Flathead V8 spark plug colour variation

[Mark Towers]

Originally Posted by chris vickery

I would think bad ignition to said spark plug. Could be plug, wires, or distributor. If the caps on the distributor have badly worn contacts you will get erratic ignition cycles.
It may also be from sticky or worn valves as well.

Thanks Chris,

I appreciate your input.... I will investigate all of the above and see if I can remedy the issue.

I know I have cylinder missing but I have conducted a pressure test on all cylinders and observed a reading of 95psi in all 8 cylinders. I have a new distributor cap, rotor arm, new HT leads and spark plugs .... I've only driven 500 miles from fitting new pistons and rings .... the valves are original as they looked healthy.

So looks like it could be valves then ? .....

Many thanks

Mark