Hi Steve,
Welcome to the forum. In the upper right of most any page on the BCF, you'll see "Welcome greencar1967" when you are logged in. Just below your name is the search button. I always click the advanced option after clicking search.
Once in advanced, you can narrow your search to just a couple forums like Healey and racing. Select the first with your mouse and hold the shift key with a mouse click to select a second and third forum if you want. (The shift key may be something else on a Mac). Under keyword search, if you type valve clearance, you'll get all posts with the word valve, and you'll get all the posts with clearance. By putting "valve clearance" in quotes, you'll get only the post with that phrase, which should narrow the search down quite a bit. The search defaults to posts made in the last week. I usually set the "newer than" to blank and set the "older than" to 1 month.