Hi folks.. I finally had a chance to resume this work... and here's the conclusion:
I did some measuring and the o'ring groove does have an uneven depth! Thinking the front of the engine as North, driver side as West, the 'Northwest' side of the o'ring groove is 0.031'' deep (good!), whereas at its 'Southeast' side depth is shallow as 0.025''. It seems like the block was not perfectly leveled when the o'ring groove was cut. Anyway, that makes the o'ring to protrude as much as 0.020'' in the 'Southeast' and 'South' (bordering with cylinder # 3) sides. I was concerned that the excessive protrusion would create problems sealing the cylinder #3 where the o'ring of cylinders #1 and #3 are adjacent. So I took the approach to 'level out' the protrusion of the copper o'ring of cylinder #1 by carefully block sanding it. I'll post final results when the time comes.
I'd have taken a much different approach to start with if I knew the copper o'rings would bring so much trouble. This engine doesn't need the copper gasket and o'ringed block to start with. It's a naturally aspirated alky engine with lousy 12.5:1 compression ratio. If I knew the copper o'rings were super glued to the o'ring grooves, I'd have had the deck machined, cleaned up the minimum necessary just to cut the copper o'rings flat. Then I'd probably use steel multi-layer gasket. A lot less hassle than the copper gasket, for this application.
I know the o'rings can be beneficial/necessity for highly boosted engines. I've seen high-end 250 race engines (4 figure HP) with three stainless steel o'rings per cylinder, two in the head, and one in the block positioned in the middle of the head's o'rings. We don't find machinists with such capability in every corner.
By the way... discussing the risk of potential coolant leaks with the copper gasket... a friend suggested considering the use of those 'coolant stop leaks', like those from Prestone or Bar's Leaks. I'm tempted to try it if I find a leak. Any comment?
Thanks for all the great input.
