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PI HEAD QUESTION

 
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Old 11-06-2011, 01:57 AM
paul
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PI HEAD QUESTION

OK I am confused. Can someone answer my question about my cylinder heads and plug torque. I have a late build 2001 F-350 with the 6.8 liter V-10. I was under the impression that all the 2 valve heads had the reduced thread count and are in danger of spitting plugs. Now as I have read several of the threads here on this forum about plug torque I read that the earlier Pre-PI heads have the short thread count and someone else suggested that the later 2 valve PI heads have more threads, and the 3 valve heads have the long thread count. What is the real deal here???
 
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Old 11-06-2011, 05:50 AM
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I have a list of links to perhaps 20 threads about plug installation which I could post here for you--maybe you've read most of them already though.

At any rate generally the heads with 4 threads per hole should be torqued to about 20 ft/lbs with a nickel based anti-seize being used. 8 threads per hole seem to work just fine with this same torque while the issue of anti-seize being more a matter of personal perference. Of course these settings assume you'd be using Motor Craft or Auto Lite plugs.

Perhaps compounding some of the confusing information is that posted on the Blownsparkplugs.com site where they claim to have consistently run plugs up to 90 ft/lbs without failing.

Seems torque at 20-21 ft/lbs is the most common practice. The list of links is available if you'd like to read more.
 
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Old 11-06-2011, 08:16 AM
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I replaced mine at 65K miles (waste of time and money because they looked like new) with Auto-Lite and torqued to 14 ft lbs dry. I replaced my boots at 109K in July and checked the torque and everything was fine, I plan on replacing them at 165K. I have 117K on it now

Denny
 
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Old 11-06-2011, 09:48 AM
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Its good to at least check 'em at 50K-----a bit of work but worth it especially if they need replaced. The biggest problem is leaving plugs in too long where they gall to the head and make a mess there.

The boots can be a source of lots of problems so checking, re-lubing them and replacing if necessary just keeps the reliability high and trouble free.
 
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Old 11-06-2011, 10:04 AM
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Thanks JWA and rvpuller for the torque information , but what I am really looking for is the thread count in the 2001 PI head. Does the 2001 PI head have more threads than the earlier (1999) non- PI head, or is the thread count the same? Or perhaps a better question would be is the thread count for all the 2 valve heads the same and require the same care for plug removal, and installation?
 
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Old 11-06-2011, 12:34 PM
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I think the thread count was changed in 02. The biggest problem with is Ford doesn't use a compression ring and people not familiar with the tapered seat over tighten them and cause the problems. On a GM you torque the plug and then turn is 30' to crush the ring, if you do that to a Ford you will pull the threads.

Denny
 
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Old 11-07-2011, 07:40 AM
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Late November 2002, they went to the long-thread heads. I have no data corresponding to when in the MODEL year they switched though. Build dates around November 2002, it seems:

December 1996 - 4.6L 4V alignment feature added
February 1997 - 4.6L 2V head alignment feature added
September 2000 - WEP (Windsor Engine Plant) 2V head alignment feature modified (4.6/5.4/6.8)
November 2002 - WEP introduced long thread heads on 2V (all)
May 2003 - REP (Romeo Engine Plant) introduced long-thread heads on 4V 4.6 and 5.4
November 2003 - REP introduced long-thread heads on 2V and modified alignment feature

In 1999, and 2001, an interim fix was done for a cross-threading issue.
Original process:

Step 1 - Zero torque spark plug (air tool)
Step 2 - Torque to 16-20Nm final torque (DC Run down), monitor at 6-12Nm, and final torque must be reached within 0-360 degrees.

New process (addressed the possibility of applying installation torque for more than 25 degrees of rotation)
Step 1 - Zero torque spark plug (air tool)
Step 2 - Torque to 16-20Nm final torque (DC Run down) start monitor at 6-12Nm, and final torque must be reached within 3-25 degrees.

Another action to address cross-threading was the addition of an alignment feature to lead the plug into the hole.
 
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Old 11-07-2011, 09:49 AM
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And they switched to 3 valves in 05??

So the best PI heads would be late 2003 - 04?
 
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Old 11-07-2011, 10:26 AM
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That's correct.

The F-series went 3-valve in 2005. The 2005 Excursion was still a 2-valve, and the E-series has never gotten the 3-valve.

I would still inspect the heads to make sure they are long-thread before buying them.
 
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Old 11-08-2011, 01:25 PM
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It bears repeating that MOST early 2V have not had any plug spitting problems. And many of us are quite convinced that the most common root cause is improper torquing (ie, operator error), NOT the smaller number of threads. Others have independenty tested the strength of the threads and also found it takes a LOT of torque to destroy them. Like 90+ or 4X+ of the spec.
But the pain of ruining a head makes people very vocal about the situation.

More threads require will require more force to destroy, but they are still routinely destroyed. I've fixed stripped plug holes that had over an inch of threads...

If yours are damaged and need replacing, compare the price of a later set of PI heads to the price of just inserting Time-Serts into yours. If you pull the heads, it is a casual afternoon's job to insert all 10 cylinders and make it really, really hard to strip again.
 
 
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