[Jim Brierley]

There are some very good answers above! I ran a 7.5:1 Cyclone flathead for years with no problems. Included were several trips from SoCal to Las Vegas to visit Ed Winfield. The engine was a B/C, stock oiling, babbitt by an unknown guy but done at Trade Tech school in L.A., so of unknown quality. It is not compression, but detonation that will ruin babbitt. Something to think about, ... when 2 Model A's are traveling down the street together at the same speed, one totally stock, the other with high compression, dual carbs, etc., they are both using the same amount of power, so both have the same amount of pressure in the cylinders. At that point they are totally equal. Now if they both put the pedal to the metal, the non-stock A will put more pressure on the bearings and will pull away from the stocker. With oil as a cushion, the bearings will not be harmed.