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cylinder scratch

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Hi, everyone

I discovered a scratch in the cylinder of my engine

I can feel it slightly by running my fingernail over it.

I have attached a photo.

Do you think this engine will work?

Attached Files

It seems to me quite deep. I personally would not use it in such shape...

What kind of problems would i have if i run it?

Blow by gases, lower compression pressure, crank case back pressure, uneven power stroke by cylinders...

I specify that this was done during the break-in with a flex hone tool, the drill stopped suddenly during the movement.

During the break-in period, the cylinder will wear and the depth of the scratch should decrease.

What do you think ?

Usually cylinder wall wear is about 0.01-0.02 mm after breaking in. If the scratch is deeper than that it's not going to work properly

Not so much "a" scratch, but a bunch of scratches with that the deepest one. I assume you were running the engine without an air filter, as that's the usual reason for that sort of damage. What are the other cylinders like?

It isn't going to "go away" from bore wear as the engine is run - remember, the cross-hatching can last tens of thousands of miles (I've had instances of them still being visible after more than a hundred thousand) and they're MUCH shallower than those scratches. The lack of wear is a good thing as that removed material has to go somewhere, and opens up the ring gap.

Depending on what the engine is being used, it may not be that critical, or it may lead to early piston failure - a low rev'ing engine that's lightly stressed should be OK, but a high compression engine, especially if used with forced induction, will have leakage past the rings that in a worse case could cause the hot gases to scour the side of the piston and melt a channel down the side. Either way, there will be a small loss of cylinder pressure and increased blow-by.

Personally, I'd be looking at a rebore unless I HAD to have it running for something, and then I'd run it in the expectation of reboring ASAP.

The biggest risk with a scratch like that, particularly during break in is it will catch on the rings, and risk snagging/damaging your ring pack.

The fact that is freshly honed and receiving new rings is its highest chance for causing issues.

thank you very much for all your advice, is there a test that I can do while the engine is disassembled to check the tightness of the cylinder?

Can't think of one off hand, sorry.

When assembling an engine it's very important to get it done properly if the goal is to get it up and running reliably for a long time -even if it seems to be taking extra time and money. There some fundamental things that have to be done in order to achieve reliability and good performance. So it would be wise to build it right from the first time rather than face a problem later on and have to come back for revisiting it spending even more time and money on something that could have been prevented... I'm sure we are smart enough not to create a time bomb for ourselves if the engine is planned to be used for a long time...

i asked earlier wha tthe other cylinders were like, but I'll add to that "what are the pistons like"?

This engine is a 5.3 lm7 v8. there is another similar scratch on cylinder number 6 which is smaller and shallower. all other cylinders except cylinders 6 and 4 are correct. I cleaned all the pistons, no scratches, I did not detect any anomaly. when i took the intake apart there was a lot of dirt inside so i guess it may have been used without a filter as mentioned earlier in the discussion. on my island there is only one engine machining company and they only support engines with inline cylinders. this project is my first rebuild with slight modifications to the bearing clearances (+0.0005), my goal was to make it work with 5psi of boost and 5800 rpm max. it is a street soft project which aimed to test this type of engine (do my experience). It's not a long-term project, if it lasts 30,000 kilometers, with a little oil consumption and without a huge loss of compression, it's good for me.

Just rehone it for a couple seconds.

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