Dropped off the new heads, old valves/springs, seats, retainers, etc… to the machine shop today. They will call me when the valves are cleaned up and we. An go from there.

the block deck is good. It had not been cleaned yet. Started on cleaning the old gasket with CRC gasket cleaner. Comer right off. Tedious but it works well. Trying to be careful not to let debrie fall into the water jackets and oil holes. Cleaning the pistons in place as well.

I'm no expert in engines but.... cleaned off the block deck in preparation for the heads, then decided to also clean up the pistons.... The pictures speak for themselves. Looks to me some detonation. This is in a 25' Carolina Classic, so not trying to break any speed records. Usually I'm cruising at about 35-40mph at about 3300 RPM area. (can't remember....it's been about a year). Thoughts on replacement pistons? Pulling block out and will disassemble and send to the machine shop. Would be nice to get a bit more power out of it. The Volvo DP-E drive has a 425HP limit though. Not looking for more than that.

This is the NON HO 8.1L from Volvo Penta. Rated at 375HP.

Yikes... you may want to think about getting a price to bore over your block while replacing pistons... looks to me like there's also some pitting in the cylinder wall in your 8th picture.. maybe it's an illusion.. but going thru the hassle of replacing pistons and rings is a lot of work.. is be inclined to at least have the shop take some measurements of the bores, and crank journals and see if everything looks usable.. just my .02

Yup...

After disassembly, the block will go to the shop and have them do their thing. I'll wait for them to see what they say before ordering anything. This is all just incidental findings. From the corroded exhaust ports to now this. All I planned to do was upgrade from the stock manifolds to aftermarket to end reversion. Looks like reversion did the damage long long ago with a previous owner and I'm now finding all this now. Glad I'm seeing this now vs having it break apart while running.

not sure if you're interested, but keeping in the back of your head I do have a brand new block never been used. It's been all machined ready to go. I've had as spare that I've never used.

To answer your questions on pistons, Wiseco has forged pistons specifically for the 8.1 in various sizes. I've used several sets, they run good. (part #s PTS524AS, PTS524A3) These pistons use a traditional piston pin size of .990 like earlier big blocks, so you'd need to replace the rods with 6.7" big block chevrolet aftermarket rods when you do that. There's lots on the market for 6.7" rods. (example Scat 2-ICR6700-7/16)

The valves should be changed out. The pitting will increase they're operating temps.

The piston pitting is classic water corrosion/erosion.

Guides: for the most part, the best wear resistant guides are cast iron. Pressed in iron guides may be a better iron for guide wear vs the head iron.

Alternatives are bronze liners or full bronze guides. Liners are cheap, and can last a long time if setup correctly. Less valve to guide clearance is better for wear, but the valve also need to be setup correctly. Chrome valve stems etc.

Guides need to be sized correctly and straight. Broached to size is not sufficient. They need to be honed.