Flathead V8 spark plug colour variation

[David Dunlop]

Mark. Did you plot which cylinders each plug came from? That information can be helpful to the analysis of engine performance as well.

Good plan to check again after a road trip when the engine has reached normal running temps and load for a while.

David

[Richard Farrant]

If the engine was only idling then the black on plugs would denote a rich idle mixture, which is adjustably, also choke might be partly on. When you do a plug check on racing engines, the engine is cut at running speed and knocked out of gear, brought to a halt, then plugs are checked. That way you get a true picture of the plug and can access the mixture or whether the plug needs changing to a hotter or colder type.

[Phil Waterman]

Hi Richard

How old is the gas, modern gas (at least the stuff in the US ) goes bad so quickly that I've given up trying to do any engine tuning without having system filled with fresh gas. Also find that it take an hour or so drive to clean out the engine.

Of course my CMPs have two less cylinders to start with.

Cheers Phil

[Mark Towers]

That's interesting Richard .... I will try not to let her idle long then when I get her back to the shed after the road run .... I'll switch her off as soon as I roll in.

And Philip the gas/petrol is from early start of the year ... so probably on the turn ! Good point !

Many thanks,

Mark

[Howard]

Originally Posted by Phil Waterman

Hi Richard
How old is the gas, modern gas (at least the stuff in the US ) goes bad so quickly that I've given up trying to do any engine tuning without having system filled with fresh gas. Also find that it take an hour or so drive to clean out the engine.
Of course my CMPs have two less cylinders to start with.
Cheers Phil

Phil, Lucas make a 'fuel stabiliser' (or stabiliZer in your version of English) that I can recommend. Prevents the fuel going sour, even over an extended period. Great for ski boats during winter storage etc.