M engine swap

41106 · Sep 27, 2009

Planning to replace my current wore out M engine with a 400/450 engine. Figure now's the time since I need to rebuild one anyway. My question is what all do I need to change to make it work as far as flywheel, clutch, etc... Any heads up you guys can offer me would be great.

rustred · Sep 27, 2009

should be pretty basic as both engines are basicaly the same. 400 would have larger diameter clutch, and i think the splines are diff.

D Slater · Sep 27, 2009

Unless you have a late M with a 12 inch clutch or a late belley pump housing to clear the 12 inch clutch. Use the M flywheel and clutch. If you could use the 400 size flywheel and clutch the clutch plate needs changed to a SM type.
Switch throttle arm and shaft on governor. Run vent line in top of valve cover to air cleaner intake pipe vent line opening. Depending on what model M it is and if a live hydraulic pump is used or not a ignition drive housing and shaft from a SM or late M may be needed to match the 400 front cover bolt pattern. If using a 400 carburetor the choke lever will be toward engine instead of out like a M. So choke rod will need a little work. Sometimes the 2 head studs where the M throttle bracket mounts are not long enough on a 400,450 to have full threads on the nut after bracket is added. Stock ignition unit for a M may have to much advance for a 400,450.

M engine swap

41106

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rustred

Well-known Member

D Slater

Well-known Member

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