Bottoms Up!

At the bottom end of a Miata engine, under the oil pan… you will find the Main Bearing Support Plate (MBSP). The function of this item is to stabilize the main bearing caps, and to throw a wrench in the spokes of your smooth dis-assembly project. Mazda decided to use a 10mm external Torx fastener here… just to make sure you are willing to spend the nine dollars on a Torx E-10 socket. I see no other reason for this specification of fastener. It serves a good purpose in that it prevents the casual wrench turner from going much farther into the engine… although I struggle to see why you would have the oil pan removed if you were such a person. Perhaps they figured I would shake my fist at the sky and scream “curse you Torx bolt”… and then promptly button the engine back up and head to the Mazda dealership. I don’t back down from a challenge, so I went to Sears.

Once you have all eight of the Torx fasteners free… you can simply pull the plate free!

Just kidding! I should not be so misleading. The plate is practically glued on to the engine by the sealer, and you can pull all day but it is not going to budge. You will need some form of gasket removal tool to do this properly. Do NOT under any circumstances attempt to pry at it with a screwdriver. This is a basic concept of working with mating surfaces. If there is a gasket… or sealer… do not scratch the mating surface!

Once you have the plate cut free… it should pull right off (for real this time).

Take this moment to stare in awe at the inside of your engine. Seriously… do it. Mazda built a fantastic little engine here, and you are going to want to know how everything goes back together. Take pictures. Pay attention to the orientation of the connecting rods. They only go back in one way. Mazda put some stampings on the exhaust facing side of the rods where the cap split is. They must go back in this direction… and they must go back in the same bores, with the same pistons and wrist pins (assuming you will reuse them). As far as the main caps are concerned… Mazda was especially kind and stamped them with their order number from front to back on the engine. Once you are done staring, and assuming you will not be removing the crank/pistons/rods immediately… you should promptly cover your engine with a large garbage bag.

Tomorrow I intend to remove the rods and pistons… and then pull the crank out of there. Here are some pictures of last nights fun.


~ by ddmotorsports on March 23, 2012.

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