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Outback Jack

Head Gasket selection for 4L SOHC.

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OK, just thought I would put this up for people who were looking at replacing the head gasket on their 4L SOHC motor.

 

There are a few different head gaskets available for the 4L.

From left to right are....

(Left) Endurotec Composite head gasket with silicon embossed seals.

(Centre) Permaseal Composite head gasket.

(Right) Permaseal AU style Multi Layer Steel head gasket with Viton coating.

38534f3279ead07376030ed351ad02c1.jpg

 

The 4L SOHC motor from EA-EL come from the factory with a Composite style head gasket.

3b744dfca739317b2c530b9db77bedc9.jpg

This has steel fire rings around the bore holes and a steel inner layer sandwiched between 2 composite layers.

 

This can also have silicon sealing rings to help with sealing water jackets , oil galleys etc as with this Endurotec Composite head gasket....

dfe4f7ec1595c4f2c4dc066e76ef0df3.jpg

 

The 4L SOHC motor in the AU came from the factory with a Multi Layer Steel (MLS) style head gasket.

This is an aftermarket Permaseal AU style MLS head gasket.....

b01fdb44291375d6f90d000ba5fb0d88.jpg

This is usually 3-5 layers of stainless steel with embossing around all the ports and a rubber/viton layer to help with sealing.

 

Now it is common practice for people to replace the older style factory Composite head gaskets on EA-EL with the AU style Multi Layer Steel (MLS) head gaskets.

This will increase compression on the EA-EL motors as the gasket is thinner and can increase head gasket life and strength for boosted applications.

 

Now if you are rebuilding an engine and have had the head and block faces machined, it's a no brainer.

Switch to the AU style Multi Layer Steel head gasket.

Just make sure you mention to the machinists you want the faces of the head and block to suit, as the MLS head gaskets require a much smoother surface on both faces for correct sealing.

Usually 15Ra-50Ra (up to MAX of 70Ra)

Blocking the surfaces may not even be enough to get a smooth enough surface.

 

Also try to avoid any sealants, install dry.

The coating on the MLS needs to be able to seal by itself and expand and contract with the steel it is bonded to.

 

But what happens if your not able to machine both surfaces?

 

What happens if the head is machined but not the block?

 

What if you have fire ring marks or corrosion marks/low spots?

 

Chances are you won't be able to get the required finish to run an MLS head gasket and get it to seal properly without machining the head and block to suit.

MLS gaskets are less forgiving of surface imperfections.

 

 

This is a block that needed a head gasket replacing. It has been block sanded already, but as you can see, there are still imperfections in the surface.

ca499338dcff05989516b252274f7a3d.jpg

611e1d3000536538e6af0b0381950889.jpg

These include Fire ring marks and Corrosion marks.

edcf6a75e4c9b5e1a5c5947f8657d779.jpg

The block is super smooth but has imperfections.

 

But not to fear.....

 

While machining of the block and head would be the ideal thing to do for a perfect finish, it's not always possible.

 

I suggest at LEAST the head should be machined.......

bdbb68f65d8109507f58e22e28782c17.jpg

And the block then block sanded with fine wet and dry, a lubricant and alternating between 45 degrees one way, then 45 degrees the opposite way with a Large sanding block.

2fbb9d1afa48d5faf9841e66987ab2fd.jpg

a25bf5ad5db40071cbc43f5a9ad438e7.jpg

 

Composite head gaskets are a lot more forgiving than Multi Layered Steel head gaskets when it comes to surface finish.

They can better seal imperfections in the mating surfaces.

They require 30Ra-110Ra, which is a much rougher and wider range.

 

Composite head gaskets with silicon sealing rings can give help with dodgy water port sealing.

This doesn't mean you can just slap them in. Good surface preparation is still required.

 

Composite head gaskets can also hold boost up to about 20psi, so don't worry too much about using them on most N/A applications.

 

Better to have a head gasket that seals properly and works than a fancy one that can't because of imperfect mating surfaces.

 

This is what happens to an MLS head gasket if installed on too rough a finish.....

b1a20b9da69cba8dde00bf718ae0198f.jpg

8530f5297fea8b289c1c26f1e5a84981.jpg

f907345d04e2b3e7fcbcbcc7a859522a.jpg

That was a Permaseal MLS-R head gasket, less than 500km old.

Installed by a 'mechanic'.

 

Also if installing a Permaseal MLS-R head gasket to an EA-EL motor, check the rivet on the rear of the gasket doesn't foul and get stuck between the head and block.....

bdd69f09526a40a3edf46ae4da03fb8b.jpg

31663c854f566eb8dd1cffed69fdf98a.jpg

4a129e5e51fe3ce9452b57d702a9c6c3.jpg

The permaseal MLS-R has rather large rivets, the one on the rear will foul. The permaseal MLS has smaller rivets but I would still check the clearance.

Just a couple of things to keep in mind if deciding to go the MLS route.

