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Determining Headbolt Thread Pitch

32K views 37 replies 12 participants last post by  MoistCabbage 
#1 · (Edited)
I believe I may have come up with a way to determine if a 2004 Northstar has the 1.5mm thread pitch that the 2000-2003's have or the 2.00mm thread pitch that the 2005's have. Below is what came out of the parts catalog courtesy of Chris aka RippyPartsDept...




From this we can determine that 2004 N*'s with the following engine ID's have the M11x1.5 threads like the 00-03's have.

JBA
JCA
LBA
LCA
JKB


We can also determine the following 2004 engine ID's have the new and improved M11x2.0 threads like the 05's have.

JBB
JBC
JKA
JMA
JMB
JPA
JPB
LBB
LCB


The way I read the parts catalog... it looks like all LD8's have the 2.0mm threads and the L37's could have either the 1.5mm or the 2.0mm threads. (The LD8 came in the Base and DHS models the L37 came in the DTS model.)


Just to make sure... you can determine your engine ID by looking at the sticker attached to the passenger side of the rear rocker cover... labeled #1 in the picture below.


As you can see in the picture below my 04 Deville has an Eng ID "JMB" which would indicate that I have the 2.00mm thread pitch. :cloud9:

The same sticker also indicates the engine build date... mine being 05/06/04.




Below is a little more info about the thread pitch change that came out of the 2004 FSM...

"The thread pitch on the M11 cylinder head bolts and the engine block cylinder head bolt holes has been revised for MY2004."

"The MY2003 and earlier cylinder head bolts have a pitch of 1.5 mm and the length of the threads are about 48 mm (1.890 in) long."

"New for MY2004 the cylinder head bolts have a pitch of 2.0 mm and the length of the threads are about 67 mm (2.638 in) long."
 
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#4 ·
Re: 2004 Deville Determining Headbolt Thread Pitch

awesome ... thanks for doing the heavy lifting here

i knew there was enough info out there to figure this out as long as someone was able to put all the pieces of the puzzle together

:cheers:
I couldn't have solved it without the critical piece of the puzzle that you came up with Chris.:thumbsup:

If I ever find myself shopping for another 2004 I will definitely print out post#1 to take with me.
 
#5 ·
Re: 2004 Deville Determining Headbolt Thread Pitch

So with the new thread pitch there have been little to no pulled head bolts? This is great information if this is true..So in 2005 they all had the new thread pitch im assuming? So in everyones opinion what anti freeze is best to help prevent any head "gasket' issues..I know these cars came with Dex Cool but I heard that it is not ideal for the head gaskets.. i know thats still a debate amongst certain people..Lol...If I should choose to run the conventional green stuff and change it every year...should I be ok?
 
#6 ·
Re: 2004 Deville Determining Headbolt Thread Pitch

as long as you change it when it needs to be changed you shouldn't run into any problems with either

i would stick with dexcool because that's what anyone working on the car would expect to be in there.... just in case

----------

also, no pulled bolts with the coarse threat pitch design ... but as i said in your thread just now there have been some loose bolts causing gasket failure ... but very very few
 
#7 ·
Re: 2004 Deville Determining Headbolt Thread Pitch

Hate to revive an old thread, but I was looking at the sticker on the engine of my 2000 Deville and it is a "JMA". And if the OP's theory is correct that would mean it had the new longer bolts that were not available until a few years after it was made..Now im not saying that his theory is wrong..not at all..But the purpose of my post is to say that if I do indeed have the newer design then it aint much better than the old one...My head head gaskets went at 65,000 miles on this car..Is it possible that the designation "Jma" meant something different in 2000? After all I dont believe the newer bolts were even available, but if this car by some chance did have them then they aint worth a damn either..I had a few pulled threads on my head bolts...
 
#9 ·
Re: 2004 Deville Determining Headbolt Thread Pitch

I was looking at the sticker on the engine of my 2000 Deville and it is a "JMA". And if the OP's theory is correct that would mean it had the new longer bolts
Your 2000 never had the M11x2.0 threads.

If you go back and look at the title of this thread "2004 Deville Determining Headbolt Thread Pitch" and the actual content of post #1... you will see this entire thread and the engine ID codes only apply to the 2004 model year Deville.

We can also determine the following 2004 engine ID's have the new and improved M11x2.0 threads like the 05's have.

JBB
JBC
JKA
JMA
JMB
JPA
JPB
LBB
LCB
 
#13 ·
Re: 2004 Deville Determining Headbolt Thread Pitch

Ok Im sorry, I guess I didn't totally understand the post the first time I read it. So if these engines were out of a car and we didn't know what year they came from I guess we cant go by the "jma" or any of the other three letter codes soley..We would need to know the engine build date..You see the picture of your engine code has the date on it...mine does not for some reason..So 2004 would be the absolute soonest that the newer style bolts were available? In 2005 they all came with them? Ok cool..thanks for all your info guys...Have a safe and happy holiday!
 
