Comment Re:The answer appears to be a yes. (Score 3, Informative) 297
Most starters aren't strong enough to bust up a wrench or socket. Take out a plug maybe, possibly bend a valve, but in all likelihood, the motor would turn the engine till contact and stop.
That is assuming you are hitting the engin with the starter before hooking up the fuel and plugs. Which is usually a good idea to get the oil pump primed and heads lubricated firing it up.
That said, I have a number of wrenches that could easily fit in a cylinder with the piston at BDC. A GM 350 for instance, has a 4" bore and 3.48" stroke. On the diagonal that gives you over 5 1/4" clearance at BDC, not including the combustion chamber in the head.
9-11mm wrenches and 1/4" wrenches are common tools under the hood. Wiring brackets, trim plates, grounding lines, battery terminals, oil pan bolts, valve cover bolts, etc... They all fall into that size range.
-Rick