I do a "street port" on the B23 heads, that profiles the intake port a bit, and smooths the transition across the valve seats. I do no work on the exhaust port. I also back cut the intake valves.
As mentioned by another, this is not required unless one uses more compression and a big cam. The Canadian B23E is a perfect candidate, and I have not worked on any others.
The pushrod motors can use all the help they can get.
Rhys

I think it would be a waste of time unless additional work is done requiring more flow. A big cam, or using the head for a Turbo application would see a benefit.

Upgrades to the exhaust system (larger diameter Turbo rear pipes) and this port work might gain a small benefit but the biggest part of the puzzle is getting rid of the low-lift short-duration stock M cam.
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::: Rob Bareiss, New London CT ::: 92 244 ::: 90 745GL ::: 90 745T ::: 84 242DL ::: 90 745T Parts ::: Used to have : 86 244DL, 87 244DL, 91 244, 88 244GL, 88 744GLE, 82 245T, 86 244DL, 87 244DL, 88 245DL, 89 244DL!