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crank oil-galley plugs


matria

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Hello everyone,

I got my block and crank back from the machine shop and everything went as planed but then I get a call from them asking about these oil galley plugs. It seems that someone brought in an L28 block and crank, after I had my work done, and had these plugs taken out for further cleaning. They found some hard ugly stuff in there. the other guy said that the motor had been sitting for a few years. My question is do I need to remove them, clean and tap for NPT plugs? The "How to Rebuild" book does not mention them. The "How to Modify" book says to do it for race prep only. I hate to take the crank back to the machine shop but...

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The galley plugs are in the BLOCK, not the crank. But I'm sure you don't want to take the block back either.

I don't think (almost positive) the Machine shop (Diablo Engine & Machine in Dublin) removed my Galley plugs when they rebuilt my L24 Short Block last year. Engine and Oil pressure have been fine since, but I haven't put a lot of miles on it.

I would think the machine shop should have pumped a lot of solvent through the oil passages when servicing the block, and if flow seemed restricted should have addressed it at that time. Who is did the work for you?

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Matria,

There's a lot of "ifs" involved to determin if you need to remove the crank galley plugs. If you had the crank hot tanked, as opposed to just solvent cleaned, it is good insurance to remove, tap, clean, etc. The reason for this is two fold. The small plugs are aluminum, and if the bath was particularly acidic, they can erode and leave ugly stuff inside. Combine this with a little leftover sludge that was softened up by the acid bath, and its not something I want getting on my new engine bearings. The next " if " - the crank was ground, grinding sludge can hide in the galleys and come back to haunt those new bearings. On the "not necessary" side- If your engine was relatively clean inside with no damage, and the crank was just polished and solvent cleaned, you will be safe returning it to service without changing out the plugs. The galley's are drilled to 6mm dia. at the factory. Some shops will press in replacement plugs, (not preferred) or drill out the hole to accept 1/8 NPT plugs because they don't have the proper size tap. ( too much work, and can screw up the balance.) The correct repair for the Datsun crank is to buy a couple of 1/16 NPT taps, ( the crank is fairly hard and its easy to bugger a tap) and some extra 1/16 pipe plugs, ( so you can test them in the crank while tapping to set the proper depth of thread, the plug should be flush when tight.) Then install new plugs when cleaned for final assembly. For race engines that will be rebuilt frequently, I use blue Loc-tite on the plugs. But for a street engine thats hopefully going to be going for thousands of miles, you might want to use red Loc-tite.

Phred

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Carl,

There are 6 diagonal oil passages in the crankshaft that transfer oil from the main journals to the rod journals. So each rod bearing is fed by a single main bearing. These 6mm I.D. diagonal holes exit near the rod journal and are plugged at the factory, and after time, grit and sludge gets packed in behind the plugs by the centrifugal force of the rotating crank. The L6 crank works great for the street as all the journals are cross drilled (except for the rear main). To race prep a Factory L6 crank oil system, the rear main journal is cross drilled, and an additional 6 diagonal holes are drilled through the crank to connect each rod journal with a second main journal. That way each rod journal is fed by two main bearings, and allows the bearings to survive extended high rpm use. Fun huh?

Phred

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Thanks for the great information, Phred. Us shade tree types can learn alot from a professional like yourself.

I'm starting to vaguely remember a diagram in the FSM that may have shown the diagonal passages you mention. I'll have to dig it out and do a bit of reading tomorrow.

Thanks again for clearing things up.

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To race prep a Factory L6 crank oil system, the rear main journal is cross drilled, and an additional 6 diagonal holes are drilled through the crank to connect each rod journal with a second main journal. That way each rod journal is fed by two main bearings, and allows the bearings to survive extended high rpm use. Fun huh?

Phred

I remember reading about this procedure in the "How to Hotrod and Race Your Datsun" book. It was my first book on Datsuns I ever owned and I read it so much its in tatters now!! If I recall, there were two versions of this book. The second one covered more models than the first which I think basically dealt with the 510.

FWIW,

Chris

post-5906-14150794547914_thumb.jpg

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Wonder why they used the same picture and design for the cover of the book I have and the different book that Chris referenced?

Hey Carl, in my copy of the book, it has a short preface as to how they included the info from your book into the one I have. I got mine back in 1985.

Chris

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Carl,

Tim Morgan from Morgan Machine & Marine, Walnut Creek, is the person that I have been working with. I am very happy with everything they did. I felt very comfortable with Tim and trusted him completely. They will be the first people I call the next time I need machine work.

Skip

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