G
#17 ·
Re: 2004 Deville Determining Headbolt Thread Pitch

OMG i feel so relieved now great info i just came across the thread and just went out side at 4AM :bouncy: to check the label and my 04 DTS is a JKA knew she was a winner day i got her steal for $5000 grand guy took $1000 off for a cracked grill and broken rear regulator i forgot to look at when she was built but im happy now since im fixing all the little things little by little last thing i wanted to know was it kinda be for noting considering the earlier northstars are bound to go sooner or later thanks guys :cool2:
 
#18 ·
Re: 2004 Deville Determining Headbolt Thread Pitch

OMG i feel so relieved now great info i just came across the thread and just went out side at 4AM :bouncy: to check the label and my 04 DTS is a JKA
Glad to hear that you where able to determine you have the improved 2mm thread pitch.

What's your engine build date? It's the date at the bottom of the sticker as pictured below.

 
#20 ·
Re: 2004 Deville Determining Headbolt Thread Pitch

Build date is 8/8/03 mmmh 03 should i be concerned? it says JKA and there werent no earlier JKA's built on the list what u guys think do i got the 2mm's?
Very interesting...
That's an early build date on an L37 (04 DTS) engine. It must be a very small number of 04 DTS's that came with the smaller 1.5mm threads. According to the parts catalog you have the larger 2mm threads.
 
G
#21 ·
Re: 2004 Deville Determining Headbolt Thread Pitch

Hey guys HAPPY NEW YEAR anyway figured i reopen this thread okay so now we have some proof on the deville engine ID's about what thread pitch they have but what about the sevilles? 98 to 04 SLS or 98 to 03 for STS model? pre 04 has the 1.5 threads but what about a 04 SLS? and a 03 STS is also possable i think as i have a 04 DTS with a L37 built in august 03 with ID number JKA which indicates the 2.0 threads?
 
#22 ·
Re: 2004 Deville Determining Headbolt Thread Pitch

Hey guys HAPPY NEW YEAR anyway figured i reopen this thread okay so now we have some proof on the deville engine ID's about what thread pitch they have but what about the sevilles? 98 to 04 SLS or 98 to 03 for STS model? pre 04 has the 1.5 threads but what about a 04 SLS? and a 03 STS is also possable i think as i have a 04 DTS with a L37 built in august 03 with ID number JKA which indicates the 2.0 threads?
Great question! Anyone know if the 2004 SLS has the same engine codes?
 
#24 ·
Re: 2004 Deville Determining Headbolt Thread Pitch

Do these engine IDs apply to the 2006 DTS also? I understand the statements that assign L37/LD8 to 2004's but would like to be absolutely certain before I buy this 2006 DTS. Just finished a $2500 time-sert head gasket job on my 97 deville Northstar.
 
#28 ·
Re: 2004 Deville Determining Headbolt Thread Pitch

The 2004 model year ran from about late July 2003 to early June 2004. The engine could have been built at any time before or during that run - the engine build and ID number is on the end of the right (rear) cam cover. Many of the parts for your car's body were probably stamped out in earlier 2003 - for a "2004" car. Same for the engine parts and even the carpets.

The final build date (within 30 days) for the car is on the driver's door sticker.

Changes - in every part of the car - are (computer programmed and) made on the fly. A car built on 08/30/03 might have an entirely different widget control sensor from one that rolled off the line on 09/01/03........... and maybe different for one that was built in 05/2004 - toward the end of the 2004 year.
 
#29 ·
Re: 2004 Deville Determining Headbolt Thread Pitch

Thanks! Yes i was aware that although parts for any given model year could have been made at any time including the previous year(s) for that model year. I was under the belief that the engines made specifically after a certain date in 04 have the upgrade. So, not only for the model year 04 but also manufactured in 04 as well.
 
#31 ·
Re: 2004 Deville Determining Headbolt Thread Pitch

not for all years... just ones mfg'd after the break in 2004

if you have a 2004 the info in this thread can tell you if you have the final updated design (coarse thread) bolts

if you have 2003 or earlier then you don't
if you have 2005 or later then you do

only for 2004 does this info apply to tell if you have the coarse thread bolts or not since 2004 was the year that the change was made

...

build date does not apply here
only model year (10th digit of the VIN)
 
#32 ·
Re: 2004 Deville Determining Headbolt Thread Pitch

Ok Thanks!..Because i am looking at a 2004 SLS that has an engine build date of 2003 (June) and i was thinking build date applied as well. But as long as i have model year and upgrade code indicating , I am better off. In this case , JMA on this particular car.
 
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