This doesnt mean it "Needs" replacing...this is unfortunatly a common myth repeated here. The fact that the stock plates were steel has not been proven to cause any problems... all the evidence points to the fact that the stock bolts were too long and bottomed out before applying enough pressure to compress the gasket enough to hold it in place....(this was confirmed as the problem in a dodge TSB)

That said there's nothing wrong with upgradinging to a thicker aluminum one especially if your going to be pushing some serious air through there with a turbo or something, but there really hasnt been any issues with a steel plate actually cracking or failing / not holding up either so...

 

The #8 and #5 plugs will show signs of oil fouling due to the oil from a bad gasket being sucked into the runners because with the engine being tilted down it the back the oil pools up in the back of the intake.

 

Well, that piece of information was left out. I stand corrected that the plenum is not necessarly bad.

Pull the air cleaner again, climb on top of your motor (carefully), use a flashlight and look at all possible areas in the plenum. Look for oil pooling anywhere other that directly under the TB. Use a small mirror if you have to. Doing this will give you a better idea of whether or not it's good.

 

If you're losing 1.5 qt/1K then you have one of 2 problems...a blown belly pan gasket or a totally worn out engine. If it were the worn out engine it would be smoking out the tail pipes like a freight train.

 

For the love of God, How many more plenum related threads do we need to post??? LOL

It's not like the info is hard to find since it's right next to the "new thread" button. Jeez. Whatever!

 

Apparently it's some number X, where X << STFW << STFU.

 

I would agree that the truck runs too good to be a busted engine but regardless, the plenum fix costs: time with in my friends garage on a 15 acre farm and some CNC machining at my shop! So I'll try the fix it for free route and if that don't stop it from drinking oil like moonshine then I'll head to the junkyard and buy another motor to put it in! I will probably post a couple more plenum threads before I go to the junkyard! Thank you dodge for causing zman to have high blood pressure over plenum posts.
For all you guys that have been so helpful and friendly, if you ever need some minor machining done like a plenum plate or something I'm willing to barter some services on a HAAS cnc mill (mat'l included if it's 6061 or another common material we have laying around for scrap) in exchange for a few tools or something.
I'm getting ready to machine another plenum plate for someone on the forum when I machine mine as soon as I get the gaskets! I use solidworks/mastercam and HAAS milling machines so I can pretty much draw/machine anything you want so long as it's small enough to carry out in one hand. Bartering is a good thing! thanks again!

 

just pulled plug #8 and it has oil all over the threads. I read the plenum posts and all I see is plug 8 can foul with clogged cat. Is it possible that oil is leaking above the vavle cover gasket and leaking around the plug? I didn't see a lot of oil on the end of the plug but it was caked carbon around the spark end of the plug. I'll pull the throttle body and get a better look at the plenum on the inside to see if a lot of oil is in the back of the plenum. I also took the pcv valve out and it still rattles so I assume that it still works since it valve is loose in the elbow. would oil collect in the plug port due to a clogged cat? I'm concerned about this and haven't seen this in any of the plenum symptoms on this forum. I also don't hear any pinging and never have to shift out of 4th gear going up hills so I don't have a drastic power problem.

 

sounds like you do indeed have the symptoms of a blown plenum gasket...FYI a rattling pvc does not mean its still good...thats another myth...if it doesnt rattle yes its likely bad but even worn out sticking ones usually rattle when you shake them... mine did.

 

Oil on the plug may indeed be from the valve covers..... have a look, see if they are leaking. Is there a fair bit of ash deposits on the plug around the electrode?