Curious markings on engine block.

Picked up a JY motor to eventually rebuild for our high mileage XJ. The motor is out of a 95 the date code verifies this, weird thing was markings in white pen on the side of the block.
About the middle of the block.
D C D C C C

They have been there for a long time and are underneath some of the brackets. I never seen anything like this curious if anyone has and what they mean.

piston to cylinder bore matching. all 4.0 have this.

well, I tried to hot link the chart, but it didnt work

Ok cool. I've not seen one before. Either painted over or too dirty I guess.

Once I knew what there represented I could do some more searching here and found this.

MJR said:

CYLINDER BORE SIZE PISTON LETTER SIZE
98.438 - 98.448 mm (3.8755 - 3.8759 in.) A
98.448 - 98.458 mm (3.8759 - 3.8763 in.) B
98.458 - 98.468 mm (3.8763 - 3.8767 in.) C
98.468 - 98.478 mm (3.8767 - 3.8771 in.) D
98.478 - 98.488 mm (3.8771 - 3.8775 in.) E
98.488 - 98.498 mm (3.8775 - 3.8779 in.) F

Click to expand...

http://www.naxja.org/forum/showthread.php?t=1021920

"direct fit" components.
Lots of manuf's do that, it's a "lean manufacturing" process.
It all depends on where the casting's clean up.
Some use color codes.

Makes it a bit hard to give the bores a hone and re ring I imagine

Bores would just be oversized to a "off the shelf" piston/ring size I.E. .020,.030 etc.
You'll see that on oem crankshaft bearings often.
Could be many types of markings such as letters, numbers, notches, dots, colors.
Honda and Suzuki engines come to mind, but that's another story.

Ewenm said:

Makes it a bit hard to give the bores a hone and re ring I imagine

Click to expand...

Sorry, misread this post, i'm a dummy.
Yes I would agree with you, because you'll have to use the chart to get the ring set's.
The cylinders are always to far out of round to do that every time that procedure seems to be a option for me.

So if the original pistons were to be re-ringed it would be a hassle to match up the correct sizes?

Honestly I don't want to rebuild it really, just clean it up and run it when the time comes, rather rebuild the block I know the history of in the jeep now. The doubt in my mind is if we should redo the bearings or leave them. Was planning on new head gasket (always do this with especially unknown older motors thanks to bad experiences with Japaneses cut out motors), and new oil pump just because it's easy to get at now. Then start thinking of the others things it easy to get to now, easy to get lost.
But I know I'll start losing ground if I let myself get too involved. If I knew for sure what it cost to take the block into a machine shop I'd probably be tempted, last time had a blocked machined was in the late 90s and I did get carried away rebuilding that (in retrospect POS) car.

Back on topic I read the size variations were caused by a worn out block boring machine.
C should be standard, D oversize.
And this practice of writing the sizes on the block went away 1997-98 with a new engine line.

I've never noticed these mark on other jeeps I've worked on, too dirty maybe.

Ewenm said:

Makes it a bit hard to give the bores a hone and re ring I imagine

Click to expand...

No.

There is only a .0024" size difference between A piston and F piston.

The ring end gap is not affected, so one ring size fits all.

Digger87xj said:

No.

There is only a .0024" size difference between A piston and F piston.

The ring end gap is not affected, so one ring size fits all.

Click to expand...

I agree w/ this, to a point, I'm sure you'll have to file your own gaps in most cases.
However the inline 4.0 YJ,ZJ XJ engine has a slightly larger than one and a half thousandths of a inch piston to wall clearance(.0017 from what i'm reading).
Never had luck getting that number on a used engine, not to mention side clearance.
Anyhow that's off topic.

Worn out machine thing is....
OEM's try to use as little of everything as possible, including material, cutting and grinding tools, utilities, labor hours. Less is more as far as there concerned.
There still doing it, but there is better equipment to do it with.

So don't worry about the stupid frickin' letters, they are not important.
Smiley face.