Mark VIII Spark Plug Repair

[FordPro]

I'll try the leakdown method for sure. My compression gauge goes in hand tight and the adapter I put into place to fix the plug hole doesn't allow it to thread in enough for a proper comp. test. Reads way low even for a bent/sucked valve or even shattered piston. Yeah the piston is banged up good from the plug and what ever else. I'm gonna pull the head to inspect, man I need a daily not this bs. Fords shoot plugs because of bad design period, almost no other heads spew plugs like this. Thanx ford engineer scum bags! Yeah it was a big metal noise, not some aluminum shavings. Thanks bro keep me informed.

 

[Right on the Mark]

I'll try the leakdown method for sure. My compression gauge goes in hand tight and the adapter I put into place to fix the plug hole doesn't allow it to thread in enough for a proper comp. test. Reads way low even for a bent/sucked valve or even shattered piston. Yeah the piston is banged up good from the plug and what ever else. I'm gonna pull the head to inspect, man I need a daily not this bs. Fords shoot plugs because of bad design period, almost no other heads spew plugs like this. Thanx ford engineer scum bags! Yeah it was a big metal noise, not some aluminum shavings. Thanks bro keep me informed.

Even when you blow out a plug the piston should always be clean. The plug cannot hit the piston. I am now thinking you might have had a valve seat break up. Thats the only thing in there thats steel and can break up on top of piston. Like I mentioned in this thread Escort engines drop the #4 seat out of the head ALL the time. How did the plug look when you took it out? Was the end clean or gap shut and all beat up? Unless like you mentioned you broke the piston top ring land. If you did you will now see nice sized chunk missing with bore scope.

 

[Right on the Mark]

I'll try the leakdown method for sure. My compression gauge goes in hand tight and the adapter I put into place to fix the plug hole doesn't allow it to thread in enough for a proper comp. test. Reads way low even for a bent/sucked valve or even shattered piston. Yeah the piston is banged up good from the plug and what ever else. I'm gonna pull the head to inspect, man I need a daily not this bs. Fords shoot plugs because of bad design period, almost no other heads spew plugs like this. Thanx ford engineer scum bags! Yeah it was a big metal noise, not some aluminum shavings. Thanks bro keep me informed.

First thing I would do is pull plug bore scope piston then do leak down. That will tell you if engine is F'ed or not. No need to pull head if piston is broke and then took out head. Cheaper to throw junkyard bullet in.

 

[FordPro]

Yeah leak down test proved it, heard air coming from crankcase slightly, also from the exhaust. I'm guessing most of the air was exiting out the exhaust valve destruction but enough made it past the piston to get heard out the dipstick tube. Leak down is a real pain to do by the way, just finding the top of the number two piston travel was tough. I posted a quick reply earlier and I don't know where it is so i'll say thanks again bro for the advice. I don't really know what direction to go now, I don't have the money or time to be buying a motor, not around here anyway, for a daily driver that I need right now. Maybe this is the end of the Mark : ( I don't get it though I wasn't at redline or anything just going down the freeway.

 

[chris2523]

i'm not understanding how the plug could go farther into the block than when its screwed into the head? seems unlikely..

and when the plugs blow out, they are, well, out. not in the block..

 

[Right on the Mark]

Yeah thats the thing with this "the plug can't hit the piston" thing, yes it can, when the threads strip completely out the plug will enter the c. chamber like mine did. I will take pics to prove this. IMO this causes serious problems, Like mine, oil now enters my c. chamber from the lower portion of the cracked piston I mentioned earlier. I'll take pics with the head off. Yeah I understand this is a worse case scenario but it could happen to anyone. I pampered my car for real, yeah I get it, go forged all day wether eagle aftermarket or whatever I get it. ; )

I'm not stating it can't happen but I still don't think plug hit piston. I just went out and mic'ed plugs. The thread dia is .545 then up father right above plug seat the dia is .615 and that length is only .300 more for it to drop into chamber. That would mean after plug blew out hole would now be .545 then next the plug would have to go up and down so much to open the hole up to .615 for plug to only fall .300 then it this the hex of the plug with cross large are is .715. Not saying your lying or anything just weird.

