The 5.7s Plastic Intake Manifold Bolts Loosen Over Time

Discussion in 'Challenger R/T Engine & Performance Modifications' started by RyansRT, Aug 8, 2022.

  1. RyansRT

    RyansRT Active Member

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    This is a common problem that not only happens to the 5.7 but also the 6.4, the intake manifold bolts pre 2015 should be 105inch/lbs, that is INCH/POUNDS not Foot Pounds, 2015 to present is 108inch/lbs.

    Check and tighten when the engine is cold, if your 5.7 is just not performing like it was check this. The tightening sequence for the 5.7 is below.


    5.7 Manifold.jpg

    Tightening Sequence for the 6.4 below.

    6.4 Manifold.jpg


    As you can see the tightening sequence is the same for the 5.7 and the 6.4. Ry
     
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  2. RyansRT

    RyansRT Active Member

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    When I had discovered mine were loose I would guesstimate they maybe had 20in.lbs. of pressure. Any looser than they were and they probably could have been turned using finger pressure. Once I discovered what the actual torque value was for mine 105in.lbs., I went to Harbor Freight and bought an Inch LB. torque wrench, cost 20 bucks. Since mine were so loose I tightened in stages something like 60, 80, 100, and then finally to 108, using the tightening sequence each time.

    Once back to the proper torque the engine cranked and ran smoother, but the first time I took it out and accelerated I was amazed at how much power returned. I guarantee if yours is seeming to have lost power and you find these bolts loose and tighten them back to spec, you will see a performance improvement.

    Do not gorilla these bolts use the proper torque wrench.
     
  3. fritzthecat

    fritzthecat Full Access Member

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    If they were that loose was the OBD throwing vacuum leak codes?
     
  4. Moparisto

    Moparisto Full Access Member

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    I like the new, aluminum, aftermarket manifolds. I'd like to see someone put an extension piece in the middle and jack up the length of the long runners another 3" in height/6" overall length or so. The low-end would be awesome!
    Since they have a series of flapper valves that switch to short runners at higher RPM, the change would not harm the high-RPM power.
    Dodge did a great job, I think.
     
  5. SRT-Tom

    SRT-Tom Well-Known Member Staff Member Super Moderator Article Writer

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    I am glad that my 6.1 Hemi came with an aluminum intake manifold.

    Challenger 005.JPG
     
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  6. Moparisto

    Moparisto Full Access Member

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    I used to not like those manifolds UNTIL I discovered that Ma Mopar made them have the fantasy/dream of airflow engineers the world over: the ability to have the computer automatically flip the internals of the manifold so they would go from the low-RPM long runners to the high-RPM short runners at some predetermined point.

    I am surprised someone in the aftermarket has not really gone to town to exaggerate the manifold's capabilities covering high and low RPM even more. Hmmm. maybe there's room for a new, 2000's version of the High Rise Manifold needed. Who wouldn't want to have an excuse for a functional Power Bulge in their hood?

    Can you imagine how much racers in the 1960's would have loved to get their hands on such technology?

    The closest thing I saw to it in the 1990's was the ZR1 with four-valve heads that blocked off one of the intake valves' runners at low RPM for better flow velocity, then allowed both at higher RPM.

    BTW, one of the winners (I think) of the Engine Masters Challenge one year had a four-valve Ford V8 where he had individual runners on each exhaust valve leading to a Tri-Y header, too. Two sets of four-into-two-into-one then into one collector on each side. It was interesting to see.

    Anyway, back to the ZR1: Yes, each valve had its own intake runner all the way to the plenum. The engine in those cars was exceedingly expensive, according to some spokesperson for GM. It gave rise to the birth of the LS series of motors for Chevrolet, and those have been very successful engines, both inexpensive and with lots of performance potential.
     
    Last edited: Aug 9, 2022
  7. RyansRT

    RyansRT Active Member

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    Yes it was.
     
  8. RyansRT

    RyansRT Active Member

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    The only problem with those is they get hot which is partly why Dodge stopped with the aluminum 6.1 manifold and went with the plastic on the 6.4.
     
  9. RyansRT

    RyansRT Active Member

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    That has always looked fantastic on the engine, and your bolts stay tight, but you do have the added heat soak of the aluminum intake, but that is a small price to pay for it's performance.

    Your under hood looks fantastic, the manifold is so clean! :)
     
  10. RyansRT

    RyansRT Active Member

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    Only the plastic 6.4L intake manifold has the runner switching capabilities.