I've been describing my 413-440 swap in another thread
, mixing and matching parts so I don't have to replace the exhaust system and rad. But there's one complexity that hasn't been talked about, and I knew nothing about until now. The 413 uses an internally balanced crankshaft, so that means the harmonic balancer and torque converter are neutral weighted. But a 440 can be either internally or externally balanced, depending on whether it has a forged or cast crank. If it has a cast crank, it needs external weights on the harmonic balancer and torque convertor. Unfortunately, the 440 I put in has a cast crank, and the original torque convertor in my motorhome is neutral weighted. That means I have to pull the engine again and either replace the TC with the proper one, or get a balancing flex plate like this one
. So much stuff I've never heard of, and finding out the hard way. I found out about this by a high RPM vibration that I put down to old motor mounts, until I decided to look into it further.
So anyone making a 413 to 440 swap has to remember that all 413 engines are internally balanced, but a 440 can go either way