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MikeES

Head gaskets or lack thereof.

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MikeES
I have confirmed the rules with the local tractor pulling club, and we can run any type of head gasket (or non at all). To get more hp out of our M20 twin, I would like to put a thin copper head gasket (where to find one is a mystery) or no head gasket at all (more compression without modifying parts). After market parts are available for the single Kohlers but I have not found a source for the boxer twins. Years ago I read an aritcle by Permatex that showed a whole automotive engine put together with no gaskets just RTV silicone (of various colors). I have looked at the displays at the hardware/auto stores but I don't find something that could be used in place of a head gasket. I use the Permatex RED all the time for oil pans, breather covers, intakes, etc. Does anyone have any suggestions or experience in using hi-temp silicone as a head gasket in these air cooled flat head engines? Any other ideas and all ideas are welcome. Thanks. Good Luck! Mike S.

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JonetteP
Hi Mike, this is sort of reverse to your question. About 15 years ago I made a copper head gasket for my friends ski-doo olympic. The problem was that it had been overbored so much that the compression ratio was too high. So, we started with a 2" piece of round tubing. After cutting it legthwise, we proceded to flatten it. After about an hour, my friend and I had it flat. It was very thick copper, about 1/8 inch. My friend sold the sled to a youger guy, who was very cocky, and it ran fine. About 6 months ago a guy came up to me in a bar and started bs-ing. Turns out, he bought the sled, and it still runs! I think if you make a head gasket it will work fine. The only problem with copper is that it work hardens. After you strike it, the molecules become aligned. To work the head gasket, you must reapply heat. The heat will soften the copper. I would also recomend that you retorque the head bolts more often. Hope this helps. Neal Pierce Sales & Service serving you since 1950 call 507-534-2431

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HubbardRA
I also was into pulling. On my last tractor, a 14 Hp Kohler, I used a 10 Hp head with a smaller combustion chamber but same bolt pattern, then shaved .060 off of the head. This left .035 valve clearance with the gasket installed. This is the second engine that I have run this way with no problems. First was a 16 Hp Kohler. By the way, for those of you who may consider this for a work tractor, "Don't do it". These high compression heads cause overheating, and hot spots in the combustion chamber. It doesn't hurt for the short periods that the engine is run at tractor pulls, but will drastically reduce the life of a work tractor engine. Rod H.

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Dutch
Mike, I don't know anything about pulling, but Midwest Super Cub sells copper head gaskets for K series. Maybe they can supply twins also. > http://www.midwestsupercub.net/engine_parts.htm Here's a link to Permatex. > http://www.permatex.com/index.asp Any large roofing company should have copper sheets in various thicknesses. For the small pieces you need, they probably have free scraps. I like Pat's second set of heads suggestion............

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MikeES
Thanks everyone. Dutch, I did check with Midwest Super Cub, they don't carry gaskets for the twins. I will check into making or having someone make a set of thin copper gaskets. Rod, would a velocity stack help with this engine? Remember the inlet of the carb has a 90 degree elbow on it, so the stack would be attached to the ell. Note: In the Stock Altered class we have been fairly competitive with this tractor (917) with few 2nds and 3rds, and the engine is bone stock (still has original rings). We hope to humble a few Cubs next year in S.A., like we have done in the Stock class. Mike.

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thedaddycat
You can "soften" metal by a process called annealing. Heat to a bright incandescent heat and put it in a five gallon bucket of wood ashes, vermiculite, or perlite. Leave it to cool for a day or so. The slow cooling allows the cristaline lattice structure of the metal to "unpin" the edge dislocations that cause work hardening. With steel you can get it hot in the wood stove but I think copper might melt or deform if you had a good hot bed of coals and left it in too long. One trick blacksmiths use when heating or tempering smaller parts is to heat a large chunk of steel and use it to heat the part. That way you don't risk overheating which would take too much hardness out(if you were tempering a part), or burning up the part by direct exposure to the forge. Quenching hardens the metal, tempering is controlled reheating to take the brittleness out of it. An example would be a file, which is very hard but also brittle and untempered. If you take an old file, sand it clean and heat it with a torch you can see the oxidation colors run with the heat applied. A light straw color is slightly tempered while a blue or grey color if fully tempered(no hardness or brittleness left). Often parts are made from annealed stock which is soft and easy to work, then quenched to harden them and then tempered to "unbrittle" them. This is just a basic outline of the process, visit a blacksmithing site like keenjunk.com or anvilfire.com to find out a lot more.

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HubbardRA
Mike, I modified an air cleaner on a 12 Hp Kohler and machined my own velocity stack (more of a flow straightener) that would fit inside and replace the sharp bend with a smooth radius. It seemed to make some difference in engine response, but not enough that we could see a significant improvement in overall Hp gain. I also like to put about a .25 inch radius on the edge of the cylinder that faces the valves to improve flow into the cylinder. If you have a 3600 rpm limit like we had, sometimes you can gain usable power by going to a slightly smaller carburetor to keep the flow at a higher velocity as the engine becomes loaded. It can increase the torque. At one time, we were running a 10 Hp B/S. I found out that the same carb was used on engines up to 16 Hp. I changed to a carb and draft tube off of a 7.25 Hp engine. We saw a significant power improvement. In fact, we had no rpm limit at that time, so I re-set the governors so that I could leave the starting line at 6000 rpm. This was also a rev limiter because it was controlled by the governor. Rod H.

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JonetteP
Hi Mike, is porting allowed? If so, you can also gain some torgue there. Also, The legnth of your velocity stack is very important to provide the best torque, horsepower. It is very much like tuning the length of the exhaust on 2 cycle engines. I think it is possible to make a variable length intake port for your engine to allow a change in the engine rpm and fuel velocity. We ran into a problem with our 9020 when we ported the block, shaved the heads, and matched the intake and exhaust ports. We custom built stainless steel mufflers. Then had to add kohler mufflers to provide some back pressure. We had to then take off the mufflers because of too much back pressure. Now the engine surgess under load? We are going to try a stock intake manifold now to see the results. Hope this helps. Neal Pierce Sales & Service serving you since 1950 call 507-534-2431

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thedaddycat
One thing I learned from motorcycling, the gaskets between carb, manifold, and block are sometimes smaller than the casting. Fit the gasket up and trim the inside diameter to match, then sand down the rough edges of the gasket. This eliminates a flow restriction that some folks don't ever think about because it's not part of the metal that is being smoothed out during porting. I have used a long flexible spring with emery colth taped to it and snaked it through the intake manifold while it was chucked up in a drill to polish the inside of the manifold.

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HubbardRA
Neal, From your description of needing backpressure, and having a surging problem, it sounds like your air-fuel mixture does not match your new configuration. Ran into this many times when pulling with motorcycle engines.

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