Wood – How to cut an angled cut with low clearance

repairtoolswood

I need to cut a header down on an angle to match my stairs. It needs to be cut on a 51° angle, which my circular saw can handle, but there isn't enough clearance under the joists to get my saw in there.
header from the front
header from the end

What kind of tool should I use to cut this? I have marked lines on the front and back, and I'm considering using a reciprocating saw and just trying to hold it steady. Is there a better way?

Easiest would have been to cut it before placing, but I really had to whack that thing to get it in and regardless it's in place now.

Update:

I just used a hand plane and started going to town. It worked surprisingly well.
planed header

Best Answer

If you can get a rough cut with a Recopicating saw, you can use a handheld power planer to finish the cut and get the right angle. Just attach a scrap piece, cut at the correct angle, to the planer fence.