silicone head gaskets

[Dr Foot]

I'm about to install a new head gasket using a mild high compression head. Has anyone had any experience using silicone head gaskets. What should be used as gasket sealer to assure no leaks. The head has just been resurfaced.

[DJ S]

Please save yourself the trouble and throw that gasket away. There are plenty of people who have had bad experiences with that head gasket, including myself.

Instead, use Best Gasket Part #509G/ snyders Part #B-6051-XO with a light application of Permatex copper spray (part# 80697).

[Gary WA]

Originally Posted by Dr Foot

I'm about to install a new head gasket using a mild high compression head. Has anyone had any experience using silicone head gaskets. What should be used as gasket sealer to assure no leaks. The head has just been resurfaced.

I agree with #2,! Copper and spray the only way to go.

[Flathead]

Originally Posted by Dr Foot

I'm about to install a new head gasket using a mild high compression head. Has anyone had any experience using silicone head gaskets. What should be used as gasket sealer to assure no leaks. The head has just been resurfaced.

Nobody seems to have any luck with these gaskets. That being said I have one on my A with a 5.5 Snyder head and no problems.
These gaskets DO NOT use sealer and surfaces must be clean, dry, and flat. Dry means no water and no oil or grease residue. Copper or graphite gaskets are probably easier to install.

[JayJay]

I tried the silicone head gasket and no joy. Complete success with the gasket combo DJ S describes in post #2.

Berts has the same gasket (Best 509G) as part #A-6051-BA. The Permatex copper spray you can pick up at your local NAPA or other auto parts store.

[BRENT in 10-uh-C]

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As mentioned above, there are bad experiences with these gaskets however it is not the gasket's fault ...but instead is the mechanic. You cannot install these on surfaces with a rough finish. I have used these with great results. If your head and block decks have a RA finish of 50 or less, then these gasket seal well.

[Keith True]

I've used them.I have a Brumfield head riding on one,I believe it was put on around 02 or 03.At the time Mr.Brumfield had not had much credible feedback with them,so he was leaning against them.He was curious as to how mine would work out,and wanted me to let him know.He also knew that if it failed I wasn't going to whine to him about it.I did see a couple of defective ones,and replaced a couple more.Those I blamed on incorrect installation.They didn't follow the directions.They used a sealer.That negated the whole idea of the silicone rings and the sticky sealer on the surface.Both of those blew a piece out directly under the water pump.There is no pressure there,but the sealer acted as a lube while mounting and let the composite material squeeze right out when the head was being torqued down.

[Jim Brierley]

I recommend the Best 509 copper, but I do not recommend Copper Coat as it never dries, so stays a bit slippery. I use silver spray paint, first a thin coat, let dry, then a heavier coat, dry until tacky and install. The paint acts a little like glue, which I like. The Best graphite is also good but is more difficult to remove when necessary.

[DJ S]

Originally Posted by BRENT in 10-uh-C

As mentioned above, there are bad experiences with these gaskets however it is not the gasket's fault ...but instead is the mechanic. You cannot install these on surfaces with a rough finish. I have used these with great results. If your head and block decks have a RA finish of 50 or less, then these gasket seal well.

Glad to hear you had good luck with your installations. I however did not and it was not the mechanics fault.

I followed the directions, no sealer. Re-surfaced block and head. After 5k mi, I ended up with a combustion gasses in the cooling system and red silicone in the radiator.

I think we can all agree the failure rate is quite high with this gasket (Snyders Part #A-6051-M) and it is prudent to advise against the use of it.

[Dr Foot]

Thank you all. I guess I'll go copper.

[JayJay]

Originally Posted by BRENT in 10-uh-C

As mentioned above, there are bad experiences with these gaskets however it is not the gasket's fault ...but instead is the mechanic. You cannot install these on surfaces with a rough finish. I have used these with great results. If your head and block decks have a RA finish of 50 or less, then these gasket seal well.

I was unaware of the requirements for finish quality, but it certainly makes sense. In my case it was a freshly decked head and a freshly stoned block but still leaked. Replaced with the copper-treated graphite and no issues.

Jim Brierley makes a good point. If you use the copper spray on the graphite gasket it does stay tacky and is a bear to remove. I've had to pull heads twice after installing that way and the graphite gaskets split down the middle, had to scrape both the head and the block. Copper gasket is definitely easier to remove. On the other hand, hopefully when we install a head gasket it's for keeps.

[BRENT in 10-uh-C]

Originally Posted by JayJay

I was unaware of the requirements for finish quality, but it certainly makes sense. In my case it was a freshly decked head and a freshly stoned block but still leaked. Replaced with the copper-treated graphite and no issues.

Jim Brierley makes a good point. If you use the copper spray on the graphite gasket it does stay tacky and is a bear to remove. I've had to pull heads twice after installing that way and the graphite gaskets split down the middle, had to scrape both the head and the block. Copper gasket is definitely easier to remove. On the other hand, hopefully when we install a head gasket it's for keeps.

I lean more to the mindset that I thought people knew. In a nutshell, this modern technology gasket needs modern technology machine work. I use a CBN cutter on my Surfacer which produces a mirror like finish. Many Model-A engine rebuilders have this level of machine capability however, likely there is more that do not. Just because it is a freshly machined head or block does not mean the surface finish is satisfactory. In the day, Ford used a segmented stone with coolant to finish the surface. This produced a finish even nicer than what dry-stoning a valve seat produces. A cut with HHS or Carbide cutters will never produce the proper RA finish.

Also, typically when Copper Coat must be used on a head gasket, it is band-aiding something. Prove me wrong on this.

