So I got done doing my friends Dad's 360 plenum gasket today (about my 10th time doing this dance on a magnum motor) and in doing so I've thought of some things and realized the one thing I've noticed on all of the magnum plenums I've done is that the gasket sticks to the steel plate each and every time and never to the aluminum and the gasket is a bitch to clean it off the steel plate and that cleaning is generally the most time consuming part of the plenum job which is so crucial to the success of the plenum job.

So during all this heat expansion the leak is actually happening between the aluminum intake and gasket not between each side of the gasket. When cleaning the gasket off of the steel plate it seems nearly impossible even with a wire wheel grinder to remove the gasket from the steel plate.

So there are two ways to fix our plenum issue if anyone is interested in reading my take on the pros and cons of each fix.

Popular Fix: Hughes Plenum Plate.

Pros: *"Should" solve the problem*, Less clean up time due to lack of having to clean the stubborn gasket off of the old steel plate, less electricity used powering an air compressor which in turn powers an air wire wheel grinder or electric grinder when used for cleaning the plenum plate.

Cons: *"Should" Fix The Problem*. I've heard of these gaskets still failing even with the Hughes plate and frankly "should fix it" isn't good enough for me as the gasket itself is part of the plenum blow out problem. Plus if I had an aluminum plate I'd end up permatexing it anyway in which case I mine as well use method #2 alone (Below this paragraph) and save myself some money. Also its very expensive at $120.

Copper Permatex Fix: Copper Permatex is applied to each side of the provided Felpro Plenum Gasket.

Pros: Cheap,Extremely effective, Ensures Cushion for the gasket & allows room for heat expansion and stretching with the steel plate. It also doesn't allow the gasket to stick to the steel plate preventing the leverage that breaks the gasket. Also regardless of if your plenum plate bolts are too long and bottom out, the permatex will still seal the small gap left behind!.

Cons: Takes more time to apply and can be messy. Saves time- Steel plenum plate clean up on average takes 15-20 minutes, sometimes a half hour if your tools don't cooperate!.

Personally I'll go with the copper permatex method any day of the week, but I thought I'd list the pros and cons as I know them for people to decide themselves on what they would prefer to do.

 

No sealant is required with the updated Fel-Pro - Plenum Gasket Set (Part # MS95462) that is available. Where did you find this information where you reached your conclusion?

 

"No sealant is required"

Doesn't mean you can't use some!

 

Have you even seen the Fel-Pro gasket? If you did, you wouldn't have made that statement.

 

Most of the post-fix failures were due to mis-installation. If you don't torque things properly, in the correct sequence, you are going to get the opportunity to do it again. Also depends on the quality of gasket you use. I really didn't like the one hughes sent with their kit........ I bought the fel-pro gasket, and don't have a problem.

 

Ditto.

I thought I had another leak after doing the Hughes fix because there was a light coating of oil inside the intake but that turned out to be a little oil coming through the PCV valve.

 

I got my Felpro Intake set from O'Reillys for $22, it came with intake gaskets,plenum gasket & front & back cork intake gaskets.

Frankly its just experience in putting so many on. I've got 10 of them under my belt now and personally I think the gaskets that need the permatex on them the most are the felpro ones, as they typically just blow out the sides while the stock ones usually will stay stuck & baked on to the steel plate unless the stock gasket failed early on in its life then you will see an actual blow out.

Regarding the Hughes plate, I think the Hughes plate is nice if you can get it or a copy of it cheap enough, overall for the average Ram owner I think that its not needed. No sealant is required on intake gaskets either but yet I still slap a thin layer of rtv or permatex on at least around the water inlets, just to be sure, as I don't want to be doing the job again. But with that said I'm impressed with the quality of the stock gaskets, the last 4 or 5 magnum motors I've worked on the intake gaskets came off clean and in one piece! So clean that in a post apocalyptic situation you could have reused them!.

The main problem with the steel plate moving & expanding/contracting at a different rate than the aluminum is that the gasket always seems to stick to the steel plate (as mentioned earlier) and thus when the steel plate expands it will pull the gasket off the aluminum plenum causing your leak. The permatex fix regardless of the plate or gasket used will not allow the felpro gasket to stick to either surface reducing the surface tension that pulls gaskets apart, it allows freedom of movement and it takes up most imperfections in both the steel plate and aluminum plenum.

So even if the plenum does expand the permatex will expand with it and always seal (given that you have both the intake and steel plate clean enough to eat off of and grease/oil free!). It also takes up the space left behind by a less common issue of factory bolt holes not being tapped deep enough. The good feeling is when you torque it down and see permatex come out the sides you know you've got a seal. I put a nice coat on each side of the felpro gasket, but not too much as to make a messy job.

Most likely the next plenum I'm doing is my parents 1992 Dodge Van with a 318 Magnum, it has 330,000 miles on it! I'm both scared and excited to see what that gasket looks like as its never had ANY engine work done!. The motor oddly idles as smooth as my 360 and has A LOT of power still for a 21 year old 318 with that many miles.

 

I'm not completely knocking your permatex concept, however, I am knocking you for not providing pictures of your "tried and true" method. You could be carrying alot more credibility with such demonstration of all 10 or w/e number. Especially sharing in this thread here for people -- https://dodgeforum.com/forum/2nd-gen...ost-up-13.html

Right now you just read like a stuck up 21 yr old. Sorry buddy, that's just how you come across, even though I get your concept. It might also be why others respond in the manner shown.

I'll definitely disagree with the notion that there is an amount of differential expansion contributing as the root of the problem. Plenty of other threads that have discussed this in the past. A good few people have also do some basic deflection calcs - deflection = E*alpha*deltaT for example.

Get some pictures up and a step by step to show your shiz bud! At least you can show it is ONE option for people to choose from.

 

From an engineering standpoint, depending on the steel used for the OEM plate, I estimate any "expansion" to be limited to apprximately 0.0003" at a maximum, and that would be a lateral expansion and not bowing away from the mating surface. Don't think that would cause a gasket failure imho.....

 

An aluminum plate with the FelPro gasket requires zero sealant. The gasket has a sealant bead built into it.