The expansion differences between the two metals is absolutely tiny. A micro-meter is one MILLIONTH of a meter........ so, the movement distances from two dissimilar metals here are going to be microscopic. Not sufficient to cause gasket failure in and of themselves. If it were, aluminum heads on a cast iron block would not work...... after all, expansion of cast iron is even LESS than that of the steel plenum plate.

 

Again, I don't disagree with it..

It may have to do with simple types of gasket.. fwiw, I also lend more credit to length of bolts, but that doesn't make it proven..

It is proven the plate works through countless installs here.. when done right, its conversation over.. why risk going in there again if you can do it once and forget it the first time?

 

+1^10 powah

It would be in everyone's best interested to see the TSB or w/e verbage (original) from Chrysler regarding the improper length of bolts. This is not to disregard people passing the information on that do know and have seen it, more importantly to pass on Sourced/Documented technical information. Just like a I asked for it over here. The bolt length is a critical parameter to maintain the DESIGN preload of the joint. The torque is calculated to achieve that, among other things, like not exceeding bearing stress of the flanges.


I'm not fully discounting this effect, however, I agree it is in the noise from a separation of the joint aspect. However, I wouldn't be surprised if there was an aligning of the moon, stars, comets, etc. for a certain type driver that pushed their engine to create just a fast transient thermal load or LARGE delta T to cause a snip of separation.

As for the example on the heads, again, the bolts (those are TTY) are calculated to meet the preload for which to hole the maximium pressure load of the cylinder firing. Severe overheating with excessive cycles that go outside of that (NOS) --> makes short work etc. as an example.


Anyone actually paid attention to the torque values for replacing the original steel plate and then looked at for the Aluminum plate? Easy to soure Hughes. I presume same for APS. Ebay plates....no clue.

 

Besides the bolts being too long, if you look at the plate, some of the bolt holes are way too far apart. Using the thicker aluminum plate helps with this. The steel plate bends, kind of like a valve cover or oil and tranny pan. Put that steel plate on a flat surface after it's off and you'll see, that between the bolts is a major gap.

 

Thanks, I kept searching for "plenum plate".

 

My steel plate leaks no oil after the fix.

 

As I've read through many really great posts from HeyYou,ZMAN, Augiedoggy, & Wh1t3Nuckle regarding the plenum stuff,I am amazed at the knowledge you guys have on it. Thank you for helping me to tackle jobs that a couple years ago I would have no question about it, taken to a garage and paid hundreds of dollards to fix!!!

I'm curious how many people have simply shortened bolts and used same plate, new gasket vs how many have gone to a 1/4" plate and new gasket.
I seem to think that either option is just as good when installed correctly? Agreed? As long as your steel plate is flat. Any thoughts from you guys on that?

 

this is a good point but I think its not really an issue due to the negative pressure actually sucking the plate against the gasket....I think the metal ridge where the metal plate bumps out addresses the rigidity along that path which is shared by the gasket.
As far as the TSB...I was told about it ironically by the Dodge dealer service dept when I went there to pickup a roll bar one of the employees was selling on craiglist....I'll see what I can find in writing But Honestly after thinking about it it may not be there because of grounds for a recall and lawsuits that would follow....Being a field engineer in another field myself I see manufactuers sweep defects like this under the carpet all the time to avoid paying for damages.. My point is if its the problem then its the problem regardless of popular opinion from those who havent tried addressing that issue alone themselves.

When I did a google search on the matter I found many other jeep forums and such suggesting repairing with the washers or shorter bolts... It one of those things were advertising and word of mouth take over and the alternative solutions are lost within a group of people... Logic states if the bolts bottomed out then it should be assumed first that THAT was the issue.... when I address my issues with a bad head this spring I will take another look at my steel plate on my truck which at 150k shows no sign of leaking... Was the issue addressed by a PO? maybe.. Or maybe the holes are deep enough on some to not be a big enough factor to cause all of the plates to fail? The plates are all the same spec its safe to assume the holes are more likely the varying factor from truck to truck...
We already have another thread that has uncovered that a good number of people saw oil (likely from a pvc valve) on the plate and tore it out only to find the gasket was indeed holding up fine...

 

would be curious to know if your hole depths fell on the side of the fence that says, you have a good gasket or if you have an extra washer or a shorter bolt on a stock plate that is not leaking! If word of mouth takeover on the DF had gone down the path of adding a washer or using a shorter bolt, then we wouldn't have an "be all end all plenum thread" on the DF regarding all the business of the aluminum plates. That's too bad b/c the shorter bolts makes much more sense. After seeing the guy with the pic where his gasket was stretched between bolt holes and bulging out the side, I was convinced that compression was a problem more than expansion rates being a problem.

 

i am curious about the canadian vs american assembly lines as i have two 5.9l rams with approx 160k miles on them and no plenum issues so to speak of.