Aluminum vs steel valve covers

[jeepman3071]

Jeep 4.0Ls are known to be noisy engines, between piston slap and valve train noise, they make their own symphony of sounds.

My Jeep came with an aftermarket aluminum valve cover when I bought it. The stock cover for this engine is made out of stamped steel. My friend has an almost identical Jeep, same year and engine with about 10k less miles. His seems to have less valve train noise than mine, and he has the stock stamped steel cover.

My previous Jeep also had the steel cover and seemed quieter. I know aluminum helps dissipate heat better, but what material is a better sound barrier?

 

[Corvette Owner]

I think steel is, it is more dense.

The OEM valve covers on my 1964 Corvette were aluminum. I had solid lifters which needed many adjustments, the aluminum valve covers eventually cracked and leaked oil.

The steel replacements didn't seem much quieter though, so don't expect much difference.

 

[jeepman3071]

Originally Posted By: Corvette Owner
I think steel is, it is more dense.

The OEM valve covers on my 1964 Corvette were aluminum. I had solid lifters which needed many adjustments, the aluminum valve covers eventually cracked and leaked oil.

The steel replacements didn't seem much quieter though, so don't expect much difference.


Thanks for the info. The reason I ask is that the bolts keep loosening on the aluminum cover and causing leaks. I might pick up a steel one if the bolts will stay tight and figured if it also helps deaden sound slightly its an added bonus. Every little bit helps with these engines.

 

[OVERKILL]

Originally Posted By: jeepman3071
Originally Posted By: Corvette Owner
I think steel is, it is more dense.

The OEM valve covers on my 1964 Corvette were aluminum. I had solid lifters which needed many adjustments, the aluminum valve covers eventually cracked and leaked oil.

The steel replacements didn't seem much quieter though, so don't expect much difference.


Thanks for the info. The reason I ask is that the bolts keep loosening on the aluminum cover and causing leaks. I might pick up a steel one if the bolts will stay tight and figured if it also helps deaden sound slightly its an added bonus. Every little bit helps with these engines.


ARP valve cover studs. Problem solved.

Though depending on what gasket you are using, that may be the issue. I know for the 5.0L Ford's, there are gaskets that have metal inserts where the holes are, so once tightened down the gasket doesn't continue to compress in that area causing the fastener to loosen. I THINK these were made by Felpro?

 

[jeepman3071]

The gasket is a FelPro. The valve cover gasket on this era 4.0L is a rubber reusable one. The gasket seals fine when the bolts are tight, but they eventually loosen and the gasket begins to leak oil. According to the Jeep forums this is a common issue with this valve cover. I also don't like the oil cap that it came with. Its literally a little rubber plug that gets pressed into the cover. I'm more of a screw on oil cap guy.

 

[Loobed]

What type of aluminum covers?

They have the stamped thin sheet aluminum type (Moroso), and the thicker cast aluminum. The thicker cast aluminum covers are better at deadening the sound. The thin steel and aluminum covers act like a bell.

 

[jeepman3071]

Originally Posted By: Loobed


What type of aluminum covers?

They have the stamped thin sheet aluminum type (Moroso), and the thicker cast aluminum. The thicker cast aluminum covers are better at deadening the sound. The thin steel and aluminum covers act like a bell.



This cover isn't very thin, so I believe it is cast aluminum. It is manufactured by Crown Automotive.

 

[1345]

Originally Posted By: jeepman3071
The gasket is a FelPro. The valve cover gasket on this era 4.0L is a rubber reusable one. The gasket seals fine when the bolts are tight, but they eventually loosen and the gasket begins to leak oil. According to the Jeep forums this is a common issue with this valve cover. I also don't like the oil cap that it came with. Its literally a little rubber plug that gets pressed into the cover. I'm more of a screw on oil cap guy.

Did you replace all of those gromets that came with the gasket?

 

[jeepman3071]

Originally Posted By: 1345
Originally Posted By: jeepman3071
The gasket is a FelPro. The valve cover gasket on this era 4.0L is a rubber reusable one. The gasket seals fine when the bolts are tight, but they eventually loosen and the gasket begins to leak oil. According to the Jeep forums this is a common issue with this valve cover. I also don't like the oil cap that it came with. Its literally a little rubber plug that gets pressed into the cover. I'm more of a screw on oil cap guy.

Did you replace all of those gromets that came with the gasket?



This cover doesn't use the grommets. It just uses bolts.