 

 I could install another MLS head gasket but chances are it would fail again due to surface roughness.

 

My Composite head gasket lasted 300,000km from the factory before it failed, so if installed properly it will last.

I will leave the MLS until everything is machined properly to suit it on the next rebuild......

 

 

Happy Head Gasketing!

 

Outback Jack.

 

 

 

 

 

 

 

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Nice write-up there Jack. I think your factory one may have lasted as long as it did due to less heating/cooling cycles throughout those km travelled, being a country car and all. Most suburban/city cars would have their head gasket let go anywhere from 150k to 250k.

It also helps if you keep the cooling system up to scratch and never let it cook. As little as one instance of overheating and the damage is done (warped head, broken head bolt, corroded bolt and/or surrounding gasket).

In my EF, once I was stuck in traffic on the Cahill Expressway (coming onto Harbour bridge) and the radiator tank exploded. I pulled up immediately but I think somehow the fans didn't come on before that. So that made it run hot and boil over/blow a radiator.

Another time, I blew a heater hose on the M7 going to work without knowing, and only found out I'd run it dry when I pulled up at the bottom of the exit ramp with the engine locking up. I managed to cool it back down while running back and forth to a nearby creek to get some water. I tried putting some in and it was that hot, it boiled straight back out at me. Once I finally got some water in it, I heard an audible "click" and I reckon that was a head bolt snapping. From that point on, the motor just didn't have the same pep it used to, and it used coolant fairly quickly.

An all-iron motor would have none of these issues... A major downside of running an alloy head and iron block together, coupled with the fact that these heads are pretty big, amplifying the expansion difference between the metals.

I can see why Ford finally went with an MLS gasket. They let the two metals "slide" over each other as one expands in relation to the other, while still managing to seal.

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an alternative to wet&dry to smooth the deck is a combonation stone, I recently brought my bro a new one for work (mechanic),

I get them cheaper through my work, Norton/Bear large (230mmx80mm) silicon carbide stone.

 

 

 

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Nice write-up there Jack. I think your factory one may have lasted as long as it did due to less heating/cooling cycles throughout those km travelled, being a country car and all. Most suburban/city cars would have their head gasket let go anywhere from 150k to 250k.

It also helps if you keep the cooling system up to scratch and never let it cook. As little as one instance of overheating and the damage is done (warped head, broken head bolt, corroded bolt and/or surrounding gasket).

In my EF, once I was stuck in traffic on the Cahill Expressway (coming onto Harbour bridge) and the radiator tank exploded. I pulled up immediately but I think somehow the fans didn't come on before that. So that made it run hot and boil over/blow a radiator.

Another time, I blew a heater hose on the M7 going to work without knowing, and only found out I'd run it dry when I pulled up at the bottom of the exit ramp with the engine locking up. I managed to cool it back down while running back and forth to a nearby creek to get some water. I tried putting some in and it was that hot, it boiled straight back out at me. Once I finally got some water in it, I heard an audible "click" and I reckon that was a head bolt snapping. From that point on, the motor just didn't have the same pep it used to, and it used coolant fairly quickly.

An all-iron motor would have none of these issues... A major downside of running an alloy head and iron block together, coupled with the fact that these heads are pretty big, amplifying the expansion difference between the metals.

I can see why Ford finally went with an MLS gasket. They let the two metals "slide" over each other as one expands in relation to the other, while still managing to seal.

Sent from my CPH1920 using Tapatalk


Yeah my factory gasket has lasted a fair while but I maintain my cars pretty well.
Always checking for leaks etc, regular servicing, quality lubricants and filters.
Country driving helps.

Ford went the MLS route for just that reason. They raised the compression on the AU motor, so it was a logical step.
The MLS gaskets are better at sealing 2 different metals like Alloy and Steel.
They can handle detonation better and resist 'lift' by the alloy head at operating temps.
I would be using one if the block finish was better, but block sanding is not machining and I don't want to create an uneven surface.





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an alternative to wet&dry to smooth the deck is a combonation stone, I recently brought my bro a new one for work (mechanic),
I get them cheaper through my work, Norton/Bear large (230mmx80mm) silicon carbide stone.
 
 
 
Never tried that Ford Man, I use wet and dry so I can start off about 400 grit, then 600 grit , then 800 grit.
I probably don't apply enough pressure when sanding, but like to go on the cautious side.

I'd still like to use an MLS gasket but the last one cost me $450 and it left a bad taste in my mouth having to throw it because it was toast.
I'm not sure I can get the finish it requires.

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On 1/10/2021 at 2:46 PM, Outback Jack said:

OK, just thought I would put this up for people who were looking at replacing the head gasket on their 4L SOHC motor.

 

There are a few different head gaskets available for the 4L.

From left to right are....

(Left) Endurotec Composite head gasket with silicon embossed seals.

(Centre) Permaseal Composite head gasket.

(Right) Permaseal AU style Multi Layer Steel head gasket with Viton coating.

