I had to be sure

There were no internal leaks so I pressure tested the block at home.

Results??? Are we seeing a crack there below the cam journal?

No cracks,No leaks Thank you!

Smart move.

well, at least you got the block ready for paint

I got the block re honed after finding this and had to be sure.

Cast iron can be cracked and not leak when pressure tested at room temp.

You need to make that available for rent. Nice.

Thanks! I got the plastic out of the garbage when I was a garbage man,it was a freezer door.

Just outta curiosity, what block is that?

Koleno block #33

Like chip said just air at room temp may not show, been there had that happen. You may want to do add hot water to the test!

Very true need to get it heated up as if it were running

Now that I tested it I am confident the Moroso sealer sealed any leaks.You are welcome to explain how you would heat the block tho.I did have a plan.

Here is what I made to find a 'hot only' leak on a complete engine. I'm sure you can do something similar with the empty block after a little thought.

Wow that is quite a getup.I have a 125,00 BTU heater to bring the block to temp and then pour hot water in and seal it.I would use a temperature gun to check things.

I had a cylinder in a 360 block that looked like yours, but couldn't see the problem. I ended up putting some water in the block and took a propane torch to the rust area and low and behold it started blowing steam as there was a pinhole in the cylinder wall

Something like this is what I would do first. If that didn't show anything, then I'd try something a little more complex like the pictures w/ the copper worm.

Wouldn't it be easier to just sleeve that cylinder and have no worries then try to fab that crazy heated setup?

There are many ways to test depending on what you have.
https://www.youtube.com/watch?v=c6xrnfQGdko

She is clean,dry.

I hope that was effective. That should have heated the outside of the block plenty, not sure about the cylinder wall.

The water in the block did the heat transfer very well.

If it's not a crack... What caused the big rust spot?

If it were me, I wouldn't be putting this thing back together until I knew the answer to that question.

Good. I didn't know you had the block filled w/ water.

In my perspective I have satisfied reasonable doubt that is will leak again from anything other than a head gasket.

Look... It's your motor...so you obviously can do what you want. So just know everyone is just trying to help.

But even if it leaked from the head, how did the water defy gravity and pool up and rust on the side of the bore?

I appreciate the help don't get me wrong.You pose a good question but we may never find out also.I may have missed that spot looking after the last hone someone did and the rings just never got it and it rusted.

How would the rings or hone not touch every area on a round and straight bore? Are you saying the rusted area was hollow (concave)?
Doug

Yes!

That is what was causing a ton of crank case pressure the blowby in that area.I was getting a lot of oil from the valley tray every run.

How on earth do you hone a new block into a hollow? No way. It was straight when it was honed if the stones touched. I'm assuming this was a new Koleno block honed with a real hone, not ball hone. If it's hollow the bore moved, a lot. Why? How far over did it have to go to clean up? .010", .020", .030"?
Doug

This was the 3rd or 4th bore on the new block and only .001 to clean it up.

Time to file fit new rings in the fresh bore.Speed Pro R-19103 35 Hellfire rings.I have a bench top hand ring filer and a fine file.[I will gap them .030 to .032]

Hows the hone job look now? That prior hone looks terrible, as does the rust spot.

Nice pressure test set up though.

The pattern is good on the new hone and I checked it with a dial bore gauge.