I know it's been discussed many times, and I remember even posting in various threads and linking to valve info, but I can't find half of the threads now, including the one I was really looking for. So, I figured I'd start a thread with an easily searched name that we can conglomerate all the info in.

First, what's being used for the largest valve sizes? How large can we go before it becomes counter-productive/unfeasible? I remember linking to some Nissan L28 valves and Toyota 3TC valves, 3TC having the largest options. Of course, custom valves are usually available in any size you want if you want to pay, but sometimes it's nice to have off-shelf options. Also, what size seats to use with these?

2nd, and this is what I remember discussing before but can't find, does upgrading the intake as large as possible and leaving the exhaust stock or at +1mm give an advantage? Or vice versa? Does boosted vs NA build factor into this decision at all?

Lastly, anything else to do with oversize valve choice lol. Those are the 2 main questions I had in my head, but I'm sure there's more. Does casting type (IE swirl vs bathtub) make a difference? How much do oversizes increase compression/change chamber volume? Etc etc...