To determine the Julian date of your LS2, there's a sticker on the back side of the left cylinder head. There's also a sticker above the oil pan rail on the left front side of the engine block, although this one is more difficult to read. A typical Corvette engine number might be
10ZJBK042750836.

10 stands for engine
ZJB is the engine suffix
K stands for St. Catharines
04 is the model year
275 is the Julian date
0836 is the engine serial number

This would mean that this engine was built on the 275th day of 2004.


Mark

 

ok so what exactly is a jullian date ?

 

The Julian date is the day of the year the engine was built. For example 001 is Jan 1, 002 is Jan 2, and so on. With the concern of the crank pulley bolt loosening and the possiblitiy of the pulley coming off, any engine that was assembled before Julian date 341 is a candidate for this to occor. After Julian date 341, the engine has the diamond encrusted washer installed at the factory.

Mark

 

The number of days since noon on January 1, -4712, i.e., January 1, 4713 BC (Seidelmann 1992). It was proposed by J. J. Scaliger in 1583, so the name for this system derived from Julius Scaliger, not Julius Caesar. Scaliger defined Day One was as a day when three calendrical cycles converged. The first cycle was the 28 year period over which the Julian calendar repeats days of the week (the so-called solar number). After 28 years, all the dates fall on the same days of the week, so one need only buy 28 calendars. (Note that since the Gregorian calendar was adopted the calendar now takes 400 years to repeat.) The second was the 19 year golden number cycle over which phases of the moon almost land on the same dates of the year. The third cycle was the 15 year ancient Roman tax cycle of Emperor Constantine (the so-called indiction). Scaliger picked January 1, 4713 BC on the Julian calendar as Day One. The three cycles coincide every 7980 years (Tøndering).

 

Is the 341 date still the cutoff since the new list shows a VIN as the cutoff? The reason I ask is mine is over the VIN list but under the Julian date according to this information. My number is 10ZJB-K043360925 with a VIN of 5111025. The BG plant said mine was okay but now I have no idea.

 

Wow
Thats alot of info
Thanks

 

Actually, you're under the vin breakpoint of 55111039 since you said your vin is 5111025.

Mark

 

Wow, why don't they just call it the "date of manufacturer"? Sorry - I'm a simple kind of guy :o

Actually, I'm not posting to bust anyones nuts - just thanks for posting good information

 

The VIN is 55111250. I typed the wrong number in the first post.

 

there seems to be some misconceptions about Julian dates.
the 3 digit numbers that most people consider to
be "julian" dates are in fact "Day of Year" indicators which have no
relationship to true Julian date codes used by manufacturers.
rather than give a lengthy explanation, I would suggest a quick
peek at the following link that will allow you to convert true Julian
dates:
http://aa.usno.navy.mil/data/docs/JulianDate.html
October 1st of 2004 is Julian date 2453279, and many manufacturers
simply use the last 3 digits of the julian dates for some stamps.
January 1st 2005 is Julian date 2453371 so if you found a stamp of
"371" it may refer to Jan 1st 2005. since some years have more days
than others, a simple 3 digit "day of year" code is not very valuable
unless the year is also indicated. true Julian dates have a fixed starting
epoch (January 1, 4713 BC) and are therefore useful as a perpetual date code system.

the true Julian date of "341" equals December 2nd, 2004.
the Day Of Year 341 for 2004 equals December 6.
since the previous post did not make it clear which "julian" date system
was being used, it is ambiguous.

if you found a stamp of "302" that could mean true Julian Oct-24-2004
or DOY Oct-28 for 2004. it all depends which system is used.

to further complicate things, it is merely coincidence that the DOY
and Julian dates are so close this year. 300 to 341 or so, corresponding
to October-December.

in summary there is no such thing as a 3 digit Julian date, and
the day-of-year stamps are only useful when the year is also indicated,
which it is on the engine sticker.

 

thats a good question and the answer is that the 3-digit codes
that are incorrectly referred to as "julian dates" are actually
the day-of-year codes and are basically useless from a tracking
standpoint unless the year is also indicated. (see my post above).
date "341" doesnt tell us much, but a true Julian date of 2453371 for
example does. (Jan 1, 2005)

 

Actually, as I explained originally, the year is indicated by the "04" in the example I gave. The information I used came directly from a GM powertrain engineer.

Mark

 

Damn, I'm impressed! (This is NOT meant in a sarcastic manner)

Thanks for the education

 

Well, the education isn't over yet. There is a big, big difference between the Julian Calendar, and the Julian Date.

The Julian Calendar was, in fact, brought to us by Julius Caesar, and is what we use today in slightly modified form thanks to Pope Gregory XIII (and so does Chevrolet on it's engine blocks). So now we call it the "Gregorian Calendar." Here's a quick summary:

"In the year 46 BC, the Greek Sosigenes convinced Julius Caesar to reform the Roman calendar to a more manageable form. At this time, Julius also changed the number of days in the months to achieve a 365 day year.... The Julian calendar consisted of cycles of three 365-day years followed by a 366-day leap year. Around 9 BC, it was found that the priests in charge of computing the calendar had been adding leap years every three years instead of the four decreed by Caesar ..."

and

"the Gregorian calendar, now used universally for civil purposes, and the Julian calendar, its predecessor in the western world... The Julian calendar has a leap year every fourth year, while the Gregorian calendar has a leap year every fourth year except century years not exactly divisible by 400... the changeover from the Julian calendar to the Gregorian calendar occurred in October of 1582, according to the scheme instituted by Pope Gregory XIII... The changeover to the Gregorian calendar system occurred as described above only in Roman Catholic countries, however. Adoption of the Gregorian calendar in the rest of the world progressed slowly. For example, for England and its colonies, the change did not occur until September 1752..."

Now, the Julian Date is a completely different animal, as in:

"The number of days since noon on... January 1, 4713 BC. It was proposed by J. J. Scaliger in 1583, so the name for this system derived from Julius Scaliger, not Julius Caesar."

What's the big deal?

Well, that engine block above was built in 2004, on the 275 day of the 365 day year (there's that pesky 365 again). Oh, that would be October 2, 2004. That's all it is, it's not the Julian "Date."

The Julian "Date" for that day, per Mr. Julian Scaliger, would be:

2,453,280 -- give or take a half.

So as you can see, day 275 of 2004 is quite different from day 2,453,280.

And 2,453,280 appears no where on the engine block.

Try it yourself, courtesy of your tax dollars at work:

http://aa.usno.navy.mil/data/docs/JulianDate.html