I need to install a connection in the cast iron stack to accommodate a 2" washer drain. I was thinking about supporting the stack, cutting a section out and installing a 4" pvc wye to run my drain pipe to, which is about 14' away.

Sure it will work, with a min 1" slope per 4'.
But code where you are might limit the distance from stand pipe to stack (3'?), plus whether you can put PVC under a vertical run of cast iron. But people do it anyway.

Hi Dmcclain52

As Joypulv pointed out you can't insert a PVC wye fitting into the middle of a vertical cast iron stack. As mentioned, people do it (using shielded clamps), but not plumbers... ;)

Here, you would be much better off supporting the cast iron stack using RISER CLAMPS (see image) and then cut in a cast iron no-hub wye fitting (only available at a local plumbing supply store)... use shielded clamps to secure a water/gas-tight installation (see image).

After you get the cast iron fitting installed you'll need to transition from cast iron to PVC. This can be done using the cast iron wye if you get a wye with a tapped (threaded) branch on the wye fitting, or you could also accomplish this using a shielded cast iron x pvc transition clamp...

After that, you will also need to consider how it is that you plan to VENT the washing machine drain... ABSOLUTELY required to keep sewer gasses from escaping into your home, OK?

Care to discuss all this more just let us know.

Mark