icanfixall
Official GMM hand model
Best I can suggest is something was missed with the front water pump gear cover plate. Reason I mention this is you did have a tight block after testing with the block off plates. Then it tested good so you put it on the road and tested it. Now something has failed. I suspect a pushed out timing cover gasket. If you had a Plasma cutter you sure could very easily make a timing gear cover from stainless be using the original as a model. The timing tab is really easy to remove and weld on the new plate or make another one. Might end up a nice cottage business too. These timing gear water pump covers do get eaten up from bad water and errosion over the years. We have seen some really bad ones here too on this forum. Saw one where the member JB Welded it smooth again. Never heard how long that lasted either.