Cap located behind carb on DC Case

(quoted from post at 21:49:23 04/04/16) I removed my carb to rebuild it and noticed a small flat head cap on the engine block directly behind where the carb was mounted. A end view of the engine block in my service manual shows what looks like a small chamber inside the block at that location labeled "tunnel type lubrication" I guess the question is what is the external cap or plugs purpose? Thanks

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(quoted from post at 13:20:01 04/05/16)

(quoted from post at 21:49:23 04/04/16) I removed my carb to rebuild it and noticed a small flat head cap on the engine block directly behind where the carb was mounted. A end view of the engine block in my service manual shows what looks like a small chamber inside the block at that location labeled "tunnel type lubrication" I guess the question is what is the external cap or plugs purpose? Thanks

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You are looking at the end of the drilling for the main bearing, the bearing bores are drilled, the holes then are tapped to plug off the hole, there should be a similar plug at the front of the block also and the main outlet for the oil filter and gage which is a lot larger thread,

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