I'm no expert but looks like to much heat. The last picture of the piston shows scuffing in the center of the piston. If it was a loose/ rocking condition I would think you would have scuffing on the top or bottom of the piston.

Another thing I wanted to add is it's really difficult to determine what cylinders are notoriously hotter. Many factors however most of the BBC's with dart heads I've dyno'd were 8 then 2 but If you google it you'll pretty much cover every cylinder from 1 to 8. To many variables right down to aftermarket heads, porting, stock GM heads, intakes, exhaust and on and on. Even a cam. In a perfect world all would be 100 % efficient and even if each port was to flow identacle you'd still have different temps. Did you purchase FF's heads. Also you still keeping wet exhaust I assume due to already known reasons.

Was your original machine shop a known reputable shop? Seems like he might be in need of some new or updated equipment and also purchase a bore gauge. Lol.. Hey we all have troubles but in the end it's all worth it provided you move forward with confident reputable people and get your o2 wb. You'll be able to go boat with confidence free this is all over.

So the mystery of the egg shape cylinders is revealed. While boring the block they found 2 sleeves. Too thin now and moved out of cylinder n their own. Only .034 after boring.

Glad your moving forward. Are those 1/8 sleeves or did you go thinner. If they are it would bring the bore out to 4.655 if my math is right.

Your math is good as that will be very close I think. The shop actually called me today and they ordered the new sleeves. We had a talk about if this was going to be too big of a bore for the the block but I guess they are proceeding. Two of the guys at the shop offered up Dart blocks while I was there. Was tempted but sleeves are way cheaper than a block.

Just make sure your builder sonic test all the cylinders if he hasn't already. The thickness can vary a lot. Casting flaws, core shifts and scale. Especially if it ever seen salt water.

Opinions will vary from machine shop to builder and individual to individual. HP, stroke etc can determine min also. I'd hate to see anything less than .210 - .215 on the thrust side and maybe .040 less on pin side. Obviously more the merrier. It's to bad that happened to you. Boating can suck but worth it $$$$.

So they ended up sleeving the block and it turned out pretty good and has plenty of meat for sure.

Good deal. One less thing you need to think about. You going to go with wideband o2. Cheap insurance especially if your movig around different altitudes. I went with in innovations # 3844 I think and comes with total of 20 ft cable. You can get for 160.00 + -. Numerous others are out there but I ended up wth this one. In fact recently found as my fiancé stashes all my piles of goodies when company comes over. Hate that. Hah. Anyway congrats.

I am for sure going to use the wideband O2. Might have to bit the bullet and buy some real headers too and will have them built with the bungs.