From The Sermons of Bob Hoover, VW enthusiast
Under a bench in my shop I got a box of gaskets. Some are real gaskets, others are a piece of paper on which a gasket lay while being sprayed, leaving the outline of the gasket. Others are drawings of gaskets. One is a carefully made STEEL copy of a gasket for a magneto mount I once manufactured.
Tucked here and there around the shop are rolls of gasket paper and cork; some neoprene sheet. Odds & ends of poster-board, even a few shirt-cards. (Back when, the laundry folded your starched shirts onto this nifty white card.) Also some breakfast cereal boxes. A hunk from the side of a carton that carried laundry soap. Some leather. Lotsa stuff, all good for gaskets.
It wasn't too many years ago that a mechanic was expected to make his own gaskets. You'd take the part, make a pattern, check the fit then go make a gasket. Simple things, like an oil pump cover, you just draw around the part; cut it out. In the case of thirty-year old Volkswagens, those days may come again. Fortunately, veedubs only use a few gaskets; easy ones to make; like cutting out paper dollies.
The gasket basket provides the patterns, the other stuff is material useful for making gaskets. To make a gasket you simply trace its outline then cut it out; scissors or razor works fine. You can use a razor to make the holes but a hole-punch works best. Just press the punch firmly against the material and give it a smooth twist. Thicker stuff, tap the hole-punch with a plastic-headed mallet. (You can get hole punches in an incredible assortment of sizes; see the Harbor Freight catalog, or the one from Enco Equipment Supply; machinists make gaskets too.) Work on a piece of wood. (Yeah, I know the dining room table is wood, but...)
The typical gasket, as for your carb or sump, look like stiff paper, because that's what it is. But it's not ordinary paper. Gasket material is made with resins designed to resist oil and gasoline. Without the resins, a paper gasket is nothing more than a slow leak. (A lot of VW sump gaskets are like that.)
When you make a gasket from paper or cardboard you must treat it with sealant. A treated cardboard gasket works fine for the sump but a hard-paper gasket for the carb tends to ooze no matter what sealant you use. To prevent this, buy a roll of resin- impregnated gasket material of the proper thickness. Good auto- parts places carry a wide variety of gasket material whereas the chain-store type of parts store many not even know what you're talking about.
Commercially-made gaskets are usually better than anything you make yourself. They're accurately cut and use the right material (except in the case of those sump gaskets I mentioned earlier). And commercially-made gaskets are usually inexpensive -- certainly less trouble than making your own. When you buy a gasket, smile at the man and ask for two. (Go on; he'll think you've got a whole shop full of engines back at the house.) When you get home, write down what the gasket is for and the date, right there on the gasket itself. Then put it in your gasket basket. Or gasket book. Or hang it up someplace out of the way (maybe over there with that collection of fan belts). Because the next time you need that particular gasket the kid behind the parts counter is liable to frown and say "Did you say an AIR COOLED Volkswagen?"
They sell some great gasket sealants nowadays; as tough as RTV but in a spray-can. Marvelous stuff. Makes your bug forget how to drip.
Historically, gaskets were sealed with just about anything that came to hand, like tallow. Or beeswax. A lot of steam engines called for SOAPED gaskets. (I don't know what kind of soap they used but the gasket surface was often corroded by the time I got to see it.) The usual stuff was heavy grease. Or soaking the gasket in oil. Some called for painting the gasket with... ta da! Gasket Shellac! (I'll bet you've wondered why they called it that.) Gasket shellac was just that; a thick, gooey shellac. And like all shellacs, the vehicle (ie, the stuff that made it fluid) was alcohol. Gasket shellac was the stuff that resisted gasoline; you used it on gaskets and washers that came into contact with gas.
Peeling a page from the shellac idea, I've made successful gaskets using urethane varnish as a sealant. (No, I won't tell you where I used them. But they worked.) Different paints might do the job for you. Or even water. (We usta soak cork gaskets in water before torquing them down. It seemed to keep them from tearing. You'd come along later, re-torque them.)
What's a Gasket?
A gasket's job is to make a leak-free joint between two surfaces. Unless the parts are polished like a mirror, their surfaces have tool marks that form channels large enough to pass molecules of oil, gas, water, air, steam... whatever the gasket is trying to keep in. The gasket is compressed into those microscopic grooves and seals them.
In theory, the best gasket is none at all; parts so slick they stick together like Jo blocks. Nowadays, what with numerically controlled tools and other innovations, we are blessed with machined surfaces so finely finished that paper gaskets may not be necessary, a coating of sealant is enough to provide a leak- free joint. But as a general rule, if the joint was fitted with a gasket, use a new gasket on reassembly.
