Is there a good site or document with pictures on reading plugs? I had an old Chevy HP magazine with a good article in it but cannot find it.

 

Check out NGK's website in the link below. Pretty good descriptions and be sure to check out all five pages listed at the bottom

http://www.ngksparkplugs.com/techinf...000&country=US

 

Here's some others:

http://www.maxracesoftware.com/spark_plugs.htm

http://www.dragstuff.com/techarticle...ark-plugs.html

 

Plug reading is becoming a lost art. With unleaded gas and high energy ignitions plugs just don't color like they used to. I know mine is very rich but looking at the plugs they look great.

 

This is intresting. When I had my car on a chasis dyno, they said it was running rich, so they dicked around with the carb to get it to the optimum a/f ratio, but it lost power. So they changed it back to a little rich and maximum hp. The plugs are VERY clean.

 

Having fairly recently (sort of!) had to change from leaded to unleaded this was immediately apparent. I've heard unleaded burns a bit hotter, etc, etc, but whatever it is, the plugs definitely do not show the color differences that they used to when running leaded. I've just finished (finally!) getting my bike set up for unleaded & a jet/setting change that used to have a marked difference on the plug color now has very little effect eg. going up one size on the needle jet has the same effect that slightly richening up the idle mixture used to, though there's a big increase in mixture richness. A couple of weeks back I finally got the mixture spot on from idle through to WOT & the plug color is only very, very slightly darker than it was the previous week when I had it set so weak that bad pinging was occuring. Even then, the plug color was only slightly lighter than the ideal color, not the white, blistered appearance shown in manuals (eg. any Haynes manual shows pics of plugs colors).
Reading plug colors can still be done, but you've got to have a keen eye & a good idea of the correct plug color for the engine (different types of engine could have slightly different colors of plug tip when set up correctly using leaded fuel, I doubt if there's any difference that can be seen with unleaded, there may be, but I've given up looking at plug colors these days!). What you'll see is the same as shown in the pictures, but the color changes will be much, much less pronounced. Just to make things worse, an engine that is burning a very slight amount of oil seems to darken the plugs more than running overly rich does. What a pita! I've come to the conclusion that the only way I'm going to know for sure if the Vette mixture is OK is to fit a wideband O2 sensor, or use a garage's exhaust analyser. The reason for this is that after 25 years of having my bike, & working on countless others, I was able to set mixtures purely by looking at the plug colors at certain throttle openings/loads. After recently frigging about trying to finally get the mixtures right on my own one, I've come to the conclusion that I haven't a clue anymore!!! I had to do it "by feel" and ear, only looking at the plug colors out of interest (sometimes the changes were so small that they could have been imagined, rather like comparing shades of paint when one area of it has been in the sun for a while & another hasn't). A dark tan color used to mean that it was running on the very slightly rich side of spot on, now it means it's running very rich, a light tan used to mean that it was running on the very slightly lean side (which seemed the best mixture for performance), now, going by the awful pinging I had, it means that it's lean enough to punch holes through pistons. Err on the rich side if you're not sure & remember that it's the color of the plug tip (the ceramic) that you're interested in, not the "ring" on the outside.
As for what happens when you change the heat range of the plug, aaaaaarrrrggggghhhhhhh! Why does life have to get so complicated, it was easy with leaded fuel
I'm not sure about high energy ignition systems having as much effect as unleaded fuel does on plug colors. I also run an old 500 fitted with a 60's Lucas points & coil ignition (I'm a masochist!) & the plug colors look the same as my Bonnie's (now it's correct), which is running electronic ign & high O/P coil. Similarly, I didn't notice any difference in plug color after swapping out the stock Lucas system in an MGB for a high O/P electronic one.

 

You actually can “Read” plugs with unleaded fuel, but as stated the changes are less pronounced which makes it much harder. Another couple of things to keep in mind: Different brands of spark plugs will be easier or harder to “Read” based upon their construction. Also, different brands of fuels with “Read” differently based upon the additives they put in them.

 

Thanks for the info guys. I am running autolites and Shell premium with a full MSD setup. I have not done a plug reading yet but plan to this weekend. I am thinking I am a little on the lean side but not sure. I have the stock advance springs in the MSD distributor and I had to back out the mixture on my Mighty Demon 850 annular one full turn. Other than this I have not done any real tuning. The car puls strong to 5500 with no sputtering or dead spots or smoke. The only thing I am getting right now is run on and smoke through the top of the carb after I shut it down at operating temp.

Thanks
Wade

 

Wade,

Check your intial timing, and idle RPM as both of these (as well as heat) can lead to a run on situation.