Originally Posted by Kai
Well, yeah, I can understand using one on that oddball head, but how often do you see those?
For the others with the standard 81mm combustion chamber, it just seems like something super-obsessive. What's the average displacement of a B-series combustion chamber (say, a PR3,) anyway?
Well if you overbore the cylinders, you'd go with an overbored headgasket to match. It's not the change in displacement that matters, its the fact that you are going to have material all the way around the circumference of the cylinder disrupting flow as it enters the cylinders from the head, and as the pistons compress it, and as it exits the head. The edge of the gasket in the cylinder will cause a turbulent flow inside the cylinder.
Also, it's a common practice for people who go with an overbore to have the combustion chambers bored to match as well.
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