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I agree with that. 4032 is great for street motors and just about any all motor build. The tighter clearances should pay off with better longevity of the piston itself and the rings (they're less exposed). The Mahle pistons are 4032, have coated skirts, and generally one of the best off the shelf 4032 piston makers out there. That's what I would use if I was going to start a new build today.2618 expands more, which generally allows them to take more of a beating, so you have to adjust your clearances accordingly. 4032 has more silicone content which allows you to run tighter clearances since the material expands less than 2618, however, at the expense of being more brittle. I've seen a 4032 piston shatter in a high hp turbo car before. Generally I'd say that 4032 is more suited for all motor applications...2618 is more suited for the abuses of a turbo car. I wonder if anybody runs a 4032 piston for methanol FI setups.
On 94 octane, you could easily run 12.5:1 reliably...just make sure your tuner knows and understands what they're doing.
As for coatings, moly skirts are nice...theoretically...wiseco shelf pistons come with these already. If you're going to coat the piston top, you should coat the chambers as well. Heat will be absorbed through the path of least resistance. Keep it off the piston tops and the head get's to absorb more. Personally, i've never seen any measurable differences. I can see how it could be beneficial, but chances are, if you're at the point where you're counting on coatings to make a difference in the overall picture, you wouldn't be asking.
You can safely go to 88mm on stock sleeves...maybe more...
2618 can take more abuse b/c it has a higher tensile strength. That means when high HP starts pounding the piston, high revs start to stretch the piston, and high heat starts to soften the piston, 2618 has a greater ability to take the load without falling apart in a catastrophic manner. The downside is that the coefficient of thermal expansion is greater meaning you have less consistent skirt profile as temperature varies. This makes it a little bit more tricky to get daily drivable longevity out of a 2618 piston versus a 4032 piston.