Ok I just bought a new crate motor a few weeks ago and it has been running fine up until a few days ago when it puttered out and died on me in my driveway. Now it will try to turn over but wont make it. I checked to make sure that it was getting fuel and now know that isnt the problem. Ok this is where it starts to get bad.

Ok I'm pretty much a backyard mechanic so I dont really get to do everything the "correct" way. So to check to make sure there was some juice getting to the plugs, I pulled the wire off of the number one cylinder and stuck a screwdiver in it, and placed it up against the headers to see if it would spark when the motor was turned over. I've done this before many times and never had a problem, except this time.

When my buddy turned it over it took a few revolutions then there was a loud BOOM like a shotgun going off. There was a bright light and I could feel a small amount a force blowing back. After my ears stopped ringing I noticed some smoke coming from the valve cover breather. When I pulled it off I noticed the cover was full of white smoke. So was the other valve cover aswell leading me to believe the whole crankcase was.

The motor still tries to turn over like before but i havent got it started yet. I'm not worried about that so much. I just cant stop worrying about what kind of damage I caused from that explosion. If anybody has had this or even heard about this kind of thing happening, could you let me know what caused this and what am I probably going to have to replace inside the motor now.

Thanks in advance for any replies.