 

[mechtech2]

The nut on a stud is likely to loosen just as much as a bolt.
Gasket compression and soft aluminum are likely to cause this.
If they are loosening or compressing, just remember to tighten them as needed.

 

[artificialist]

Would using light threadlocker help?

 

[jeepman3071]

Originally Posted By: artificialist
Would using light threadlocker help?


I thought about that. A friend has an extra steel cover in great shape so I might just paint that one and throw it on.

 

[440Magnum]

There are a couple of simple things to remember when trying to contain noise with a barrier of any sort.

1) Mass per unit area is the biggest factor. That's why a drywall and plaster in apartment complexes or offices block noise better than plywood, paneling, etc. This is also why Dynamat and similar materials work so well. They are both heavy and acoustically "soft" (see number 2 below).

2) Bonding materials with different acoustic impedances (think "hard" and "soft") together in a single barrier is better than a single-layer barrier, even if the mass per unit area is the same.

3) "Fuzzy" barriers don't do that much, but they are still useful. They reduce echoes back into the noisy area, but don't do all that much as far as preventing noise from passing through. So a very good sound barrier is a fuzzy layer to deaden echoes and absorb sound energy, a hard/heavy layer bonded to a soft/heavy layer to reflect as much sound back into the fuzzy/absorptive layer as possible.

#2 is probably what makes a stock Jeep valvecover quieter than an aluminum one. The factory "paint" is probably an elastomer compound (I KNOW it is on 1993 and later Chrysler v6 engines, and it looks like it on my two 4.0's), and that acoustically "soft" layer bonded to the metal helps a lot. Especially with high-frequency "clattery" sound like happens under the valve cover.

 

[Kestas]

I remember 30 years ago the auto company I was working at was toying with the idea of making steel oil pans and valve covers out of sandwiched steel, to help keep engine noise down. The steel had plastic sandwiched between two sheets of steel.

 

[OVERKILL]

Originally Posted By: mechtech2
The nut on a stud is likely to loosen just as much as a bolt.
Gasket compression and soft aluminum are likely to cause this.
If they are loosening or compressing, just remember to tighten them as needed.


That hasn't been my experience, at least with the ARP studs.

 

[mechtech2]

Overkll=
Why would a nut hold better than a bolt? Assuming the same thread pitch,they would be the same. The bolt should have more area on the threads, and possibly be superior.
What magic is there is a stud?
Neither can help with gasket compression or aluminum deformation.

440-
Dynamat attenuates sound by dampening the vibration of panels. It doesn't block sound, even though many try to misuse it this way.
25% or so of a panel is what should be used.

 

[ag_ghost]

Originally Posted By: mechtech2
Overkll=
Why would a nut hold better than a bolt? Assuming the same thread pitch,they would be the same. The bolt should have more area on the threads, and possibly be superior.
What magic is there is a stud?
Neither can help with gasket compression or aluminum deformation.

Excerpt from page 37 of the current ARP (on arp-bolts dot com) catalog, albeit it is referring to cylinder head fasteners in contrast to valve covers, fwiw:
"...On many street-driven vehicles, where master cylinders and other items protrude into the engine compartment, it’s probably necessary to use head bolts so that the cylinder heads can be removed with the engine in the car. For most applications, however, studs are recommended. And for good reason.... Studs also provide more accurate and consistent torque loading. Here’s why. When you use bolts to secure the head, the fastener is actually being “twisted” while it’s being torqued to the proper reading. Accordingly, the bolt is reacting to two different forces simultaneously. A stud should be installed in a “relaxed” mode – never crank it in tightly using a jammed nut. If everything is right, the stud should be installed finger tight. Then, when applying torque to the nut, the stud will stretch only on the vertical axis. Remember, an undercut shorter stud will have a rate similar to a longer, standard shank stud. This provides a more even clamping force on the head."

 

[MarkM66]

A stud red loctite'd in with a locking nut. It's not going anywhere,

.

 

[OVERKILL]

Originally Posted By: mechtech2
Overkll=
Why would a nut hold better than a bolt? Assuming the same thread pitch,they would be the same. The bolt should have more area on the threads, and possibly be superior.
What magic is there is a stud?
Neither can help with gasket compression or aluminum deformation.

440-
Dynamat attenuates sound by dampening the vibration of panels. It doesn't block sound, even though many try to misuse it this way.
25% or so of a panel is what should be used.



Well for starters, they don't have the same thread pitch. The part of the stud going into the head obviously does, but the top part that the nut screws on has much finer threads.

Those are the ones I used on my 302.

 

[andyd]

Wabbout using a toothed washer?