Valve tappet adjustment

[Phil Waterman]

Tony- While checking the valve adjustment is probably a good step anyway. Have you done or thought about a leak down test using compressed air?

This is one of my standard diagnostic test prior to start tearing things apart. It is done by introducing compressed air through the spark plug adapter for your compression gauge. Each cylinder is tested at or near top dead center for that cylinder, with vehicle in gear brake on this is so the engine doesn't try to turn over. I generally set the pressure regulator at 50 PSI apply the pressure.

Listen for-

• sound of air leaking in adjacent cylinders - blown gasket possible
• sound of air leaking from carburetor - leaking intake valve
• sound of air leaking from exhaust- leaking exhaust valve
• sound of air from oil filler or crankcase breather- bad rings

You may need to vary the air pressure but if you have a real problem it will be very noticeable.

When you check the valve clearance take note of those that have decreased and if any of them have gone to "0" of course that indicates real valve wear.