I have a 82 e-350 with a 460, She has smashed the plug electrode two times now on the same cylinder, this usually occurs when the motor is under load . so far no other damage has occured to insulator only tip of plug. She has 87000 miles and runs great after plug replacement, any suggestions as i have already put in new valve springs on this cylinder.

 

maybe put a second washer on the threaded end so it doesnt do down into the cylinder so far.

 

you could put an anti-fowler in that plug hole.its just a lil spacer thing that gets the plug up out of the hole.or slowly puor water (about a qt) down threw each side of the carb while it at a fast idle.the heat of the cyl fireing with the water will act like steamcleanin the top of the pistons and remove carbon.some times it dont work the first time but waters cheap do it again

 

First make sure you are using the correct plug for that year and model engine. If you are just using what came with it when you bought it, it is possible the previous owner substituted a plug with incorrect reach.

I would wonder why one plug is getting the electrode smashed. Usually this means either you dropped it, but I assume not, or the piston is hitting the plug. This is bad and needs to be checked. Maybe you have a rod bearing that is getting too loose or a stretched rod? Hard to explain a smashed electrode on a normal engine. Any rattling sounds coming from the engine?

This kind of an odd problem. Which usually means something is wrong.

Good Luck,

Jim Henderson

 

I doubt that there could be enough carbon build up on an engine with this low of compression to let it hit the spark plug. If you don't hear anything rattling around in that cylinder then you have got to have the wrong spark plug in it. The simplest thing to do would be to swap a spark plug out of a different cylinder and see if the problem moves. If the problem moves then you have a plug problem. If the problem doesn't move then you have a major problem with that cylinder. you could also take the offending plug to a parts store and ask to see a plug specified for your engine and compare the reach.

 

This problem is usually associated with one of 2 other engine problem, rod stretch or rod bearings badly worn (that is if the right reach plug is being used). Check for the proper plugs first, as jim said.

 

You would think he would be hearing something if there was bad bearing wear or rod stretch. He didn't mention hearing any noise and he says it only does it under load. I would think the piston would be lower in the cylinder under load and higher in the cylinder while in the float position, Or do I have it backwards?

 

I have no noise but i did start getting lifter noise so i just put in all new lifters and replaced the valve springs both, on that cylinder plus a new carb as the original was burnt from a previous carb fire not under my ownership I am currently considering removing all emission air pump crap as that seems to cause these carb fires and now since the lifter tick is gone i will keep everyone posted as to the plug issue, The motor had no associated noise when it would destroy the plug and i was thinking a weak spring or bad lifter so we will see and thanks for all the suggestions also put in new plugs and cross referenced back 5 years older and newer and the 460 plugs are no different in lenght

 

I drove it the other day and it still has lifter tick but only at idle and only on cylinder #5 which is yhe same cylinder that was destroying the plugs, I drove about 10 miles but was hesitant about getting into 4 barrel until new lifters were in for a while so hopefully it needs a little adjustment but i think you guys might be right about lower end problems we will see Thanks

 

Put a short plug in that hole most any short 14 mm plug will do for this test and see if the tick goes away if it does then there is piston interference issue could be a bad wrist pin or the top of the piston is fixing to come off. yes a loose rod can do that but usually if their that loose it will really have a knock. Number 5 would be the front clyinder drivers side.you might be able to look in the sparkplug hole and see if you see any bright metal when the piston is at tdc.

 

I have a 429 that had the exact problem, the cause was a piece of piston.
the piston had broken off a piece and it was floating in the cylinder.
pull the head and take a look

 

im thinking there might be debris in there, in know a guy who dropped a carb nut in his motor and left it, it made a ticking noise like a lifter cause it imbedded itself in the top of the piston and was barely touching the head on each upstroke...on another note, early rod bearing wear will cause a ticking noise before it turns into a knocking noise....i dont see how bad lifters or valves could cause plug damage, i would only think that could only cause valve or piston damage...

 

This is the craziest problem I have ever heard of. This is a low compression engine. I have a hard time believing that piston could be hitting the plug no matter how stretched the rod is or how bad the bearing is. I can't imagine anything that could be loose inside of that cylinder that could survive the combustion temps and be dinging the plug. It can't be anything is the valves because they can't hit the spark plug. I did have a piston break in half one time just above the scraper ring on a racing engine. The darn thing kept working Ok. It has been so many years ago that I can't remember the noise it made. I know it did make a noise because that is why we tore it down. I was really shocked when I popped the piston out of the cylinder and the top half of the piston fell off. I just goes to show you that anything can happen.

I think I would take the plug out of that cylinder and put a thin screwdriver or rod of some kind into the spark plug hole and rest it on the piston. Put a little pressure on the screw driver and turn the engine over by hand and see if you can feel any unusual movement in the piston. If not, something has to be floating around in that cylinder. See if you can figure out some way of seeing into that cylinder or put a clothes hanger in there and move it around and see if you can feel anything. If there is, you need to get it out before it does more damage. It possibly could be a broken tip off of a spark plug. I think I would leave the spark plug out of the cylinder and start the engine. Rev it up a few times and see if it would blow whatever it is out. Just a suggestion