Carb Tuning

[aj81spider]

I have been driving my 1974 (mostly restored - lots of interior work left to do) and getting the engine dialed in little by litte. Today I noticed that the idle was high, so got Brad's engine maintenance writeup and tuned my carb. I got the idle down to a respectable 800-900 rpm (per my tach, so not perfectly accurate).

The idle mixture screw didn't do too much but I positioned it as best I could. Then, per his manual, I took it for a spirited drive (ran well) and pulled a plug to see if it was too rich, lean, or just right. Here's a picture of the plug:



I'm a complete novice at this, and other things that I thought have looked good (my throwout bearing is the most painful example) turned out not to be. I can see brown on the plug (OK) and white (lean). So what's the verdict? OK or lean?

Thanks for the help ahead of time.

[carl]

Plug looks fine to me. I was told that when we went to unleaded gas that plugs could no longer be "read". In any event, plug reading is for full throttle which means hard on the gas and then killing the motor and coasting in neutral to a stop to check the plug....plug reading at idle does not accomplish much. If the insulator was black I'd say you were way too rich, a white insulator these days is not an indicator that you are dangerously lean.

Other opinions on this will, I'm sure, be offered.

carl

[seabeelt]

I'm no expert, but it looks lean to me. You could always take it to an inspection shop and have them run an emissions test. How is the temp???
r/

[aj81spider]

The temperature seems OK - it stays steady at around 190. The fan comes on and off.

Once I fix my alternator problem I'll try letting the idle mixture screw out a little and see if it changes.

What would the impact of lean on emissions be? A car this old in Massachusetts is emissions exempt - so I don't have a baseline for it.