This is topic Blowing spark plug out top of engine. in forum Tech Talk at Northern California Ford Owners  .


To visit this topic, use this URL:
https://californiafords.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=6;t=012905

---

Posted by BlacksheepMod50 (Member # 2378) on :
 
I have now blown the same spark plug out the top of my head 2 times in the past 3 days. I am assuming I've simply just stripped out the threads in the heads of my aluminum POS crappy ford-casted heads. I know there are descrepencies in the way which the heads on the 4.6's are cast and sometimes there are plug holes which have as few as two full thread rotations for a plug to grab onto because of just a bogus cast, while other cly's may have 4-5 full threads. Can anyone think of any way to remedy my problem or am I just stuck with having to pull my heads, get them helicoiled and just be done with it? If I do that... time for a bigger port job on those heads
 

---

Posted by Joooestang66 (Member # 2828) on :
 
You can heli-coil them while theyre on the car. The kit is alot of money, around $600-800. I'd ask around at some shops or more specifically Ford dealers to see if they have this kit. I doubt an indy shop would have it since the kit is meant specifically for Ford modular engines. The part itself is around $3.00 for the heli-coil, you should expect no more than 1.5 hours in labor from a dealer to do this job since all the spark plugs are accessable.
 

---

Posted by asskickn88 (Member # 4957) on :
 
I have heard about this happening if the plug is changed and doesnt get tightened all the way....
 

---

Posted by BlueOvalRacing (Member # 1531) on :
 
Joe, do you guys actually repair them in house?
We don't even bother, we just sell them a new head (or heads)
 

---

Posted by BlacksheepMod50 (Member # 2378) on :
 
Sell them a new head just because of the time involved in heli-coiling the head? Seems a bit extreme, because if you sell them a new head, then the heads have to come off the car anyway. At that point, heli-coiling the head isn't that hard to do. Some of the plug holes in my head are already heli-coiled from a previous install and it hardly cost anything because of the ease to do it. If I have to take the heads off, I'm just going to heli-coil both heads.
 

---

Posted by stangnut (Member # 5937) on :
 
i have never heard of any head aluminum just having a couple of threads for a spark plug to hang on to .of any casting ! all alu heads take at least double the threads of iron heads on purpose to decrease that problem of pullin out.but i have seen the wrong plugs in heads before.if you heli your self . make sure the piston is almost the way up .not all the way so when your tap goes through it doesn't hurt the piston.if u leave the piston down u can't get all the shavings out an the peices of metal get stuck between the piston an its walls, u'll be boring your motor over soon.
 

---

Posted by wilit (Member # 3367) on :
 

quote:

---

Originally posted by asskickn88:
I have heard about this happening if the plug is changed and doesnt get tightened all the way....

---

Spark plugs have torque settings too. If you don't torque them down right, they will blow out.
 

---

Posted by BlueOvalRacing (Member # 1531) on :
 
All modular motors have had this problem, because Ford only gave about 4 to 5 threads total for the plug to grab on to. We see probably 3-4 engines a month that have a plug blown out. And it wasn't caused by under/over tightening, just a bad design. The new 3 valve heads are having a problem with the plugs breaking off at the top of the threads on removal - the engineers are scrambling right now to find a fix.
 

---

Posted by BlacksheepMod50 (Member # 2378) on :
 

quote:

---

Originally posted by BlueOvalRacing:
All modular motors have had this problem, because Ford only gave about 4 to 5 threads total for the plug to grab on to. We see probably 3-4 engines a month that have a plug blown out. And it wasn't caused by under/over tightening, just a bad design. The new 3 valve heads are having a problem with the plugs breaking off at the top of the threads on removal - the engineers are scrambling right now to find a fix.

---