Piston Damage Salvageable?

[EyExR]

So I tore my engine down after failing a leak down test.. Piston #3 had a broken oil ring. And Piston #5 had a cracked oil ring AND ring lands...
These are images of each cylinder's bore, piston, and head. Still on the fence of what to do but I may just get a new piston to replace the cracked one, re-ring the culprits and give it a shot. My concern is actually the pitting on the top of piston #4. The bore walls seem to be smooth with no nicks.

Any engine builders out there with opinions on this?

Cylinder #1






Cylinder #2






Cylinder #3






Cylinder #4






Cylinder #5






Cylinder #6

[djjerme]

The more important thing to look for, is scaring in the cylinder. If you find any gashes/ridges that catch a fingernail - ideally, the cylinder should be bored out. If you don't find anything out of the ordinary, then you could put a new crosshatch pattern in it (hone it out.)

The piston looks like it may have been overheated, and the broken ring lands could be an issue.. If you want to inspect it further, soak it in some ATF and give a gentle going over with a soft brass brush. You could see if some else has a set of pistons they are willing to sell you.

I have done a single piston/rod swap, when I had a bolt get sucked in to the #1 cylinder on the race car..

The head will need to be resurfaced though, looks like the head gasket ring started to let go..

[EyExR]

The more important thing to look for, is scaring in the cylinder. If you find any gashes/ridges that catch a fingernail - ideally, the cylinder should be bored out. If you don't find anything out of the ordinary, then you could put a new crosshatch pattern in it (hone it out.)

The piston looks like it may have been overheated, and the broken ring lands could be an issue.. If you want to inspect it further, soak it in some ATF and give a gentle going over with a soft brass brush. You could see if some else has a set of pistons they are willing to sell you.

I have done a single piston/rod swap, when I had a bolt get sucked in to the #1 cylinder on the race car..

The head will need to be resurfaced though, looks like the head gasket ring started to let go..

Thanks for your reply.
I don't feel any cuts or ridges on any of the cylinder walls. I'd also like to skip the hone as that will only introduce more material into the engine and I would like to avoid removing anything else if possible.

Where do you see a head gasket ring letting go? I've resurfaced this head too many times now I think... I'm already using the thickest gasket possible.

[djjerme]

Cylinder 4 - in your photo, the upper left hand, where the gasket would seal, doesn't look so hot. Even Cylinder 5 doesn't look as good as I would like to see. Also, all that pitting in Cylinder 5 is going to create hot spots in the combustion chamber. You should at the very least try to smooth that surface out with some mild porting.

The ideal combustion chamber is a smooth globe shape (think hemi head design) which allows the flame front to burn evenly through the fuel/air charge. Any intrusion or rough surface in the chamber can cause turbulance in the flame front, leading to unburnt fuel, or hot spots that cause pre-ignition (pingning) which can cause small divots in the aluminum of the piston, and given enough time, burn a hole in the piston..

I would seriously look at a better head if can find one...

You can do a bead hone just to get the crosshatch pattern back in it. Put something at the bottom of the cylinder. If you are doing it fine enough, then there shouldn't be any heavy shavings. You only want enough to break the glaze on the wall and allow the new rings to seat - otherwise, that cylinder will never seal. Just run the bead hone up and down the cylinder for a couple passes to create a 45 degree pattern, then wipe it down really well with cleaner and oil it up.

[EyExR]

Cylinder 4 - in your photo, the upper left hand, where the gasket would seal, doesn't look so hot. Even Cylinder 5 doesn't look as good as I would like to see. Also, all that pitting in Cylinder 5 is going to create hot spots in the combustion chamber. You should at the very least try to smooth that surface out with some mild porting.

The ideal combustion chamber is a smooth globe shape (think hemi head design) which allows the flame front to burn evenly through the fuel/air charge. Any intrusion or rough surface in the chamber can cause turbulance in the flame front, leading to unburnt fuel, or hot spots that cause pre-ignition (pingning) which can cause small divots in the aluminum of the piston, and given enough time, burn a hole in the piston..

I would seriously look at a better head if can find one...

You can do a bead hone just to get the crosshatch pattern back in it. Put something at the bottom of the cylinder. If you are doing it fine enough, then there shouldn't be any heavy shavings. You only want enough to break the glaze on the wall and allow the new rings to seat - otherwise, that cylinder will never seal. Just run the bead hone up and down the cylinder for a couple passes to create a 45 degree pattern, then wipe it down really well with cleaner and oil it up.

Thanks for the detailed reply! I agree with you about the head. It looks beyond repair, really. If I decided to continue with this engine (and I'm starting to lean away from that) I'll go ahead and remove the crank and everything, have the cylinders measured for roundness, hot tanked, honed and decked again. I still am at a loss to what caused the detonation to begin with. By the looks of it, the temps got WAY hot in there for some reason.

[TobyB]

Have the injectors flowed and cleaned. A partially- blocked injector will do just that-

the lean pot runs really hot, and causes damage like that.

Generally, you never replace rings without honing. The hone allows the ring to seat
to the bore, and shape the bore to the ring. They typically just don't seal well if you don't hone.

And I agree, look for a different victim- the block may be good for boring, but I'd
spend money on getting it checked, first. The head- not so much.

t

[jeffnhiscars]

IMHO those Pistons seems pretty beat up and if you've got cracked lands and rings I suspect it would be money better spent finding a used engine. If your head is shot as well then you would be $$$$ ahead to find an exchange