I don't know who showed me how to make gaskets, probably my grandfather; maybe my dad. Us kids would be standing around, watching somebody work on something and they would hand us a part and say 'Go make me a gasket for this. Use the red stuff,' and we'd take the part and go make a gasket. A child's chore; something given to the youngest apprentice. Like cleaning parts. (Yuk!)
Coming home from Baja, Jaysie and I were 'way the hellangone south of the line, out on that long empty stretch between Ciudad Insurgentes and Huatamote, and there's this big Ford camper, blowing steam. Older couple. Oregon plates. BIG camper.
In Baja you stop to help and there was already some folks there but their English was worse than my Spanish and the feller in the camper didn't know if they were trying to steal his engine or fix it. Thing was, he'd blown a gasket on his water pump. (He had some other problems, but the pump is what slowed him down.) So we made him a gasket. Used a Wheaties box. Sprayed it up good with Rustoleum paint. The feller's eyes were the size of golf balls, watching me and Mr. Avilos fix his truck, as if gaskets only came from the Great Parts-House in the Sky.
When did folks stop learning useful things?
A week or so ago we were discussing my recent success at making gaskets. You mentioned that it was easy to make gaskets if you the proper material for the job. I guess you mean there are different types of material for different parts of the engine. Care to elaborate?
Gasket material comes in different thicknesses, a distinction obvious by inspection. You'll recall that your oil pump uses an extremely thin gasket whereas your exhaust flanges use ones of metal, wrapped around asbestos (yes, you can still get asbestos gasket material... if in a kit manufactured in a foreign country).
The object of the thin material is to permit the pump to properly align in the bore of the crankcase, a thicker gasket would cause some misalignment and reduce the oil flow. On the cover, you want the minimum possible clearance between the ends of the pump's gears and the cover plate, hence the need for a thin gasket.
Most gaskets are meant to seal the joint between two parts for the life of the assembly. The best material for gaskets of that type is a kind of glue that hardens when exposed to pressure and heat. The gasket not only seals the joint, it bonds to both surfaces and must be scraped away when the assembly is dismantled for overhaul. Gasket scrapers are standard tools in any mechanic's kit.
Often times the joint in an assembly must retain oil yet allow for some degree of motion, induced either mechanically or by metals having different thermal coefficients, as in the case of the Volkswagen crankcase and cylinders. Such gaskets fall into the group of 'elastomeric' seals, as do shaft and tranny seals. Another gasket type is one intended to permit the parts to be dismantled frequenty, as is the case with your valve cover gaskets. For that task you want a material that will compress to form a seal but will not harden nor bond to the surface that must remain free. The usual procedure is to glue valve cover gaskets to the valve covers and leave the other surface free to form a seal with the cylinder head.
Your axle boots are another form of gasket, as are the boots on your tie-rod ends, although when the gasket is a molded elastomer, such as neoprene or silicone, we tend to call them 'seals' rather than gaskets, but as you can see the primary fuction -- keeping something in while keeping something out -- grease and dirt in this case, gasoline and air in others, is the primary role of gaskets. And seals.
The gasket used under your carb should be made of a material that will compress but will not bond. But once compressed the stuff tends to stay that way, meaning you need a new gasket each time you dismount your carb.
Some gasket material is permiable, allowing oil to pass through it. The cheap cardboard gaskets for the sump, as found in oil change kits, are like that. Such gaskets have a place, but not in a Volkswagen engine. The only reason they are there is because they are cheap and everyone expects a VW to drip. It doesn't have to be like that, as I pointed out in one of my sermons.
In theory, it's possible to machine surfaces to such a fine finish that they need no gasket at all. The VW comes close to that goal with its engine case but still requires a coat of sealant along the joint to keep the oil in and the dirt out.
Your window seals are gaskets of a sort, as is the seal around the windscreen or the bas of your radio's antenna. Gaskets (or seals) exposed to ultraviolet light must be made of material that will withstand UV degredation. And so it goes. Different tasks call for different gaskets, some thick, some thing, some soft, some hard, some flame resistant and so on.
Just as there's no on sealant that can do every job, neither is there such a thing as a universal gasket material, although paper, in all its forms, comes close. (Leather was once the most common gasket stuff, and is still used in a surprisingly wide variety of applications; some leather seals flew to the moon. Oil impregnated wood is still used for many shaft-sealing applications. Indeed, it's hard to find a material that hasn't been pressed into service as a gasket or seal. I once patched the hull of a dory with pieces of cotton fabric and varnish. The cotton fabric came from a ladies skirt. (Okay, it wasn't exactly a gasket but definitely a seal.)