74 450SLC rough idle solved!

[deaconblues]

Yet another "rough idle" post. Maybe this will be helpful to someone.

Been living with "lumpy" idle for the last few months. Not horribly bad, but definately annoying. At various stages have replaced/checked, points, plugs, wires, cap, rotor, timing, EFI sensors/mixture adjustments. While improving other aspects of the car's behavior, mediocre idle has remained.

Decided to check valve lash this weekend. Found all exhaust valves somewhat tight, a couple perhaps more than 0.001" off. After setting them all at cold spec (0.008" ex, 0.003" in), I find the engine now idles like glass. Idle speed also increased, had to dial it back down using the idle air screw.

what a difference!