Hard to say. I think the big thing with setting a valve "cold" is for the engine not to be recently run - beyond this, the actual temp is probably not a big factor.
Whether you could let this valve ride is up to you. Nothing bad usually happens when you let one that is slightly out of spec go till the next adjustment. But I don't think you can assume it will be in spec if your garage was 15-deg warmer.
Personally, I wouldn't make extra work for yourself doing extra valves, shooting for the high end of spec. For one, the shims typically don't come in that fine an increment where you can nudge the clearance precisely to the top end of spec, and second, you may end up overshooting or causing some other issue. Further, valves don't necessarily tighten with wear as everyone thinks - sometimes they can go the other way so moving towards one extreme of spec may just be increasing the risk you're going to have to do it again the next adjustment. Not to mention the extra work and expense, especially if you end up messing around with a head you wouldn't have messed with otherwise. If you just have one valve out, I'd just shim that one.
markjenn screwed with this post 12-11-2012 at 11:01 AM