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Discussion Starter · #1 ·
The pistons in my engine have markings on them. Not numbers. Letters.

1 and 2 have what looks like a C, or an O marked on them.

3 and 4 have what looks like either a B, or an M.

Can anyone tell me what these mean ?
 

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Selador said:
The pistons in my engine have markings on them. Not numbers. Letters.

1 and 2 have what looks like a C, or an O marked on them.

3 and 4 have what looks like either a B, or an M.

Can anyone tell me what these mean ?
It's an acronym.

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The Motor Fairy stamps them on the pistons at night after an old fart starts an engine rebuild project.

Don't worry, it'll bring you good luck.

:)
 

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Discussion Starter · #3 ·
electricpuppyboy said:
It's an acronym.

Codgers
Otherwise
Build
Motors

The Motor Fairy stamps them on the pistons at night after an old fart starts an engine rebuild project.

Don't worry, it'll bring you good luck.

:)
You know what's really funny is that it actually does look like it is C on #1, O on #2, B on #3, and M on #4.

I just assumed that it was two Cs, or Os, and two Bs or Ms, because that made the most sense.
 

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I know the 2.6 has a direction arrow on the pistons.

As far as the other markings can't say for sure. Some manufacturers used to fit the individual pistons to the bores. There is a tolerance RANGE for everything. But if you are at the tight end it would be marked with one mark and a piston at the loose end would have a different mark. That way if the honing in the bores was a little loose you fit the bigger piston. GM did this for years. Maybe Jerry will check in on this.
 

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That's it. Maybe not an arrow but that is what Isuzu calls a cutout front mark. It should be on the front side of the engine for every piston.
You can see it on the #1 piston in this pic of my engine.


Do you have a factory manual? There are several real specific things about connecting rod, piston, and ring placement that is not in the aftermarket manuals. Things that will make a big difference in the long haul. Ring placement is a little different than the norm in these engines.
 

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Discussion Starter · #7 ·
squatch said:
That's it. Maybe not an arrow but that is what Isuzu calls a cutout front mark. It should be on the front side of the engine for every piston.
You can see it on the #1 piston in this pic of my engine.

Do you have a factory manual? There are several real specific things about connecting rod, piston, and ring placement that is not in the aftermarket manuals. Things that will make a big difference in the long haul. Ring placement is a little different than the norm in these engines.
Thank you.

Yup, that hole is in the same place on all 4 pistons.

I'm not doing a rebuild on the bottom end at this time. I am just finishing up a head swap. And I wondered what the letters on the pistons signified.
 

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Mine has similar stamps on the piston, 3-D's and 1-C, and corresponding stamps on the deck adjacent each bore. I assumed it identifies oversize bore and piston, C being .030 over and D .040 over. I've seen that coding used somewhere.

I just found this on another site:

"Not so much oversize, but the factory used that as a means of fitting pistons to a comparably sized bore to allow for differences in manufacturing tolerances. You have A,B,C,D pistons and A,B,C,D bores. You can also have E,F,G,H pistons and bores, which ARE oversize. They'd use this tolerance to salvage a block that might have been bored wrong.

Look on the block deck surface and see if the individual bores have a B, C, or D mark stamped on them."
 

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Discussion Starter · #9 ·
lucky guy said:
Look on the block deck surface and see if the individual bores have a B, C, or D mark stamped on them."
Too late for that now.

:wink: :D :D
 
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