I'm not planning on doing it, I don't even own one, it's just curiosity. I've seen A4's in some pretty big boats and it won't swing much of a prop so I figured a torque increase could be useful in many cases. Overheating was a problem with Ford flatheads because the exhaust ports went through the water jacket - I don't know if that's the case in an A4. A bigger prop would be the nautical equivalent of a set of gears, so yeah - a set of 4:11's
I fully understand about the durability value of an engine being lightly stressed. That is why I stated several times that I'm talking about MODERATE modifications - things like line honing the mains, balancing the rotating assembly, improving oil drainback and so forth actually increase
durability while they enhance performance. Pretty well everything I mentioned would add little or no cost to a normal "bolt it together" rebuild as well - it's mostly just craftsmanship.
I'm not talking here about throwing a blower or dual 4's on it, just a careful and precise build with a few bits of performance enhancing technology.
For those who think it is already optimized, think of the original Chevy small block - wonderful engine, IMHO the overall best engine of any kind ever made BUT it was extremely easy to improve everything about them simply by improving them from a mass production build standard to a precise "machinist" standard - with no decrease and usually an increase in durability.
Keep those responses coming in.