[alexiskai]

Originally Posted by BRENT in 10-uh-C

Also, typically when Copper Coat must be used on a head gasket, it is band-aiding something. Prove me wrong on this.

You're not wrong but that perspective is not actionable. Almost every car has components that are not in ideal shape. Owners have to make careful decisions about which repairs should be done when and how. Knowing that, for example, a block has minor pitting and should ideally be surfaced does not commit me to having that done before I contemplate putting the car on the road. Sometimes a band-aid is the right treatment for the situation.

[BRENT in 10-uh-C]

Originally Posted by DJ S

Glad to hear you had good luck with your installations. I however did not and it was not the mechanics fault.

I followed the directions, no sealer. Re-surfaced block and head. After 5k mi, I ended up with a combustion gasses in the cooling system and red silicone in the radiator.

I think we can all agree the failure rate is quite high with this gasket (Snyders Part #A-6051-M) and it is prudent to advise against the use of it.

I guess I don't see it that way, ...and that's ok. Many over the years have used this gasket successfully without any trouble. If every one of these gaskets was a failure, they would have been removed from the market. Especially by the vendor you are referring to.

My take... If you were able to travel 5k miles, was it really the gasket's fault? I say No. Likely the cylinder head lost its clamping pressure to the block for some reason. Many ways this could happen. Thinking about this, ...lets assume this engine traveled an average of 30 mph for 4,500 miles before the failure ever began. That is somewhere around 150 hours of engine operation without a problem. Think about that, ...that is a long, long time. My vote it was something other than the head gasket caused the failure yet the gasket gets the blame.

[BRENT in 10-uh-C]

Originally Posted by alexiskai

You're not wrong but that perspective is not actionable. Almost every car has components that are not in ideal shape. Owners have to make careful decisions about which repairs should be done when and how. Knowing that, for example, a block has minor pitting and should ideally be surfaced does not commit me to having that done before I contemplate putting the car on the road. Sometimes a band-aid is the right treatment for the situation.

Colin, I don't disagree with you however maybe we could agree that when a component (-i.e.: Block deck or Cylinder Head deck) is not in ideal shape, criticizing a component that was not designed to function outside of that environment is kinda unfair. Suggesting that it has issues is much akin to spreading misinformation.

[JayJay]

Originally Posted by BRENT in 10-uh-C

Colin, I don't disagree with you however maybe we could agree that when a component (-i.e.: Block deck or Cylinder Head deck) is not in ideal shape, criticizing a component that was not designed to function outside of that environment is kinda unfair. Suggesting that it has issues is much akin to spreading misinformation.

I'm not sure that anyone is criticizing the gasket - just reporting that experience with it (at least among those chiming in here) has generally been less than favorable. Clearly in order for it to work properly requires a set of bounding conditions of surface finish, and I'm not sure that has always been considered (I certainly didn't when I tried it). Replacing a head gasket when the block and head have not been decked as you describe - seems like the graphite gasket has a wider margin for imprecision in the surfacing. Having an engine out and in the milling machine for a complete rebuild is a bit different situation than replacing a gasket that has leaked on an otherwise adequately running engine in the car. I think we'd all like to have the opportunity to build an engine from the ground up to full tolerances but that opportunity doesn't always present itself.

Brent, as usual, you've given this discussion a different and thoughtful slant. I'm getting ready to build up a Burtz engine and haven't looked at the finish of the block or head yet. I'll have to evaluate when I get to that point.

[alexiskai]

Originally Posted by BRENT in 10-uh-C

criticizing a component that was not designed to function outside of that environment is kinda unfair. Suggesting that it has issues is much akin to spreading misinformation.

I agree that this kind of nuance is important to share. I was recently in the position of defending the Nu-Wrench cam wrench on the grounds that it's only designed to work for stock upper plates, not plates adapted for V8 points.

[JayJay]

Originally Posted by alexiskai

I agree that this kind of nuance is important to share. I was recently in the position of defending the Nu-Wrench cam wrench on the grounds that it's only designed to work for stock upper plates, not plates adapted for V8 points.

That's interesting. I use it on a distributor with "modern" V-8 points and haven't noticed an issue. Why would it not work?

[alexiskai]

Originally Posted by JayJay

That's interesting. I use it on a distributor with "modern" V-8 points and haven't noticed an issue. Why would it not work?

It *can* work but it relies on the points being in a particular location relative to the cam, so that when the cam is at a certain angle to the distributor body, the point rubbing block is about to ride up the lobe and open the points. However, I’ve encountered a number of V8-adapted upper plates that shift the location of the points slightly, so the rubbing block meets the cam at a different point. This causes the points to open when the cam is at a different angle than what the Nu-Wrench has you set it to. So folks will notice that they set the timing with the wrench and the points will already be open - meaning the initial timing will be BTDC a few degrees. This has no effect on the stock engine but can cause problems if you’re using other mods such as centrifugal advance or a very HC head.

[SAJ]

In 2017 MikeK observed that 50/50 antifreeze will trash a silicone-sealed gasket. That makes sense to me. I have the Snyder silicone gasket under a 5.5 to 1 Snyder head in our Tudor for about 10000 miles. I have been expecting it to fail due to the many failures reported after I first installed it. However I don't need to use antifreeze in temperate Auckland and just install the anticorrosion package without the glycol (purchased from Repco). This may be why my gasket has not failed.
I have and will continue to use the Best Graphtite gasket in new engine builds, just to be safer and sure.
They are messy to remove though, compared with copper gaskets.
SAJ in NZ