MM ventured out below the "cheddar curtain" today, taking a rare day off with the intention of checking out the clearance between the valve edges of the over size valves and the edge of the 75mm bore cylinder.
Things checked out OK, there is a bit of "casting misalignment", what you would expect from a cast part. Checking was done on cylinders #1 and #4. It is a tight squeeze, 5 pounds of parts in 3 pounds of space, similar to late model 4 valve bike engines. Valve area is not as great as on a bike engine, but given the valve spacing and bore diameter limitations, the valve sizes being evaluated are "maxed out" for the combination. MM shot some inspection cam video, perhaps he will post it up to the diary.
The larger diameter valves give the benefit of allowing some valve throat and valve pocket machining and matching, correcting some fairly serious misalignment in that area of the cylinder head. The flow increases have been quite good for the amount of effort expended in these areas.
Some time was spent in the "Dungeon Laboratory" crunching some of the flow test data, and as soon as the test notes have been edited, I'll be posting a "Data Dump". I'm working on a more comprehensive simulation in EA Pro, once that is done, an additional "dump" is planned.
There was a side trip to the shop of the Mini Maven to return some borrowed bits from the "Grenade". Luncheon was at the local pub.
Fordboy