Nicks in Cylinder Walls

[Matt Wilson]

I'm at the point of checking all the machine work, parts dimensions, etc., for a 265 engine rebuild that I'm doing, and I discovered a few nicks on the walls of cylinders 3 and 4. There are two nicks in each cylinder. The smallest is roughly circular, and about 1/32 across and maybe a thousandth or so in depth (just my estimate by feel and looking under magnification). That one almost seems like a possible casting flaw that broke through when the cylinder was machined oversize.

 

The others are all between 1/16 and 3/32" in length and are at an angle to the cylinder, so not vertical like scratches one often sees due to ring end gap burrs or contaminants, but not quite lined up with the crosshatching either. I can catch my fingernail on one or two of those, and the others I can feel with my fingernail or fingertip, but not catch with my nail. I estimate the deepest ones are 0.002 - 0.004", although I could be off on that.

 

All of the nicks are separated from each other by a fair distance, and there doesn't seem to be any raised material next to them.  They are all between 1/2" and 1-1/2" from the top of the bore.

 

I plan to talk to my machinist about it and see what he says, but I wanted to get your opinions as well. From a performance standpoint, those are so tiny, they shouldn't matter at all in the sense of holding compression or letting oil get past, but I'm more concerned about whether they will shorten the life of the rings. 

 

Thanks,

 

Matt

[JBNeal]

A follow-up magna-flux check may be in order...

[Matt Wilson]

4 hours ago, JBNeal said:

A follow-up magna-flux check may be in order...

Good thought, thanks.  I'll talk to the machinist about this.

[Radarsonwheels]

I bet you could run it but it never hurts to get it right and the peace of mind you get from triple checking and cleaning everything is priceless.

[Matt Wilson]

On 12/29/2018 at 3:45 PM, Radarsonwheels said:

I bet you could run it but it never hurts to get it right and the peace of mind you get from triple checking and cleaning everything is priceless.

Yeah, I tend to agree that they will probably not be a problem, but as you say, triple-checking is in order. Looking around online, I see postings on other forums, where people say they have run with scratches and nicks that sounded worse than mine, and drove the engines for tens or hundreds of thousands of miles with no issues.

 

Someone pointed out to me that two-stroke engines have holes in their cylinders (the intake and exhaust ports), which would seem to be much worse than my little nicks.  Of course, those engines may be configured to allow this to happen without damage.  In any case, we'll see what the machinist has to say.

[Dodgeb4ya]

I have a 1/2" X 3/8" x 1/32"" deep pit in the bottom of one cylinder of a straight 8 Chrysler.

It's been there for 30 years or more....a rust pit situation.

Engine has always run fine.

[Matt Wilson]

6 hours ago, Dodgeb4ya said:

I have a 1/2" X 3/8" x 1/32"" deep pit in the bottom of one cylinder of a straight 8 Chrysler.

It's been there for 30 years or more....a rust pit situation.

Engine has always run fine.

Thanks for reply.  Do the rings travel over that pit?

[Dodgeb4ya]

The rings do travel over the pit.

[thisoldtruck]

Matt,

 

I think the suggestion above about magna-flux the block again is a good one.  Then you know for sure it''ll be ok or not something more severe, like a problem in the casting.

 

Andy  

[Matt Wilson]

14 hours ago, thisoldtruck said:

Matt,

 

I think the suggestion above about magna-flux the block again is a good one.  Then you know for sure it''ll be ok or not something more severe, like a problem in the casting.

 

Andy  

Thanks, yes, I will ask the machinist to do that.  It's cheap insurance.  He magnafluxed the whole block before he started work on the engine, but it's possible the boring operation uncovered a flaw in the casting.