Paint pen marking on 2.5 engine? - JeepForum.com
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post #1 of 7 Old 09-16-2019, 09:35 PM Thread Starter
Flint762
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Paint pen marking on 2.5 engine?

Hello,
I picked up a 95 2.5 engine that I am planning on rebuilding/ learning on. The person I got the engine from does not have any history as he bought the jeep and started swapping in a V8. On the right outside of the engine there are paint pen marks at each of the cylinders the letter D at #1 and the letter C at #2, 3 and 4. Do they have any meaning? my currant 92 engine does not have these markings. I have not been able to find any info when doing a search.
Thanks

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post #2 of 7 Old 09-17-2019, 05:32 AM
EABiker
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Just guessing....Someone could have done a compression test, and found that #1 was different than thee other 3.
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post #3 of 7 Old 09-17-2019, 06:18 AM
letitloose06
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Those paint pen markings are from the factory. When the engines were built, pistons were matched to each individual bore based on the size. The markings indicated what piston needed to be used in each bore.

Typically over the years they wear away or get covered up by grease or oil. I'm sure if you clean up the old engine you'll find similar paint pen markings.

These are for a 4.0, but the 2.5 was similar.

PISTON SIZE CHART

CYLINDER BORE SIZE PISTON LETTER SIZE
98.438 to 98.448 mm (3.8755 to 3.8759 in.) . . . . . . .A
98.448 to 98.458 mm (3.8759 to 3.8763 in.) . . . . . . .B
98.458 to 98.468 mm (3.8763 to 3.8767 in.) . . . . . . .C
98.468 to 98.478 mm (3.8767 to 3.8771 in.) . . . . . . .D
98.478 to 98.488 mm (3.8771 to 3.8775 in.) . . . . . . .E
98.488 to 98.498 mm (3.8775 to 3.8779 in.) . . . . . . .F
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post #4 of 7 Old 09-17-2019, 06:38 AM
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Quote:
Originally Posted by letitloose06 View Post
Those paint pen markings are from the factory. When the engines were built, pistons were matched to each individual bore based on the size. The markings indicated what piston needed to be used in each bore.

Typically over the years they wear away or get covered up by grease or oil. I'm sure if you clean up the old engine you'll find similar paint pen markings.

These are for a 4.0, but the 2.5 was similar.

PISTON SIZE CHART

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

I had the same marks on my block as well and had thought it must be a junkyard swap by the previous owner.

Thank you!
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post #5 of 7 Old 09-17-2019, 06:44 AM
wytetrash
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Quote:
Originally Posted by b00001 View Post
GREAT INFO!!!

I had the same marks on my block as well and had thought it must be a junkyard swap by the previous owner.

Thank you!
That is some really good information!

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post #6 of 7 Old 09-17-2019, 05:47 PM Thread Starter
Flint762
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Thanks. That is some great info. Not having any history on the engine that kind of info really helps. Mileage on the jeep when the engine was pulled was around 160,000 miles. This is going to be my first engine rebuild so I have lots to learn. Thanks again.
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post #7 of 7 Old 09-17-2019, 09:34 PM
Flyer58
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I have the letters stamped into the block near the top.
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