LET IN THE LIGHT(ER)
When vacuum checking 4 valve per cylinder heads, its hard to tell if its both or just one valve that’s leaking. Use your vacuum tester and one of those long inexpensive BBQ or candlestick lighters. Hold the lighter close to the valves and the leaking vacuum will pull the flame in, making it easy to tell which one is leaking. Just make sure there is nothing flammable nearby.

Dan Matton
D and D Auto Machine
Bloomington, MN
March, 2016