oil galley tap and plug sizes

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farmer_fred
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oil galley tap and plug sizes

Postby farmer_fred » 31 Jan 2016 08:58

Drilled out the oil galley plugs in our L16 block, and preparing to tap them for threaded plugs. I had purchased 3/8 X 18 NPT plugs and a tap, but the tap seems pretty big for the oil galley holes. Do I need to drill them out before tapping? It looks like 37/64 or 9/16 drill size would be appropriate for that size tap.

Any other watch-outs for this endeavor? I don't want to screw up the block now!

Thanks,

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zKars
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Re: oil galley tap and plug sizes

Postby zKars » 31 Jan 2016 13:56

I seem to remember this is discussed in the "how to modify your Datsun" book.

The one item I remember, other than chip control, is that (at least on the L24/28) there is a oil hole down to the front main bearing just inside the front hole, that you of course must NOT block with the plug you're inserting. I don't remember the plug sizes that get used. Seems to me though that 3/8 is too big.

farmer_fred
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Re: oil galley tap and plug sizes

Postby farmer_fred » 31 Jan 2016 16:10

Well, 3/8 NPT it is. I was worried about drilling too deeply, but then realized I have a drill press with a depth stop. I only drilled as deep as the original steel plugs were crammed in, and then modified my tap with a lot more taper after starting both holes to allow me to get the tap a littler deeper w/o needing a deeper oversized hole.

That oilway is at the front end of the galley. I tapped just deep enough to tighten up with some of the plug protruding, and ground down the face of the plug so it was below flush.

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Hakosuka510
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Re: oil galley tap and plug sizes

Postby Hakosuka510 » 11 Feb 2016 23:02

The Dorman freeze plug kit for the L16/L18/L20b actually comes with two 3/8 NPT plugs for the oil galley. We just installed them with zero issues. No danger of blocking the passage mentioned above and no grinding of the plug required. The pack was short one freeze plug, though... :roll:

510rob
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Re: oil galley tap and plug sizes

Postby 510rob » 12 Feb 2016 10:59

Now check that the inside end of your plug isn't blocking the oil feed to the #1 main journal (stick the butt end of a drill in there and see how far it goes, then compare it to the #2 or #3 or whatever). If you put a plug in there a bit too far, you can (partially? fully?) block off that (rather critical) passage.

farmer_fred
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Re: oil galley tap and plug sizes

Postby farmer_fred » 13 Feb 2016 07:15

510rob wrote:Now check that the inside end of your plug isn't blocking the oil feed to the #1 main journal (stick the butt end of a drill in there and see how far it goes, then compare it to the #2 or #3 or whatever). If you put a plug in there a bit too far, you can (partially? fully?) block off that (rather critical) passage.


Yep, all good there. The new threaded plug isn't even as deep as the factory pressed-in steel plug.

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Byron510
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Re: oil galley tap and plug sizes

Postby Byron510 » 13 Feb 2016 17:38

You read my mind Rob; Farmer, good that you checked. This very mod has killed more than one engine over the years by inadvertently blocking the #1 main feed.

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