Actually I used a stethescope to listen didn't really tell me much tho because the motor is so loud. Now I'm running into another issue. Engine ID. I had a reliable source tell me that I should be able to find the number on the flange that sticks out past the cylinder head on the passenger side front of the engine block. The flange was there but it is blank... I also found a source on the internet that said to look just above the timing cover for the #.. I found one, it is "10427xxy" but I have not been able to find a resource that can decode it. I've serched online and called the local gm dealer and fuond nothing......