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Swapping my olds 455 today, finding that the PTO that was on the flywheel of the old motor, doesn't fit the flexplate on the new motor. The flexplate is half the thickness or so at the bolt holes so the PTO doesn't mate up to it flush. Am I missing the obvious or is there another part when using a flexplate instead of flywheel? Thanks

john
 

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The flexplate pto is counterbored on the engine side to register over the crank, the solid flywheel pto has a step to register inside the flywheel center hole. What he said above, elaborated on. Also Chev and Olds are not the same if changing one to the other.
 

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It doesn't fit because the flex is thinner than the flywheel, correct? I went from a flywheel to a flexplate and i had to make a 3/8 thick spacer for between the flexplate and pto.
 

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That would be true yes. A spacer or repositioning the engine back slightly would accomplish the same driveline position you had with the solid flywheel in relation to the pump shaft. Make sure the spacer registers over the end of crank to center it (needs a counterbore), don't rely on bolts to center it. Also make sure bolts are grade 8 equivalent. Most allens are (steel).
 
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