After you get the engine running good, dribble a "urine stream" of water down the primary venturies, going back and forth between them fairly rapidly. I use about a gallon of water, and have the engine at fast idle--1200+ rpm. This will "steam-clean" the combustion chambers. All the carbon will be gone when you're finished. This works as well as--or better than--petroleum-based "top engine cleaners" and you won't have the neighbors calling the Fire Department because of all the smoke. Change oil afterwards, there will be moisture in the oil pan.
Inconclussive, nothing out of the ordinary really. If you had bent a valve there would be definite marking on piston surface, I say the porcelain broke off causing the gap to close and then you had a grounded plug not sparking so it ran like a turn with only 7 cylinders.......re-plug and burn rubber my friend!
If you had severe enough detonation to knock the material off the piston tops, you very well could have more damage just out of sight. I've seen engines run with much of a piston skirt along with most of the rings sitting in the oil pan run fine at plug change, only to oil foul the plug in a week (from the oil getting past the rings into the chamber). If your fouling returns, suspect more damage. There's always bearing damage potential with detonation problems. Keep an eye out for any oil pressure change from normal. I've also dealt with Motorcraft plugs listed as covering several heat ranges in a GM and seen too hot of a plug cause detonation/preignition damage.
Ford hasn't owned Autolite since 1973. You really think those plugs are that old? Motorcraft = Ford I say the gap closed, distorting the ground electrode, which applied force to the center electrode, which distorted and broke the porcelain.
Whats these two stripes? It looks like the piston crown is cracked or is this just a shadow illusion?
It doesn't matter that Ford hasn't owned Autolite since 1973 . And I don't think those plugs are that old . What I'm saying is Autolite and Motorcraft plugs are designed for Ford vehicles . Champion plugs are designed for Mopar vehicles and AC Delco plugs are designed for GM vehicles . I am referring to vehicles of our cars vintage .
Piston marking showing which direction the piston should be installed. The divot goes forward. Some pistons have a dot impressed into the piston crown. These have the larger "slice" taken out of the edge of the dish rim. Oooooo Kay.
Had this happen on a 455 many years before bore scopes ect were invented. Never did find out what caused it but the electrode on 2 of the cylinders would get smooched flat. Gave up on trying to figure it out and just put non foul adapters on it. was my only trans to and from work. ran it that way until I sold it a yr later
Sorry Schurkey but I guess we will have to agree to disagree. I was just stating facts I have seen through out my career as a Mechanic . Have a nice day . Oooooo Kay ????
I don't know if it is the focus or what, but those piston tops look pretty nasty to me. I've seen detonation do some pretty drastic damage to spark plugs. I would look at the ignition timing. One of the most common mistakes made is believing all your advance is in when it isn't.
Larry, what do you mean by "nasty", would you say it`s too rich in gas and that`s why "crusty" because it`s not burnig up correctly? I`ll check on the ignition soon, will let you guys know. Thanks for all your input so far, really helpful. Jens
When an engine operates with detonation, the piston crown can get a sand blasted appearance. I really can't tell from those pictures, maybe someone else can, but with that kind of plug damage, I would be looking at my ignition timing.
