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I was wondering where to find the date code on engine block and cylinder head.

I found 3-row codes respectively on the engine and cylinder head.

On the block the 3-row code is to be found in the area between the starter and the motor mount.

On the cylinder head the 3-row code is found on top of the integral exhaust manifold, just before the external exhaust flange.

In both cases, in the first row I found was a 4-digit number followed by a letter.

From what I understand, the 4-digits represent a 3-digit day of the year followed by a 1-digit for the year.

I applied that key to my engine and it appears that my cylinder head and engine were cast just one day apart and just over two weeks after we ordered our vehicle.

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Engine block number location (rear of engine, driver side):

Engine SN location.jpg

There are two plates in that area, here are mine:

Engine 1.jpg

05184841AI - casting number
1783133712 - possible interpretation: 178th day of 2013 (June 27, 2013)

Engine 2.jpg


178: Day of year: June 27
3: Year: 2013
D: D line, Trenton South
1504:Serial in the day
0: 0
136: 3.6 JK (Wrangler)
000: ?
112212: cylinder bores? (cylinters 1-6)
3223: crank bore? (bearings 1-4)

Example of left head plate:

Left head 2.jpg

Interpretation of my right-side head plate:


177: Day of year: June 26
3: Year: 2013
?: Line
0226: serial # that day
0: 0
014: Part type: 3.6 right base, old ECT
000: ?

See to decode yours
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