

good luck with finding a resolution...

good to know thanks! a higher quality bolt seems to make sense but maybe they changed something with the OEMs and they will hold up just fine. I cant imagine why a jeep that lived in Hawaii for 5 years then ended up in a North Dakota winter would have some funny problem arise id be pissed too lol

 

[Bierpower]

Here's the GM manifold.

Looks like the split all of the inner holes and the two outers are elongated to allow room to expand and contract.

It may be worth taking a carbide burr bit and clearancing those end holes a little to see if it helps.

 

[desertrunner]

Ended up going the OEM route. Talked to the parts counter guys here and they have a kit ready to go since its so common (which is sad). But they did say it's all superseded part numbers and they have very few repeats back in for the same issue. Guess time will tell. I got the passenger side tore down tonight and everything came out relatively easy just 1 broken stud that was easy to pull. The drivers side is a bit more difficult with clearance and has been ticking a lot longer so fingers crossed that goes as smooth.

 

[desertrunner]

Passenger side is back on and torqued minus the heat shield. When I fired it up it sounds clean with no leaks so hope that's good to go.
The drivers side is being a real bitch for clearance trying to get it out. Got 1 bolt that has been fighting me trying to get any leverage on. So far though only 1 broken stud and it's at the back with easy access, however it appears to be broken at the block so that will be fun to get out. I'll know more once I can get the manifold off though.