It looks like a small piece came off the bottom of one of my cylinders in the block.
Do you think I should be concerned since its at the very bottom or attempt to replace this block?
You can see it in the lower left of the top cylinder.

 

I'm about to invest money rebuilding the rest of the engine, and am worried a piece could come off and wreck all my hard work.

 

I don't see it being a problem. It's not in the area that's swept by the rings, and it's not in the direction of piston thrust. If it makes you feel better, though, your machine shop can probably sleeve it, which is a perfectly good repair, even for a performance engine.

 

Thanks Tom, I am going to just go with it prolly. It was cylinder 6 on my 4.3 and when it was knocking that was the one smoking and getting the hottest it seemed. It was a cracked cylinder head I think as well. Still verifying this.
If the measurements on the cylinders still check out, I won't worry about it.

 

I'm wondering if it's cracked around the chip. Is the block out? Can you get it x-rayed or magnafluxed or whatever they do?

 

It is out, its so heavy I wasnt going to get it checked. I am bit concerned. Im thinking if I verify that a cylinder head is cracked. Which I havent yet but will this week hopefully.
What are the odds the block is cracked and the cylinder head are cracked. I would think its one or the other.

 

I dunno, that's kind of a tough one to decide. I'm wondering what caused that chip in the first place.

 

I guess its just heat and the rod knock that caused it.

I suppose this block couldnt be bored out, specially now. If it was bored out there would be nothing there since the wall is so thin at the bottom.

 

I'm not sure it is chipped. The location triggers some memory from my engine build. Have to go and take a look.
This could as well be from the machining of the distributor hole.

Anyway - the chip itself in that location should not cause any problems as said before outside of the area where it will hurt.
IF it is a chip I would be more concerned why. A chip like this would most probably have gotten a hit from the inside of the bore towards the outside. But nothing visible from the picture.
If the engine has overheated a very, very careful look for cracks is required. A machine shop should be able to check. In these locations I would suggest a dye-check. In order for that the block needs to be hot tanked (washed/degreased).

If it has no cracks just deburr the edge, making sure either the bore is not touched or it gets honed or bored and honed anyway.

As for blocks that have overheated take measurements of the bores looking down into it at 30 to 45 degree increments over 180 degrees (like a watch at 12'o clock, 1:30, 3:00, 4:30, 6:00 at least and over the whole length of the bore at 1 inch steps. Only way to determine if a bore is warped. (Don't ask me how I know. Same build-thread post #72)

Have a look at my build-thread (in my signature) in post #66 you can see a similar cut-out in the cylinder. (Second-last picture of the post)

 

Thanks for the reply error401. The dye check would be a good idea.
Let me know if you have a similar chip in yours perhaps it is the way they are made.

That was my first instinct but given the condition of this engine I'm not so sure. I will do what you mention about taking the bore measurements.

I just realised I have to buy a telescoping gauge to complete that part. Just finished making my little machine for pressure testing the heads, will try it tomorrow.

I'm definitely getting a telescoping gauge.
The most important two measurements I think are piston to wall clearance and piston ring end gap. Then plastigauge the crankshaft, and I should be good to go.