Modified Model 72 Maytag Data Wanted

[Francis]

Several years ago, I saw a Maytag Model 72 with vertical exhaust pipes. At that time I asked the owner how the modification was accompished? I was told that the cylinders were just rotated 180 degrees. Since I wasn't too familiar with Maytags at that time, I was under the impression this was a simple modication. After acquiring, disassembling, and assembling a Model 72 I became more knowledgeable about the construction of the engine. Subsequently, I started to think about modifying it so the exhaust would be pointing upward instead of downward. Of course if the cylinders are rotated, then the pistons also have to be rotated to line up with cylinder ports. When the cylinders are rotated, they no longer match the intake ports on the crankcase.
My questions are - has any one made this type of modification? If so, how did you make the cylinder intake ports match the ports on the crankcase - were the crankcase matching ports ground out with a die grinder? Did the old crankcase ports have to be blocked?

Francis

[Andrew Mackey]

You can modify the block with a die grinder, to meet the requirements of the inverted cylender. As long as the inverted cylender mounting flange covers and seals the original port opening on the block, there should be no problems. Crankcase intake from the carb is timed thru a port in the crankcase, and the crankshaft - that is why the model 72 cannot be run in reverse. I did see one 72 run backwards - the intake system was bypassed with a lawnmower carb, and a reed plate mount was brazed onto the block. Run off battery and coil, this engine would run in either direction On the regular 72, transfer and exhaust timing is made by the relief decking on the pistons. The exhaust deck is closer to the wrist pin height than the transfer port, and that is what makes the engine exhaust first, before opening the transfer port. If you invert the cylenders, then you must also invert the pistons, otherwise, all the engine will do is back flame the ignition into the block A very UNdesireable situation indeed

If you die gring the block, I suggest a total engine tear-down. Die grind the block, one cylender at a time. Die grind the flange and internal block obstructions carefully, only removing enough material to meet the opening on the cylender. You can check your progress by installing the cylender on the block, and looking thru the other cylender mounting space, see directly thru the block, and see the port mating surfaces. With a new gasket, and the cylender just snug, you should see no daylight at the flange mating areas. If the old port should overlap the inverted cylender flange (you see light thru the opening), then the old port area must be built up, either by brazing or welding the old port closed, and machining the flange deck flat. Mark the flange and cylender, so they can be matched during re-assembly. Also, heep the pistons matched with their respective cylenders, so you will not loose ring seal. When die grinding, make sure to thoroughly rinse the block and the cylenders with Kerosene, in order to remove any foreign materials. Any die grinding residue left within the engine internals, will quickly make scrap out of the engine.
Andrew