38534f3279ead07376030ed351ad02c1.jpg

 

The 4L SOHC motor from EA-EL come from the factory with a Composite style head gasket.

3b744dfca739317b2c530b9db77bedc9.jpg

This has steel fire rings around the bore holes and a steel inner layer sandwiched between 2 composite layers.

 

This can also have silicon sealing rings to help with sealing water jackets , oil galleys etc as with this Endurotec Composite head gasket....

dfe4f7ec1595c4f2c4dc066e76ef0df3.jpg

 

The 4L SOHC motor in the AU came from the factory with a Multi Layer Steel (MLS) style head gasket.

This is an aftermarket Permaseal AU style MLS head gasket.....

b01fdb44291375d6f90d000ba5fb0d88.jpg

This is usually 3-5 layers of stainless steel with embossing around all the ports and a rubber/viton layer to help with sealing.

 

Now it is common practice for people to replace the older style factory Composite head gaskets on EA-EL with the AU style Multi Layer Steel (MLS) head gaskets.

This will increase compression on the EA-EL motors as the gasket is thinner and can increase head gasket life and strength for boosted applications.

 

Now if you are rebuilding an engine and have had the head and block faces machined, it's a no brainer.

Switch to the AU style Multi Layer Steel head gasket.

Just make sure you mention to the machinists you want the faces of the head and block to suit, as the MLS head gaskets require a much smoother surface on both faces for correct sealing.

Usually 15Ra-50Ra (up to MAX of 70Ra)

Blocking the surfaces may not even be enough to get a smooth enough surface.

 

Also try to avoid any sealants, install dry.

The coating on the MLS needs to be able to seal by itself and expand and contract with the steel it is bonded to.

 

But what happens if your not able to machine both surfaces?

 

What happens if the head is machined but not the block?

 

What if you have fire ring marks or corrosion marks/low spots?

 

Chances are you won't be able to get the required finish to run an MLS head gasket and get it to seal properly without machining the head and block to suit.

MLS gaskets are less forgiving of surface imperfections.

 

 

This is a block that needed a head gasket replacing. It has been block sanded already, but as you can see, there are still imperfections in the surface.

ca499338dcff05989516b252274f7a3d.jpg

611e1d3000536538e6af0b0381950889.jpg

These include Fire ring marks and Corrosion marks.

edcf6a75e4c9b5e1a5c5947f8657d779.jpg

The block is super smooth but has imperfections.

 

But not to fear.....

 

While machining of the block and head would be the ideal thing to do for a perfect finish, it's not always possible.

 

I suggest at LEAST the head should be machined.......

bdbb68f65d8109507f58e22e28782c17.jpg

And the block then block sanded with fine wet and dry, a lubricant and alternating between 45 degrees one way, then 45 degrees the opposite way with a Large sanding block.

2fbb9d1afa48d5faf9841e66987ab2fd.jpg

a25bf5ad5db40071cbc43f5a9ad438e7.jpg

 

Composite head gaskets are a lot more forgiving than Multi Layered Steel head gaskets when it comes to surface finish.

They can better seal imperfections in the mating surfaces.

They require 30Ra-110Ra, which is a much rougher and wider range.

 

Composite head gaskets with silicon sealing rings can give help with dodgy water port sealing.

This doesn't mean you can just slap them in. Good surface preparation is still required.

 

Composite head gaskets can also hold boost up to about 20psi, so don't worry too much about using them on most N/A applications.

 

Better to have a head gasket that seals properly and works than a fancy one that can't because of imperfect mating surfaces.

 

This is what happens to an MLS head gasket if installed on too rough a finish.....

b1a20b9da69cba8dde00bf718ae0198f.jpg

8530f5297fea8b289c1c26f1e5a84981.jpg

f907345d04e2b3e7fcbcbcc7a859522a.jpg

That was a Permaseal MLS-R head gasket, less than 500km old.

Installed by a 'mechanic'.

 

Also if installing a Permaseal MLS-R head gasket to an EA-EL motor, check the rivet on the rear of the gasket doesn't foul and get stuck between the head and block.....

bdd69f09526a40a3edf46ae4da03fb8b.jpg

31663c854f566eb8dd1cffed69fdf98a.jpg

4a129e5e51fe3ce9452b57d702a9c6c3.jpg

The permaseal MLS-R has rather large rivets, the one on the rear will foul. The permaseal MLS has smaller rivets but I would still check the clearance.

Just a couple of things to keep in mind if deciding to go the MLS route.

 

 I could install another MLS head gasket but chances are it would fail again due to surface roughness.

 

My Composite head gasket lasted 300,000km from the factory before it failed, so if installed properly it will last.

I will leave the MLS until everything is machined properly to suit it on the next rebuild......

 

 

Happy Head Gasketing! Top Stuff Indeed Good Value !

 

Outback Jack.

 

 

 

 

 

 

 

 

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