 

[Right on the Mark]

Yeah thats the thing with this "the plug can't hit the piston" thing, yes it can, when the threads strip completely out the plug will enter the c. chamber like mine did. I will take pics to prove this. IMO this causes serious problems, Like mine, oil now enters my c. chamber from the lower portion of the cracked piston I mentioned earlier. I'll take pics with the head off. Yeah I understand this is a worse case scenario but it could happen to anyone. I pampered my car for real, yeah I get it, go forged all day wether eagle aftermarket or whatever I get it. ; )

If any part of your plug hit any part of your piston it could ONLY strike the CENTER of the piston only.

 

[Right on the Mark]

i'm not understanding how the plug could go farther into the block than when its screwed into the head? seems unlikely..

and when the plugs blow out, they are, well, out. not in the block..

The spark plug boot and or COP can kinda keep plug in the area and not "blow" it out and off engine because we have plug covers. Where then comp will blow it up then piston going down will draw plug back into engine. I can't see that happening where plug goes into chamber unless you maybe drive car for a long time with plug blown out. Like mentioned you would have to "bore" out the plug hole .070 for that to happen.

 

[94m5]

I had my old 98 blow a plug out, running down the interstate, with enough force to shatter the COP cover. Scared the hell out of me, but I was able to just thread one back in, and install a new coil to get me home.


I ordered the time sert kit and repaired all 8 holes.


Do it right the 1st time.

 

[Right on the Mark]

I had my old 98 blow a plug out, running down the interstate, with enough force to shatter the COP cover. Scared the hell out of me, but I was able to just thread one back in, and install a new coil to get me home.


I ordered the time sert kit and repaired all 8 holes.


Do it right the 1st time.

I did not know if it would punch thru the cop cover. Good to know.

 

[ford nut]

You most like bent a valve not dropped a valve. That piece you heard clanking around got stuck under closing exh valve bending head. Then it went on its not so merry way.

+1
No way in my mind that plug can get sucked in.
maybe a part of it.... if the car was driven and hung up on the exh valve like Frank stated.

 

[purevilpleasure]

I've had 2 of my 4.6's have plug issues. My 98 Expy bent a valve.....blew up the spark plug and scored the side of the block to the point of no return. Ended up with a reman for that one....

My F150 blew one out on the way home....I pulled over and found the plug laying on the ground next to the truck....I repaired it with a Save a Thread from Napa...worked well for about 6 months....now I have another head sitting in the shed ready to put on it....guess what happened to the save a thread insert? It's now spinning in the head.

 

[Right on the Mark]

I've had 2 of my 4.6's have plug issues. My 98 Expy bent a valve.....blew up the spark plug and scored the side of the block to the point of no return. Ended up with a reman for that one....

My F150 blew one out on the way home....I pulled over and found the plug laying on the ground next to the truck....I repaired it with a Save a Thread from Napa...worked well for about 6 months....now I have another head sitting in the shed ready to put on it....guess what happened to the save a thread insert? It's now spinning in the head.

If the plug blows out clean there should be no problems but yes if the plug gets busted up and drops its pieces into chamber "problems"!

 

[FordPro]

Well no need to pull the head. I heard air coming out of my crankcase during leakdown test. : ( I think you were right about the valve seat problem. I can't really get a good shot back up at the head with the borescope. Thats what must have chewed up the bottom of the plug. I thought the plug entered further into c.chamber, but you guys are right that isn't likely. This really did come out of nowhere, I was cruisin on the freeway when this all happened, not at redline or doing donuts or anything. I don't get it. Thanks for the quick replies and suggestions. I'm still trying to figure out what to do, times are hard and I can't afford to blow my paycheck on this.

 

[FordPro]

Yeah you were right 'right on the mark' about the plug, I thought it could enter further into c.chamber with no threads left but I don't think so now after re-inspecting. Maybe it was the valve seat issue you mentioned because the plug was chewed up. The piston was marked up at the bottom near the cyl. wall with a jagged little crack. I did do the leak down and I heard air coming from the dipstick tube and out the exhaust. That leak down is a real pain on the number two cyl. with these problems. Motor is K.I.A. I don't get it, I wasn't at redline or even close to it, not spinning donuts just going down the freeway. The COP kept the plug from leaving, but in hindsight maybe the valve seat debris knocked out the plug went it was bouncing around? I don't know. The metal clanking around didn't really happen till after plug repair but I used vacuum and borescope to ensure no debris was left in cc. I don't get it. This was my dd, and I don't have the money or time for this. To bad because I loved my mark. Thanks for the quick advice guys.