I have replaced the plugs with Autolite 26's & to my surprise, no ping. I have 92 octane in it now. Will be curious if I will have the same results with 87. I am surprised that no one on here recommended trying hotter plugs.

 

Hotter plugs usually cause more pinging problems. How do you know that the Autolite 26 is a hotter plug than the Motorcraft Afs-42c?

 

Maybe your truck just likes Autolite spark plugs better than Motorcraft. I personally use only Autolite in my engines.

 

strokin,I've had this problem when replacing my dist.either used or rebuilt,replacing the vacum pot or egr was'nt workin.In each case these distrubutors will over advance upwards to 60 degrees.We have bought dist. for 70's f-350 and sometimes this works.car dist work at low rpm,so that there's quick advance,this won't work in a truck.An old fordman racer that i use to know would take my dist. apart undo the centrifugal advance springs pull the wire clip out under the felt oiler in the center of the main shaft,pull it up, turn it 180 degrees to the other gapstop.If he went to the wider gap, he would run without the vacum advance if total advance was around 40 degrees.If he found it already on the wider gap he'd go to the narrow gap and start trying different vacum pots.remember after you do this you have pull the whole dist. up and restab it in the engine 180 degrees keeping your vacum pot in the same position.I always put the engine on tdc #1 cylinder before I start.Sometimes the little tab had small piece of hose on it to limit advance travel.these most of the time are gone which will make over advance.He built me a 460 for my f 150 which had no problem in kansas.took it to colorado hunting loaded down,it pinged.got to durango fliped the dist.guts around 180 degrees,unhooked the vacum advance timed at 12 degrees,total advance was 42. no ping,13 mpg in the mountains.10 mpg in kansas. you need some vacum advance for fuel mileage. I got a couple trucks this way ,sometimes you got replace those tired springs and stuck wieghts.msd and some of the aftermarket hei for ford work well if you are willing to tune.

 

Standard Autolites were 25's. Parts store person said 26's were hotter. That's what I got. I haven't pulled one to look yet. I am going to do that now. Thanks!

 

I pulled a plug. They look real good. Light tan. My goal now is to get this thing to run on 87 octane. Is it really true that a hotter plug will increase ping? I stepped up one step hotter & the ping stopped. Granted, I had the motorcrafts in there before the autolites. If this is true, sounds like I should go & get a set of Autolite 25's? I will probably get a tank of 87 first. Any opinions?

 

Another factor can be the carb. That 1406 is a bit lean out of the box, and running lean can also cause pinging issues. Look at the charts in the book for the carb, and think about trying to increase your cruise mixture 1 step richer.

 

Just looked it up. With Autolite plugs, the higher the number the hotter the plug.

Whatever caused the decrease of pinging, it is unlikely that hotter plugs brought it about.

Carbon deposits, overadvanced timing, lean mixtures, excessively hot plugs, overheating can all contribute to pinging.

Changing the plugs may have dislodged a bit of glowing carbon. (?)

 

I would not get a full tank quite yet.

 

Interesting! I guess for 10 bucks I may as well get a set of 25's & try them. From the sounds of the opinions here, I should have more luck running 87 octane with 25's than 26's, right?