After 5 years of trailering my 93 Sunbird (Ford 5.0 V8), I finally bit the bullet a bought a slip for it. Put the boat in around June, and just pulled it out to bring back to the house for the winter. I drained the block and exhaust manifolds as cold weather is forecast here in TN. When I went to drain the Cobra, I noticed the left side vent screw is missing. I know it was there when I put it in the slip, so it must have loosened and fell out while running/sitting in the water. My question, could running the drive without the screw in place have damaged anything? Thanks in advance.