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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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#35 ·
Re: 2004 Deville Determining Headbolt Thread Pitch

The information in this thread is only for 2004 year-model northstars ... all earlier years are the less-coarse thread pitch and all later years have the coarse thread pitch

if you are looking for different information about your 2003 DTS please be specific as to what information you are looking for
 
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