Diagnose this... SBC

[Dave Koehler]

Moly rings from anyone will work. Choose your favorite decal.
Let us know what the bore sizing is after the shop does some measuring.

[BeerBudgetRacing]

I ran cotton in the bore and nothing stuck behind. Ran it on the piston skirts and nothing...
So, here are some pics of the rings.

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I don't know whether the cotton is because of a sharp edge or uneven face...

[robert1]

Scrap the rings. There's too much scuffing to risk it. The pistons may polish up with some scotch brite. If the cylinders weren't honed the rings were killed right off. Remove all oil plugs and clean the block again or let the machine shop that hones the block do it. Make sure to remove the plug under the rear cap and the plug at the top of the deck surface rear drivers side. Replace after thorough cleaning. Also I wouldn't run it without plate honing. It's very necessary on a 400 block.

[rfoll]

Absolutely very necessary.

[BrazilianZ28Camaro]

A very good idea is to use MLS steel head gaskets on the 400 SBC. They will distort the bores very little, almost nothing, compared to the ordinary head gaskets. To me they are a must on stock blocks to avoid major problems related to deck distortion.

[Dutchman]

# 2 ring is almost polished square in such a short time. Make sure the next shop is able to produce a quality finish on the bores. Sorry for the hard lesson.

[4sfed]

Are there two rails below the expander . . . or is that a spacer at the bottom of the oil ring groove?

[BeerBudgetRacing]

I believe we were using an MLS gasket. about $100 ea.....

Are there two rails below the expander . . . or is that a spacer at the bottom of the oil ring groove?

They call it a locking ring....

So
Comp1
Comp2

And then in the oil groove:
Oil1
OilExpander
Oil2
Locking

[BrazilianZ28Camaro]

I believe we were using an MLS gasket. about $100 ea.....

Great, they are reusable, just make sure your engine was decked flat with a smooth finish.

Probably the bolt marks on the bores are there because the engine wasn't plate honed, then make sure your machine shop will do that with the same type of head gaskets you will assemble the engine.

Take the pistons to the machine shop and ask if is possible to reuse them after your engine is plate honed (have to check for excessive clearance).

If you do not have the measuring instruments to check the crank main & rod clearances, piston to head clearance, true TDC, ask for the machine shop do it for you.

Do not try to reuse the rings, they are shot.

[BeerBudgetRacing]

Probably the bolt marks on the bores are there because the engine wasn't plate honed

Just to be clear (sorry if this is a dumb question), the bolt marks are the dark parts in the bore just above the bolt holes?
So what is happening is as the heads are torqued down they are distorting the bore slightly causing a slight bulge and more friction as the piston comes to the top. Plate honing will put the bore in a "torqued" condition so the hone will account for the fact that it'll be torqued later and smooth in the torqued state.

Close to an understanding?

[JoePorting]

That piston skirt looks pretty messed up. If it were me I'd probably go with a new set of pistons and rings. If you look at your piston instructions, the spot wore out is probably the same spot you're suppose to measure for final bore sizing which is why I think the pistons are shot.

In either case, make sure you give the pistons and rings you are going to use to the machine shop for proper fitting/honing.

[BrazilianZ28Camaro]

Probably the bolt marks on the bores are there because the engine wasn't plate honed

Just to be clear (sorry if this is a dumb question), the bolt marks are the dark parts in the bore just above the bolt holes?
So what is happening is as the heads are torqued down they are distorting the bore slightly causing a slight bulge and more friction as the piston comes to the top. Plate honing will put the bore in a "torqued" condition so the hone will account for the fact that it'll be torqued later and smooth in the torqued state.

Close to an understanding?

Exactly, but the real problem with the bulge the head bolts cause on the bore is that they unseat the rings, creating clearance between the ring and the bore for the cylinder pressure scape to the crankcase.

Eliminate this problem with a correct plate hone job and you can say good bye to the smoke on the breathers.

If the budget permits, get new pistons, (after the machine shop measure the bores and tell you what piston size you need) because the ones you have are with their life already shortened considerably.

Hope this helps.

[kirkwoodken]

FWIW, the PROPER plate honing of a stock 400 SBC block is absolutely mandatory. The decks are thin and the bolt holes are too close to the bores. Done right, they last forever.

[ParDeus]

Depending on whaf you want to do, I have a block and decent pistons I'd be willing to let you have for nearly nothing.

Also, in the pic of the block, you can clearly see that the deck is cracked near the water hole.

[BeerBudgetRacing]

Depending on whaf you want to do, I have a block and decent pistons I'd be willing to let you have for nearly nothing.

Also, in the pic of the block, you can clearly see that the deck is cracked near the water hole.

Thank you - appreciate the offer - depending on what the machine shop says I may be taking you up on that.

Question: I'm not seeing the crack you are referring to. I cleaned the deck and took a few more pictures. Can you help me locate the crack you are referring to? or maybe it was bad pictures?

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Appreciate you taking a look....