Below each spark plug on the engine block is this symbol. It looks like a hand painted upside down "P". I am guessing some sort of manufacturing mark. But is it from original factory, or is this from some rebuild shop?

 

Hand-painted A-B-C-D-E-F under each cylinder, the letter indicates what size piston fits the cylinder. Those look like a lower case D. All 6 the same?
As I understand it "C" is standard size, A-B are slightly undersize and D-E-F are slightly oversize.

 

Yep. All six are the same.
Does everyone's engine have these sort of markings?

 

I've never seen that on either of my XJs or on anybody's I've ever looked under the hood of... then again mine is pretty greasy so maybe it's covered...

 

Do you have a late '96? I have an early '96 and have several different letter sizes.
I believe the Kenosha 4.0 block line was replaced in '96 as the old machinery was worn out, engines built after the replacement may not have had the variances engines built prior did.
I'd be interested in leaning whether those with 97+ engines have the same letters or if they were done away with.

 

Whew! I thought I might have had a jy motor in mine lol, I'll have to check again and see which ones I have,

 

Whew! And here I thought I might have had a JY motor lol I'll have to check what mine are again

 

Not sure of the build date or location. I just sort of thought all XJ's came from Toledo. So where were the XJ's made? Engines made?

I noticed this year Chrysler built the 5 millionth Grand at North Jefferson Detroit. But that was three different bodies of 20 years.

 

No markings on my '00 XJ block.

 

Just googled and this what cane up: 1984–2001 (USA)
1984–2005 (China)
1987–2001 (Venezuela)
1996–2000 (Argentina)
1992–1997 (Egypt)
Assembly Toledo, Ohio, United States
Beijing, China (Beijing Benz)
Valencia, Venezuela
Ferreyra, Argentina
Cairo, Egypt (AAV)

 

No markings on my '98. I have never heard of the piston sizes being different amongst themselves...is that true?

 

Yes, quite a few of those blocks were built with different piston sizes. We're talking differences of 0.001", not huge tolerances. They'd look at the letters on the block and grab pistons out of the box with matching letter sizes.
I think that went away after the '96 re-tool, but not entirely positive.

 

The XJ's were built in Ohio, the engines, all 5 million of them, came from the Kenosha (WI) engine plant. (I have relatives who worked there)

 

My 2001 doesn't have any markings.

 

my 96 has the markings, and different lettering for each cylinder