oil leak

[redamnavit]

I recently purchased a 1993 240sx with about 250,000 miles on it, so I'm shaking it down to find whatever weak spots I'm going to need to fix. Please excuse me if this is a newbie question...

Today I added some injector cleaner to my tank and was revving the engine in the driveway for a few minutes to try and blow out a bit of whatever's accumulated. Things sounded fine but I noticed white smoke when I held it at higher revs. I figured this was just whatever carbon was burning off and thought nothing of it until I pulled back into the garage and noticed a puddle of oil under the car where I'd had it in the driveway.

The car didn't leak when sitting all week, and after I shut it down it doesn't appear to have continued to leak. I've had it idling for an extended period before and didn't notice any leakage then either.

Anyone have an idea what I should be checking over first?

Thanks.

[NISTECH]

front crank seal most likely