Gaskets

[j4c11]

I am going to purchase a sheet of neoprene rubber for gaskets from McMaster for a non-cub application, but I got to thinking, why isn't rubber used more for gaskets? Seems like a neoprene rear end gasket for example could be used over and over again rather than having to buy a new every time. Is there a technical reason for not using rubber or is it simply a matter of material cost?

[J-Mech]

Rubber is used for lots of gaskets. The company Fel-Pro makes all types of "rubber" gaskets. Their Perma-dry Plus line is all basically rubber. Why doesn't CCC offer more rubber gaskets...... cost.

I like your idea.... but I'm really interested in how you plan to cut it and add holes in an effective manner. Rubber is hard to work with without a die to stamp it because it stretches so much when you try and cut it with a knife. I've not tried any of those sheets, though so it may be easier than I think. I'm also interested which product your chose, as McMaster sells more than one neoprene rubber gasket material.

Not to derail, just as a side note: I think most guys get all too hung up on the rear cover gasket. Silicone alone holds just fine. I don't have any issues with any gaskets on the cubs leaking once they have been fixed. I honestly don't understand why so many people change out a gasket just to have it still leak.

Please keep us up on how this works out!

[j4c11]

I bought the reinforced neoprene sheet (8525T55) for extra strength, and I think the nylon mesh may reduce/limit the stretching. I definitely can't cut the rear gasket by hand, you're right the holes would be hard to do. But I'm going to do the valve cover gasket for the K321 with an exacto knife and see how it works out .

[J-Mech]

I just thought of something else I didn't mention. Most all of the rubber gaskets that are made for applications have some properties that make them work best.

Lets use a valve cover gasket on a GM 3100 V6 engine.
The gasket on this application is all rubber. It fits into a groove machined in the valve cover so that when the cover is tightened down, the rubber cannot "squeeze" out the side. The groove makes the rubber hold it's shape, and therefore, do it's job. On the same engine, the intake manifold gasket (I'm using a Fel-Pro Permadry Plus for this example) is attached to an aluminum backing plate. There is rubber attached to both sides, and is not all that thick. When the intake is torqued down (not a very high torque) the aluminum plate again, hold the rubber in place. The fact that is glued to the aluminum makes it retain it's shape and not just "squeeze" out of place. There are countless other gaskets on lots of different applications that are made with this metal center plate.

I guess my point here is that a single piece of rubber used as a gasket for the rear cover, I fear, will just displace and squeeze out when you go to torque it. I think you will find that you won't be able to get the bolts tight enough without the gasket moving out of place. A paper gasket (such as the OEM one) will withstand the torque process and not displace when it is tightened as that material's "crush" strength allows it to retain it's shape. I'm not sure it will work at all...... but it may surprise me!

[J-Mech]

Originally Posted by j4c11

I bought the reinforced neoprene sheet (8525T55) for extra strength, and I think the nylon mesh may reduce/limit the stretching. I definitely can't cut the rear gasket by hand, you're right the holes would be hard to do. But I'm going to do the valve cover gasket for the K321 with an exacto knife and see how it works out .

That gasket is not rated for oil. Only detergents.

The Viton material would be a better choice, as it's an oil resistant material. Lots of oil seals are made of Viton.

[j4c11]

Originally Posted by J-Mech

That gasket is not rated for oil. Only detergents.

The Viton material would be a better choice, as it's an oil resistant material. Lots of oil seals are made of Viton.

I agree, but it's 4x the price, $31.89 vs $7.89, so I skipped right over it

[J-Mech]

Originally Posted by j4c11

I agree, but it's 4x the price, $31.89 vs $7.89, so I skipped right over it

That's why the OEM gasket is probably the best choice, and why they don't offer one made of rubber...... because of the price. I don't think the one you chose will stand up very long to oil. More than likely it will swell and leak in a short time period. I'll just keep siliconing my rear covers, and using the paper valve cover gaskets. Cheaper.

I'm sure that's not what you wanted to hear..... sorry.

[sbauerz28]

Originally Posted by J-Mech

I just thought of something else I didn't mention. Most all of the rubber gaskets that are made for applications have some properties that make them work best.

Lets use a valve cover gasket on a GM 3100 V6 engine.
The gasket on this application is all rubber. It fits into a groove machined in the valve cover so that when the cover is tightened down, the rubber cannot "squeeze" out the side. The groove makes the rubber hold it's shape, and therefore, do it's job. On the same engine, the intake manifold gasket (I'm using a Fel-Pro Permadry Plus for this example) is attached to an aluminum backing plate. There is rubber attached to both sides, and is not all that thick. When the intake is torqued down (not a very high torque) the aluminum plate again, hold the rubber in place. The fact that is glued to the aluminum makes it retain it's shape and not just "squeeze" out of place. There are countless other gaskets on lots of different applications that are made with this metal center plate.

I guess my point here is that a single piece of rubber used as a gasket for the rear cover, I fear, will just displace and squeeze out when you go to torque it. I think you will find that you won't be able to get the bolts tight enough without the gasket moving out of place. A paper gasket (such as the OEM one) will withstand the torque process and not displace when it is tightened as that material's "crush" strength allows it to retain it's shape. I'm not sure it will work at all...... but it may surprise me!

I've done so many head gaskets and intake gaskets on those and the 3400 engines I think I could do it with my eyes closed.

They sure have come along way with gaskets in general, but for the purpose of a Cub rear cover I bet a can of "Right Stuff" would seal better than any gasket.

[Shrewcub]

I am curious to how this works out too.

In my experience on rear end covers using RTV, is that once it fully cures, you could probably take the bolts out and it would never leak. On Cubs you still need the bottom ones for the drawbar tho.

[Calvins66Cub]

I just made some gaskets from this McMaster # 9470K37
Is was pretty easy to work with, and no leaks.
I did use some silicone also.