This is a question better suited for Thomas than me. My knowledge on the subject is rather limited compared to him. But I will take a stab at it.
I don't think too much fuel will go into the engine if you don't open the throttles when you crank the engine over. If you are really concerned, you can always disconnect the fuel line and plug it off. You need to make sure you throughly check the line fittings, JIC, SAE, Tube, etc. and then put on the appropriate plug. Of course, if your carb is working correctly, then the needle seats will have shut off the flow of fuel to the carb so I am not sure this will acomplish much either.
Of course, if your needles aren't seating, then I have seen truly outrageous amounts of fuel being dumped down the engine--maybe this is where your fuel in the
oil problem is coming from.
More importantly--safety.
Be very careful not to pump raw fuel anywhere and make sure you don't have any leaks. I have seen more than my fair share of "haircuts" from leaking fuel lines, carbs catching fire and giving you an unexpected hair cut...or worse.
Soak up any raw fuel with some rags and dispose of them properly and away from any sources of ignition...water heater pilot lights, spark plugs, wires, hot parts, etc. Don't laugh, I have put out more than my fair share of engine fires, (fortunately, none of them were my fault.) I once put out a fire at BYU where an
oil pressure line came apart and sprayed
oil on the exhaust manifold...you wouldn't think it would have went boom, but it did. What a mess that one was. Fuel is way more dangerous than oil.
Always keep a friend and a fire extinguisher handy when working on fuel systems--and make sure it is the right kind of fire extinguisher.
Be careful and have fun. It will all be over soon and you will be driving with a big smile on your face.
David
