Does the powertrain warranty cover the manifold bolts?

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Ken226

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You know thats really not much thermal growth. .006-.010. A piece of paper is .004.

Your right, its not much at first thought, buts its a helluva lot of extra stress when the bolt is stretched that much.

Ok, ill go ahead and work out the math on it. I get the impression that most are just gonna look at the numbers and guess "aw shucks, that aint aint nothin".

Be back in a few minutes.
 

Ken226

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You know thats really not much thermal growth. .006-.010. A piece of paper is .004.

Ok, i worked it out on the side of my coffee cup (i i couldn't find a peice of paper).

IMG-20191221-140702724-MP.png

.00678" additional stretch adds 5416.2 psi of tensile stress to the screw, thats already at 65,301 psi.

I didnt calculate for .0108", but it should be just about 10,000 additional psi of stress.

Over and over, every heat cycle.

Every part has a lifespan, and a part that is constantly stretched and relaxed will fail at a certain number of cycles. The goal should be (and probably was) that the failure occurs at a point beyond the expected life of the vehicle.

The problem is, many of them are failing well within the lifespan of the vehicle, and some more than once.

If a guy stretches his manifold screws to....
84% of its breaking point:

75,301 (towing up mountains in winter) divided by 90,000 (max tensile to yeild) = .8366

A couple times a week for years, how long till they snap?
 
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Pull Ya

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Did someone say "engineer"??????? I bet you got a professor somewhere looking at that coffee cup, just shaking his head---- LOL
Jay
 

18ram18

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As long as that bolt does not exceed its proof load it will stretch and relax that .010. BUT since we all know these bolts eventually snap, we can only assume that FCA engineers have failed bolting fundamentals 101.
 

tomb

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oil changes are important-i only put 4000kms /yr but still use
I meticulously maintain my ride and had it happen to me....
maybe i am lucky -but 2012 has had no issues with either dont want to jinx myself so i am sifning o
I have had 3 or 4 , not counting the old hemi, never had a bolt break, or a cam , lifter go out.
I sometimes wonder if it could be people with lift kits and bouncing around in the hills? Don't know
I was wondering the same thing-mine is a 2012 Bighorn and never had an issue under the hood at all. I use pup oil and change every 5,000kilometers only because that is a year for me. Maybe lucky and I hope I didnt just jinx myself!

DSC00560.JPG
 

OCDTech

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Your right, its not much at first thought, buts its a helluva lot of extra stress when the bolt is stretched that much.

Ok, ill go ahead and work out the math on it. I get the impression that most are just gonna look at the numbers and guess "aw shucks, that aint aint nothin".

Be back in a few minutes.


What about if they/someone used washers under the bolt heads, brass? some certain alloy with just the right malleable qualities to absorb the super slight expansion. Or would this cause a never ending loosening issue?
 

McBroom

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What about if they/someone used washers under the bolt heads, brass? some certain alloy with just the right malleable qualities to absorb the super slight expansion. Or would this cause a never ending loosening issue?
Great question

Blue Mule
 

Ken226

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What about if they/someone used washers under the bolt heads, brass? some certain alloy with just the right malleable qualities to absorb the super slight expansion. Or would this cause a never ending loosening issue?

Brass washers wouldn't likely help.

Brass anneals when heated then cooled. It becomes really soft. Any rifle cartridge reloader will be familiar with the properties of brass, and have annealed rifle case to soften the necks.

The annealed brass would likely squish thinner as the manifolds expand, but would not un-squish when the manifold cooled.

If the washer material was hard enough not too squish, it likely wouldn't accomplish anything.

The springs could work, if they were strong enough to exert thousands of lbs of force, and could withstand the heat.

The correct fix would be thinner manifold flanges and/or shorter, larger diameter screws.

Compare the flanges of a Chevy ls1 manifold to the flange thickness of a hemi manifold.

LS1
download.jpg

Hemi
61x-OQi2q-Hy-L-SX425.jpgbest kind of betta fish
 
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OCDTech

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Brass washers wouldn't likely help.

Brass anneals when heated then cooled. It becomes really soft. Any rifle cartridge reloader will be familiar with the properties of brass, and have annealed rifle case to soften the necks.

The annealed brass would likely squish thinner as the manifolds expand, but would not un-squish when the manifold cooled.

If the washer material was hard enough not too squish, it likely wouldn't accomplish anything.

The springs could work, if they were strong enough to exert thousands of lbs of force, and could withstand the heat.

The correct fix would be thinner manifold flanges and/or shorter, larger diameter screws.

Compare the flanges of a Chevy ls1 manifold to the flange thickness of a hemi manifold.

LS1
download.jpg

Hemi
61x-OQi2q-Hy-L-SX425.jpgbest kind of betta fish



I see the LS1s there look like separate at the flange. I had a 91 5.0 with aftermarket headers, they were separate. When i seen those i though that was the perfect solution for exhaust leaks, seal individually right. Well until i went to change the gasket. The car sat for a week, for thermal reasons, i undid the bolts and in the time it took to get my stuff together, hour or two maybe, could have been a day not sure. Anyway the individual tubes had moved just so slightly, This was one pain in the **** to get all those bolts in. I had to get a few then get a floor jack under them jack up a little to finally line up the others.

Thanks for the insight though.
 

Ken226

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I've thought about pulling my manifolds and milling the flanges to about half the current thickness, but if I go that far, I should probably just put headers on.

Headers have a thin, strong flange that would cure broken screw issue. I just need to find some that won't rust away in the pacific northwest humidity.
 

McBroom

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I've thought about pulling my manifolds and milling the flanges to about half the current thickness, but if I go that far, I should probably just put headers on.

Headers have a thin, strong flange that would cure broken screw issue. I just need to find some that won't rust away in the pacific northwest humidity.
ARH are the best headers for a hemi.

Blue Mule
 

Ribtipram

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The 454 before the vortec(96 i think) had similar probs with the intake and exhaust man's heat expansion. They changed the tubes to be separate so they could move Individuality from one another. I work in a shop where we heat steel cases to drop carbide in and believe me .006 is a lot of extra stress.
 
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