I know about the "old farmers tricks". They work fantastic on John Deeres and high mileage tired stock stuff. If you want a performance engine to perform, dumping anything down the carb, in the fuel tank, or down the valve cover into the crank case is not going to do any more than bandaid it. It's all fresh. Fix it. A leak down will tell you a lot, yes. Not a compression test, a leak down. It's easy to do, you don't need the block re-honed if it was done decently. You just need some good file-to-fit rings, the gaskets, and some time. Then it's repaired.