engine front oil gallery soft plug size and hole

If anyone knows the OD of the outer two front oil gallery soft plugs I'd like to validate before installing them.

1/2" plug is too small, but the 9/16" plug seems too big. But I doubt there's even such thing as a 17/32" plug!

Also I believe the hole drilled in them from the factory is .030", is that also the case?

thanks

I just tapped it with a 1/4 npt. The hole steps down half an inch in. I don't think it'll block anything like the center one will.

I didn't get over to the shop this week to work on it, but thanks for the tip on the hole stepping down to 1/2- so then the 9/16 should be the correct plug.

The idea of tapping the hole and putting in a pipe plug was already tossed around between us but I don't want to put the block back through the washer and clean it up again at this point.

Ok, just wanted to close this as we were able to get around to it today.

.030 (well, .8mm) holes drilled successfully using a Dremel drill press

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The plugs installed just fine. We got the cam, crank studs installed, oil clearances and thrust bearing clearances checked and main caps torqued down. Good progress today.

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...and we weren't supposed to put a hole in that center plug, were we?

I've no idea. Always thought it was just the center one if you were going to drill one.

rauldelp wrote:

I've no idea. Always thought it was just the center one if you were going to drill one.

hah!

I should have paid more attention when I took it apart. If I had known it takes 4 months to get a block machined I certainly would have documented more carefully.

I don't think it's going to affect too much with the instead of one. Can't imagine you'll lose much oil pressure

I don't think it'll matter much either, but I'm sure if it will someone around here will say so.

If anyone looks for this later, the GM part number for the plug with the hole in it is/was 10110897. The description for the part says
the plug is .57" diameter, .25" deep and the hole is .025" (or .0635mm since small metric bits seem to be easier to come by)