to me it sounds like your carb flooded and the gas made it past the rings into the crankcase. ive never seen/heard a fuel pump do that.....doesnt mean it cannot happen though.

 

that could very well be. do you know what the fuel presure is now?

 

did you remove the tank and clean it out that way?? also just because the carb was rebuilt dont mean the float cant stick. what i would pull the tank if you haven't and clean it. if you did then take the top off the carb and check for gunk. if no gunk then just for now hit the carb where the floats are with a piece of wood to jar the floats (usually works) then fire it up if it stays running. shut it down. change the oil with 4 quarts of oil and one quart of tranny fluid why tranny fluid? its very high in detergents run it for 250-500 miles then change it to strait oil and your filter too. if jarring the floats dont work try putting some motor oil down the Cylinders not a lot maybe an ounce each then turn the motor over without the plugs for say....7-10 seconds but no more than that. re install the plugs.(im a autolite guy) and then try to start it again. gl

 

yes that has happened to me a couple different times. where did the pop come from? if it came from the carb i would say timing. if it came from the tail pipe id say your carb is still flooding. thats just from what happened to me. the carb would flood filling up the cylinder out an open exhaust valve and load up in the muffler. its like shutting your car off letting it coast and starting it up again. you get a loud bang and everyone ducks.

 

The first thing that you have to do is get that gas/oil out of the crank case!!!!!

I ended up buying a 340 motor for vary cheap becouse it was Quote" Posesed"!!!! the valve covers blow compleatly off!!!!! the valve cover bolts were still in the head.......but nothing ELSE.

That 340, was a vergine and is now the .020 bored 340 in my Cuda for the past 11 years

You need to get ride of that gas in your oil now!!!!! then try and get it to start.

If the gas has ran down the piston,and washed all the oil of the rings(carb leaking fuel...gas)then there vary well could NOT be enough compression to start................as has already been mentanded, squirt some oil thru the spart plug hole and it will probably start.

as far as the fuel pump being the problem......there is a drilled hole behind the diaphram, so if it goes bad, it runs down the out side of the block..........If this hole didn't get drilled or is plugged with grease or something........it will go into the crank case.

 

oh yes specially if it has the crappy nylon fiber covered teeth. on the gears