Silicon head gasket questions

[Gen3AntiqueAuto]

Says in Langs that it "will not work with the z head" - anyone know why?
What about working with the Prus head (also aluminum)?
Anyone measured the thickness of that vs copper?

"Premium silicone head gasket. This head gasket has a solid steel core inside heavy-duty high density gasket material coated with silicone and high temperature silicone around all water passages. Install with NO additional sealants. This will not work with "Z" high compression heads part 3001H-14 or 3001HCH."

[TXGOAT2]

Is that the gasket with silicon beads on it?
I don't know why it wouldn't work, but I'd take their word for it.
I have a Z head, but I don't have a Ford head or block that's apart to compare it to.
I have a Fel Pro "blue" head gasket that I hope will work with the Z head.

[Henry K. Lee]

It has to do with where the fire ring crimp is on the head side of the head gasket.., it may prematurely fail.

Hank

[Jerry VanOoteghem]

A guy in our chapter used the silicone gasket with a Z head twice. He had it fail... twice. Don't do it.

[Joe Bell]

I have one hanging on a nail in the barn to show where the seal let loose.

[John Illinois]

Model A folks have had trouble with the silicone gasket for years. They leak water on the side or fail. I had one once,not an improvement .

John

[Gen3AntiqueAuto]

Thank you kindly - no silicone.......

[TMiller6]

Add my name to the list of Model A owners who will never use the steel/silicone head gasket again. On paper it sounded like a good idea; my crankcase told me otherwise.

[John iaccino]

I had a silicon head gasket fail. Went back to Copper with copper coat. Copper has been around for 100 yrs.

[Allan]

The failures on Z heads may be due to the inconsistent shape of the combustion chambers. Some gaskets fit well, others reveal work needed to match the chambers to the gasket. Prus heads seem to be far more precisely cast.

Allan from down under.

[Kevin Pharis]

Sounds like I’m the outlier this time…

Modifying copper laminated head gaskets for oversized valves is a PITA, so I started making and running solid copper. Solid gaskets work good… but they would typically start weeping after a few years. I eventually tried one of the modern type silicone gaskets. The fire ring was easily removed and reshaped for the larger valve clearance. While the fire ring was out, the panel was easily trimmed with tin snips to the desired shape. And reassembling the fire ring is a snap. Could probably modify 5 of these in the time it takes to modify 1 copper laminated gasket.

Once installed, I found these gaskets performed very well and held water reliably. My only dislike was that they are not reusable. They will need to be scraped off when removed. It is critical with this type gasket that the fire ring is in good contact with the block and head, and the head and block must be properly surfaced and clean when assembled

[TXGOAT2]

Has anyone successfully used a Fel Pro 7012 B "blue" head gasket with a Z head? Block is bored .060.

[Susanne]

I ran the copper sandwiches for years (bare, no coating) and they worked just fine... I was also always fond of the solid copper gaskets, only issue was you'd have to re-anneal them before reassembly and again every so often as they work harden and can seep... The one gasket I depsised and after having 2 fail back to back and almost immediately were those silly-cone ones... these on low head motors. Kind of like those flat manifold gaskets - IDK why they even sell them, but some people swear by them, while I swear AT them...

[mbowen]

…Copper has been around for 100 yrs.

Except when I needed a couple early last year. My only choice was silicone, one just to get me through the touring season while waiting to get on a shop’s overhaul schedule. I ran it for 1500 miles with no issues before pulling the engine for overhaul. The other has only been driven a couple hundred miles but is not showing any issues. BTW, both were for stock Ford heads, and were installed per included instructions.

[Craig Leach]

I'm with Miles. During the copper head gasket famine, silicone & steal where the only options. Some of us doomsday preppers purchased
the silicone head gaskets so we would at least have something to work with. As far as I can tell the biggest issue is with aftermarket aluminum
high compression heads. Has anyone had issue with them with stock heads. This seems to be the preferred style for modern engine rebuilders
other than for high performance, supercharged & NOX race applications with combustion pressures that will drive the crank out the bottom
of a T engine. Joe you said you have one hanging on a nail to remind you. Was that with a Z head? do you have picks? In my infancy with model
T's I used them and don't remember ever having trouble with them other than they are a pain to clean off when you remove the head for other
repairs.
Craig.

[cslandry]

I really like the copper gaskets but, when they were unavailable, I put in one of the silicone ones. (stock head) It's been 3500 miles with no issues. I'll probably go back to copper the next time the head has to come off, but I can't complain.

[DanTreace]

".Joe you said you have one hanging on a nail to remind you. Was that with a Z head? do you have picks? In my infancy with model
T's I used them and don't remember ever having trouble with them other than they are a pain to clean off when you remove the head for other
repairs."
Craig.


These pics came off the forum a time ago. IMO the tiny bead of silicone can't really be relied upon for combustion sealing and water port sealing, there is only a very small thin narrow bead of silicone. And IMO, but never used one, think this modern silicone bead gasket is stiff and can't compress like the sandwich copper clad gaskets. The squish of a gasket when torqued, and with a good sealant on both sides the copper clad gasket insures best safety and long use. Of course proper sequences to compress from the center of the head and out to sides and ends helps to reduce failure between the cylinders where gap is tiny.

Seems failure in this example is with the water ports, where seal of tiny ring of silicone was imperfect, and water invaded a cylinder. Z- type head, but think this is more like the Ricardo head, with that compression chamber ridge.