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Discussion Starter #1 (Edited)
To make a long story short and just get down to the details I discovered my 5.7s intake manifold bolts were loose, very loose, estimated around maybe 20 in.lbs. maybe even looser, this was contributing to a loss of power.

Seeing as how my Challenger is a 2015 with 50,500+ miles on it, things loosening over time is going to happen. So I started researching online to discover what is the actual torque value of these 8mm intake manifold bolts, the online information was all over the place.

When it comes to something like this you want your information from the horses mouth so to speak, so from the 2015 Shop Service Repair Manual. Using the sequence shown in the illustration below, tighten the Intake Manifold Bolts to 12 N.m or 9 ft. lbs. or 108 in. lbs..


Manifold Tightening Sequence.jpg


Note: The illustration above is a 6.4L intake manifold, however the tightening sequence is the same for the 5.7L.

If you have some time year wise, on your Challenger you need to check the torque of these intake manifold bolts with engine heat and cold cycling they will loosen up over time. Mine was so loose I have no idea how loose they actually were, in the beginning because I tested their tightness with a 3" ratchet handle wrench, which only allows wrist pressure.

I knew I needed to torque them but I was concerned going straight to 108 in. lbs., and though you can tighten a few turns at a time following the sequence, until you reach the torque limit.

I started at 30 in. lbs. and heat cycled the engine, meaning I drove it and then parked it overnight and allowed it to completely cool down, and then the next morning tightened another 10 in. lbs.. Which took me 8 days to reach 108 in. lbs..

Do you have to do it like I did, Heck No, Absolutely Not!

For me I just wanted it tightening evenly across the entire intake manifold, and heat cycling at the same time, now I am retired and I have the time to do it that way, you may not.

If you have some age on your car check the intake manifold bolts, you could be loosing power, or even worse if it gets too loose you could suck something in there you don't want.

Caution: Torque when the engine is cold, and absolutely use a known accurate torque wrench, do not do this with a regular ratchet trying to estimate the tightness, if you break off one of these bolts, you are screwed.

Ry
 

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Thanks for sharing this amigo. I'll be checking mine tomorrow as my challenger is a 2016 with just a little over 66,000 miles.
 

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Discussion Starter #3 (Edited)
Thanks for sharing this amigo. I'll be checking mine tomorrow as my challenger is a 2016 with just a little over 66,000 miles.
Yours are probably loose, post back what you discover, Please.

Interesting yours is a year newer than mine but with 15,500 more miles so they should be probably as loose as mine were.
 

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Discussion Starter #4
For the record I think heat cycling has a direct effect on the intake manifold gaskets seating, because yesterday morning I reached the 108 in. lbs. value and drove the car yesterday.

This AM before I cranked it up, I decided to check the 108 in. lbs., and every bolt had to be snugged at least a 1/4 turn to get back to 108 in. lbs..

Note: I had no idea that this was the reason that Sean was having a problem getting my Hemifever tune dialed in, he had thought it may be my use of gasoline that had Ethanol added, and suggested I use non ethanol gasoline, but all this time the problem was the intake manifold bolts were loose.

The engine response has changed drastically, I've actually gained power, and it did not cost me a penny! :) Ry
 

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Is this a problem for those running 6.1 intakes I wonder? Or is the issue just contained to the plastic intake manifolds?
 

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Discussion Starter #6
Is this a problem for those running 6.1 intakes I wonder? Or is the issue just contained to the plastic intake manifolds?
That's a good question, that I don't know the answer to.

The characteristics of the plastic vs the aluminum expansion and contraction, I would assume the plastic to be worse.

Maybe someone with those intakes will find this thread and chime in on it, with actual tested facts of course?
 

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I hit the ground running first thing this morning, but I’m planning to put a proper wrench on mine to get some torque numbers also. My car is a 2016 Shaker with 83,000 miles on the clock.
 

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Discussion Starter #9
I hit the ground running first thing this morning, but I’m planning to put a proper wrench on mine to get some torque numbers also. My car is a 2016 Shaker with 83,000 miles on the clock.
Thanks, I believe this is a common problem with the 5.7L intake manifold and the more we can learn about it the better for everyone, mine cannot be an isolated case.
 

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Right or wrong, I have a Harley Davidson, (should be read as “ I have Locktite and am not afraid to use it”)
I’ll probably throw a dab on those intake bolts just because I do not like self loosening fasteners. I can’t imagine that the gasket is crushing that much, so I’d bet it’s the bolts themselves. I’d also suspect there are metal bushings in the intake holes, which means the amount of force exerted on the sealing surfaces does not increase with additional bolt torque once bushing has contacted the bolt head on one end and the cylinder head on the other.
 

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Discussion Starter #12
Right or wrong, I have a Harley Davidson, (should be read as “ I have Locktite and am not afraid to use it”)
I’ll probably throw a dab on those intake bolts just because I do not like self loosening fasteners. I can’t imagine that the gasket is crushing that much, so I’d bet it’s the bolts themselves. I’d also suspect there are metal bushings in the intake holes, which means the amount of force exerted on the sealing surfaces does not increase with additional bolt torque once bushing has contacted the bolt head on one end and the cylinder head on the other.
Didn't you say yours were loose and you used a regular ratchet to tighten them some?
 

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Looking forward to learning what you discover?
I was hoping the car would be home by today but they are not done with it because of the huge amount of rainfall we've had over the last three weeks. It's rained almost every single day. The guy that's doing the tuning actually road tunes the car and he doesn't drive in the rain with customers vehicles. The injectors and bypass valve should be about done just waiting on good weather for tuning. Hopefully by next Friday the car will be home. I will check the intake manifold bolts at that time with a torque wrench.
 

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Didn't you say yours were loose and you used a regular ratchet to tighten them some?
That is an accurate statement. I just put a little on each fastener, but once I learned the proper torque spec, I’m certain they are nowhere near what they are supposed to be. At most, we can ascertain that they were also loose, but not so much as to just how loose they were before.
 

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That is an accurate statement. I just put a little on each fastener, but once I learned the proper torque spec, I’m certain they are nowhere near what they are supposed to be. At most, we can ascertain that they were also loose, but not so much as to just how loose they were before.
I checked them today. What I found was they were on average half the torque value they should have been. None were super loose, but none were actually tight, either. I did discover a little damage on one of my fuel injector wires from some little fur covered varmint. Made repairs and reinsulated the wires before putting the shaker base plate and scoop back on.
 

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I did mine last weekend. They were loose, not sure exactly how loose. I started with 70 in/lbs, then 90 in/lbs and finished with 105. Made a real difference.

Forgot to add mine is a 2014 with 28,000 miles.
Is that set with a cold or hot engine?
 

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Good question. I had to move it into the garage. It didn't run more than 30 seconds. I let it sit about 30 minutes. So it wasn't overnight stone cold but it never got close to operating temperature.
 

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Yours are probably loose, post back what you discover, Please.

Interesting yours is a year newer than mine but with 15,500 more miles so they should be probably as loose as mine were.
I haven't been able to do this yet. I'll be checking them tomorrow afternoon at my buddy's shop before we put it on the lift. I'll let you know what I discover. I am picking up the oil cc today and will he installing that as well.
 
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