04 Heads Spark Plug Threads Debate

[BurnTire]

Well we were having a heated debate on the 04 cobra head thread count for the spark plugs on a little site in Phoenix.

Well it appears in late 03 the 04 production line went to 9 threads.
I know this issue has been debated to death, but some 04's have 9 threads.

Photo evidence.

http://www.highperformancestangs.com/forums/showpost.php?p=11949&postcount=84


The Hole Debate if you care to read it.

http://www.highperformancestangs.com/forums/forumdisplay.php?f=19

 

[evans03c]

I did see another thread on here where someone said that 04's built up until Jan 04 had 4 threads and then went to 9.
The Jan 05 head #'s are 2C5Z-6049-BAB and 2C5Z-6049-CAB. Neither matches the number in the casting so they can't be new heads. Maybe it's true? Any chance that head has had the threads only replaced?

 

[BurnTire]

I did see another thread on here where someone said that 04's built up until Jan 04 had 4 threads and then went to 9.
The Jan 05 head #'s are 2C5Z-6049-BAB and 2C5Z-6049-CAB. Neither matches the number in the casting so they can't be new heads. Maybe it's true? Any chance that head has had the threads only replaced?

No those head were taken off of an 04 cobra that was purchased new.
A local shop here has borascoped six 04 cobra heads in the last 24 hours and they all had nine threads.

 

[Tank5879]

I did see another thread on here where someone said that 04's built up until Jan 04 had 4 threads and then went to 9.
The Jan 05 head #'s are 2C5Z-6049-BAB and 2C5Z-6049-CAB. Neither matches the number in the casting so they can't be new heads. Maybe it's true? Any chance that head has had the threads only replaced?

Ford stamps engineering numbers on parts, which are different than service numbers that you would find at your ford dealer.....that being said somethimes they are similar, and contain the same base number and close prefixes and suffixes....

 

[Tank5879]

I just logged on to HVBOM (Historical vehicle bill of materials) on the FMC site, and ran my VIN and dicovered that my car was built with the same heads as this thread is discussing...very interesting....it had that same number (anyone that hass access do limit to base 6049 and then click on COMP and it will break down the list and scroll down to 6049 in the list and do comp again and it will give you that rf number) RF.2C5E-6C064-DB....my car was built 12/03...this is very interesting news seeing that the popular thought was that all 03s and 04s had the 4 thread heads.....

 

[BurnTire]

The number of turns head thread Test

Well I came up with the The number of turns head thread Test.

Dan at Performance Solution in Phoenix tested out the theory for me.
Dan also adamantly stated the 04's have 9 threads and he was always right.

Basically there is a seat in the head for the wider portion of the plugs just above the threads to stop on. This seat, notch, ledge, whatever you want to call it is in the same location in the 03/04 heads. What is different is the 03 head threads start at the bottom of the head and go up 4 threads then there is space between there and the seat.

The 04 heads threads start at the same spot, but go up 9 threads much closer to the seat.

So when you screw a plug in your are using the bottom 4 threads of the plug on an 03 head and the bottom 9 plug threads on an 04.
Most plugs have 10-11 threads.

So this is how to find out how many threads your head has.
Make full 360 degree turns on the plug

4-4.5 turns to remove or seat the plug on a 4 thread head

8-8.5 turns to remove or seat the plug on a 9 thread head

 

[HISSMAN]

I got burned on this one the first time I changed my plugs. I noticed that I was turning the plugs about 8 complete turns to get them hand tight, then another half turn or so to get them to the proper torque spec. Everyone said I was crazy. Who is laughing now.

-Jeff

 

[BurnTire]

I thought all 04's had 4 threads and was wrong, but now we have the truth on the issue, pictures and a method to check the thread count.

 

[RAZRS EDGE]

I got burned on this one the first time I changed my plugs. I noticed that I was turning the plugs about 8 complete turns to get them hand tight, then another half turn or so to get them to the proper torque spec. Everyone said I was crazy. Who is laughing now.

-Jeff

+1!!!

 

[BWH2003]

Here is a good thread to reference the old belief. Also I was laughing at CobraBob when he bet the guy a beer. Its about five posts down or so....

http://www.svtperformance.com/forums/showthread.php?t=323101&highlight=spark+plug+threads

 

[BLK03SVT10TH]

I'm pretty sure my late production 2003 10th Anniversary and my 2004 Mystichrome both take 8-9 rotations to get the plug out, but according to other information in those other threads, it doesn't necessarily mean I've got 9 thread heads. Correct?

 

[HISSMAN]

I'm pretty sure my late production 2003 10th Anniversary and my 2004 Mystichrome both take 8-9 rotations to get the plug out, but according to other information in those other threads, it doesn't necessarily mean I've got 9 thread heads. Correct?

Honestly though I am still up in the air about it. I will figure it out somehow though.

 

[BLK03SVT10TH]

Honestly though I am still up in the air about it. I will figure it out somehow though.

It would really depend if the threads start at the top of the hole near the seat, or at the bottom of the hole near the chamber. If they start at the top of the hole, there could be 4 or 9 or 20 threads and the spark plug would still screw in the number of threads on the spark plug.

Now if the threads are recessed below the spark plug seat, you still can't actually tell by counting the number of rotations how many physical threads there are, but knowing that the depth of the hole is limited and so are the number of threads on the spark plug, you could make a logical assumption that there are only 4 threads there if the spark plug takes 4 rotations to seat.

But without pics, its still a crapshoot.

 

[BurnTire]

Photos
http://www.highperformancestangs.com/forums/showpost.php?p=11949&postcount=84

The 4 thread heads have the same seat, but only have 4 threads from the combustion chamber up.

Number of turns is how you tell. If someone says other wise they have never had a set of heads 03 and 04 in their hands.

Basically there is a seat in the head for the wider portion of the plugs just above the threads to stop on. This seat, notch, ledge, whatever you want to call it is in the same location in the 03/04 heads. What is different is the 03 head threads start at the bottom of the head and go up 4 threads then there is space between there and the seat.

The 04 heads threads start at the same spot, but go up 9 threads much closer to the seat.

So when you screw a plug in your are using the bottom 4 threads of the plug on an 03 head and the bottom 9 plug threads on an 04.
Most plugs have 10-11 threads.

So this is how to find out how many threads your head has.
Make full 360 degree turns on the plug

4-4.5 turns to remove or seat the plug on a 4 thread head

8-8.5 turns to remove or seat the plug on a 9 thread head

This isn't a guess. This was tested on a set of 03 and 04 heads that were taken off of their respective cars.

I personally did the 04 head test and Dan at Performance Solution in Phoenix did the 03 set.

This is the outright facts. If anyone says other wise we can take a video.

 

[BurnTire]

I'm pretty sure my late production 2003 10th Anniversary and my 2004 Mystichrome both take 8-9 rotations to get the plug out, but according to other information in those other threads, it doesn't necessarily mean I've got 9 thread heads. Correct?

Those other threads are wrong.

You have the correct information now.

 

[BurnTire]

I'm pretty sure my late production 2003 10th Anniversary and my 2004 Mystichrome both take 8-9 rotations to get the plug out, but according to other information in those other threads, it doesn't necessarily mean I've got 9 thread heads. Correct?

It appears that sometime in Nov of 03 the cars went form 4 to 9 threads.

The easy way to tell is to use the number of turns test above or if you have a borascope you can take a look inside.