Have an odd situation with the built 350 in my 75 Vega - the appearance of my spark plugs ( photo below ) seems to indicate the engine is running lean, but the tailpipe is sooty and very nearly black. Also, the threads on the plugs are wet – before you say it’s the valve cover gaskets leaking, read the following which makes sense to me.
“While it may look like dirty oil, it isn't, this is unburned fuel that all the lighter elements in the fuel have boiled off leaving the heavier hydrocarbon components behind. This is not unusual to find even on race engines. I wouldn't have known this myself if I hadn't run across the explanation from a very respected pro engine builder on another site. This "fuel" is here because the seal(tapered seat or gasket) is above the threads but the threads themselves are shielded from the actual combustion process. Almost sounds crazy but it is true.“
The likelihood that the wet look is from unburned fuel also seems to contradict the lean situation that the appearance of the plugs indicate???
Any thoughts?
Many thanks,
Nick