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grinding a crank


Chris727

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Has anyone here ground a crank more than ten thousandths undersized on the old cast iron briggs? I was thinking of going to 20 thousandths undersized. Thanks. Chris
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Hi, I am away from my data, but as I remember Briggs only makes .020 under rods and Kohler only makes .010 under. I may be wrong, but I believe this is correct. I am not sure, but as I remember I have a 7 hp en;gine with the crank ground, and I couldn't get an undersize rod for it several years ago. If this happens the only alternative is to have the ends of the rod and cap milled off and then have it rebored and finish honed. Al Eden
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Where there's a will, there's a way. If parts are unavailable but your connecting rod is still intact, you can have the crankshaft welded and turned to an oversize. Then have the original rod machined accordingly. Talked to someone a while back who was rebuilding an engine for which parts were obsolete. He did a lot of research and rebuilt his engine. On his particular engine, pistons from a Ford 302 were .025 over the standard bore, the piston pin was .005 over the standard, but the piston matched up otherwise. He had the cylinder bored .025 over and the wrist pin bore of the rod bored out and bushed to accept the pin. As far as the connecting rod, he found inserts (the type in automobile engines)that were very close. He had the crank turned and the rod machined to accept the inserts. Been working great for at least three years now.
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What Pat is talking about, and Al, used to be the way that the older engines were rebuilt. If the bore was still round but worn, we used to hone and then knurl the piston skirt to enlarge it so the piston would not be sloppy in the bore. There are lots of ways to save an obsolete engine when parts become a problem.
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