413 to 440 swap - important detail

[rattlenbang]

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.

[DaveVA78Chieftain]

Almost all 440-3's are externally balanced.  The car version is where the forged crank was used.

[Wantawinnie]

Can't you just drop the transmission instead of pulling the engine?

[rattlenbang]

Actually, after TONS of research, I stumbled on a google books table that gave the location, size and weight of the torque converter weights. Gonna make 'em up and tack weld 'em on through the inspection opening in the bottom of the tranny. What a relief!

[Froggy1936]

Fantastic just a note : Welding will have to be electric (to keep from excessive heat to convertor and rear main seal. make sure they are thin enough not to hit rear of engine block . and welded well enough to stay in place . A piece of steel launching @ 5000 rpm will travel all the way through the roof of the camper  Unless stopped by a human in the way ! Frank

[rattlenbang]

Yup. The dimensions are 0.15" thick, so that should fit no problem. The stock ones are spot welded on, as they are only 20oz each. Shouldn't take much to hold them in place. I got a mig welder that I'll take to it, and suspect that I'll have to grind off a bit to compensate for the material I'll be adding. I wonder just how exact is has to be anyway. The plans I have show dimensions to 3 decimal places, and I can't believe they have to be that exact. it's the mass that's important anyhow, and that's a simple 2 weights at 50 grams each, no decimals.
You can buy them on ebay -two tiny bits of metal - for $50 bucks plus shipping  :)rotflmao