Ok, my wife was out of town and I had time, so I ported my older 266 last night. It had the SE Mahle cylinder on it, labeled 50ZN11. I had an extra XP cylinder (50ZN13), so I decided to do that one.
Without base gasket, the numbers for the XP cylinder were:
Exhaust: 106
Uppers: 122
Intake: 70
Squish: .017"
I took down the ridges on the lower transfers and smoothed them out, being careful not to go deep towards the case. I removed some material inside the transfers behind the "bridge" to skinny them up as well.
Raised exhaust roof slightly to 102, really widened it up and funnelled it outwards. Exhaust roof was pretty flat from the factory, so I followed the factory contour. Polished everything up very nicely afterwards with aluminum oxide stone, then emery paper in a mandrel, then polishing compound and a felt wheel. Port matched muffler and gasket. Muffler was already modded.
Lowered intake to 78, widened, and cleaned up. Left it rough.
Went over edges with diamond ball, and then ball honed both directions.
Advanced timing 0.025" off the key.
Now it's sitting at:
Exhaust: 102
Uppers: 122
Intake: 78
Squish: .017"
I heat cycled it a couple of times, and then put it in the wood this morning. Pulled a 25" full comp with low rakers in some 20" green pine with way more power than before. Throttle response is way better. Tunes at WOT @13.2k. Holds 9.5k in the cut. Sounds great.
I'm happy. I used the full-circle piston that was in it, but I think I will tear it down and replace it with the windowed Meteor piston sometime in the near future. I'll share some pics then.
I think I will use this recipe for the 266 build that I am working on in the other thread.