How to clean up these case through-bolt holes?

[JonT]

First of all I don't know what was used in these case through bolt holes as an adhesive or sealant does this caked on material look familiar to anyone? RTV maybe after being heated to op temps in an engine?

Also, any suggestions on how would I clean this material off the case so the new washers will seal up the case properly with the o-rings?

[DRACO A5OG]

Use soft brass bristle round skinny wire wheel attachment and use your driver, if brass is too hard use the plastic one with some lite solvent like gasket cleaner, let soak and use the wire wheel. HF sells them cheap. Do not use the steel ones for obvious reasons.

[Dpmulvan]

Ive seen a special white plastic disc made for this issue, not sure where to buy one. Have you tried steam or heat gun ?

[Dpmulvan]

3m makes a tool called roloc bristle disk, they sell them on Amazon. Not sure how well they work or if they make one small enough to get inside the hole,

[tharbert]

OK, I'm just an enthusiast, not a guru of any sort. Not that cleanliness isn't an issue but isn't THE issue here the fact that the hole isn't chamfered?

[prschmn]

The place that's most critical is the counterbore below the face the washer sits-that's where
the o-ring seals. The rolc bristle discs work great but I haven't seen any small enough to
fit in there.
Be careful to follow the methodology when you install the through bolts and o-rings.

[Catorce]

Take the case to an automotive machine shop and have it soda blasted for a hundred bucks. It will look like new.