[Capt Kirk]

Ford38. I'm no expert on these flatheads but have an opinion based on my experience with other engines. When taking a compression test, I've been taught to crank till you attain the highest reading. If that happens in 2 revolutions or 12...it doesn't matter. If a valve is sticking, it might not be sticking every revolution. You might get a full compression reading after a longer period of cranking. A vacuum test reveals real-time what the engine is doing. Now, if a valve was burnt or never closing all the way...then yes, it would show on a compression test. A leak-down test is a good thing too. A 5 minute test with a vacuum gauge will reveal a lot.