Well good news and bad news.
The good news is I finally have all the oil leaks fixed. The last one was the left valve cover gasket leaking. I couldn't see it on the side of the head, but I finally added some UV dye to the oil and drove it a while. When I jacked it up and shined the UV light on it, there was a brilliant yellow trail from the front of the head, running along it below the valve cover, onto the block, down around the oil filter and down the flywheel cover.
I still had an intermittent water leak, and I finally traced it to the block drain on the right side. It appeared to be leaking around the drain valve, so even though it wasn't loose, I snugged it up a turn or so, and that seemed to stop it. So, yesterday I took it for another drive, and when I came back, it was leaking even more. Today, I removed the drain valve and installed a regular pipe plug. I put sealant on it and snugged it up pretty tight, and the leak got even worse. After a closer inspection the leak it coming from a crack in the side of the block, starting just below the freeze plug and extending down into the block drain boss.
That is not what I wanted to see. Foul language ensued.
The original plugs were run in really tight when I bought the block and stripped it down. I installed the drain cocks when I put it back together, but didn't make them as tight as the plugs had been, so I know they didn't cause it to crack. Whether the crack was already there and propagated as the block heated and cooled, I don't know, but there was no leak there until recently or I would have noticed it.
I have welded some engine blocks in the past, but trying to weld a threaded hole that will be stressed by installing a pipe plug is not a good bet to succeed, in my opinion.
So now I have to either find another Chevy block, which are getting to be pretty rare, and taking a chance on another used block, or replacing it with an aftermarket block, which would definitely be a better choice. Either way, If the used block is standard bore, it will have to be bored to .030" oversize to fit my pistons, and one that is already oversize, it's unlikely it will be the precise sized bores for proper piston clearance. Do I want to put that much into a used block?
A new Dart 400 block will also need to be bored, but at least it will be bored to the correct dimensions. The other possibility would be to buy new pistons to fit the 4.125" bores of the 400 block. I'm going to check to see how the machine work cost will compare to the cost of new pistons.
My guess is that it will be close to a wash.
I'm going to talk to the tech at the machine shop to see what he would recommend, and go from there.
If I do go with a Dart block, Lane Automotive is only 50 miles north of me, and they show several in stock.
Also, the cruise control hadn't been working, so I spent a while troubleshooting that the last couple of days. I had everything coming to the control unit but power. Would have sworn that the first time I checked that pin on the connector, that there was power there. But later when I was double or triple checking everything, there was no power on the brown wire. I pulled the fuse, and it didn't look blown, but it didn't look right, so I changed it, and then I had power to the unit. A test drive showed it was working, though surging in speed, so it needs a change to the gain setting, according to the manual.
I'll report back on what I decide to do.
. I’d start fresh and use what you can, such as heads, intake, headers and just forget about the rest. I’d hate to bore a brand new block just to reuse your pistons. I know nothing about welding a block, your crack doesn’t look bad but they have a way of growing.