Factory threaded 2.0 crankshaft! - Alfa Romeo Bulletin Board & Forums
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post #1 of 33 (permalink) Old 03-02-2010, 03:10 PM Thread Starter
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Factory threaded 2.0 crankshaft!

I'm restoring my '90 spider 2.0, although the engine seemed to be working properly, I wanted to clean the engine internals, specially the crankshaft oil galleries ,I was also a little concerned about the possibility of a crankshaft plug to be loosened, so I planned to modify the crankshaft to install threaded plugs.

Today have been the time to disassemble the engine, and what was my surprise when I found that the crankshaft comes with threaded plugs from factory

I have no read any (if I remember well) thread indicating that the 2.0 motronic engine have threaded plugs, or maybe my engine was modified before??? (I don't believe so)
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- SNO Director, Spain branch, Barcelona
- '90 2.0 Spider -- '93 164 QV -- '93 155 2.0 TS -- '02 156 2.5 V6 -- '?? FMG 3.8 Project
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post #2 of 33 (permalink) Old 03-27-2010, 04:16 PM
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Bump

This is news to me!
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post #3 of 33 (permalink) Old 03-27-2010, 04:32 PM Thread Starter
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Definitely it is not a modification, it comes from factory. The setscrew is M8, not M7 as the modification suggested in Jim K. book.

To take out them I broke two allen tools!!! (they were fit with thread locker).
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- SNO Director, Spain branch, Barcelona
- '90 2.0 Spider -- '93 164 QV -- '93 155 2.0 TS -- '02 156 2.5 V6 -- '?? FMG 3.8 Project

Last edited by FMG_V6_btb; 03-27-2010 at 04:40 PM.
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post #4 of 33 (permalink) Old 03-27-2010, 05:50 PM
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Newbie question: what is the function of the crankshaft plugs? Why are they there? Do all crankshafts have them?
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post #5 of 33 (permalink) Old 03-27-2010, 06:13 PM
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Hi TorW,
Here is a quick, simplified answer.Most crankshafts are "cross-drilled" to carry pressurized oil to the bearings. The only way to create a gallery through the crankshaft is by drilling it. The "holes" were access holes for the drilling, as the gallery interconnects within the crankshaft. The drill access "holes" were factory plugged with aluminum plugs. With Alfa's, it has been found that sometimes, not often, these aluminum plugs will come out and allow the pressurizes oil to escape from an unintended area. On Alfa engine rebuilding, it becomes an optional procedure to drill out the aluminum plugs, and tap the drill access hole for a screw-in type plug as shown above. The plugs are usually sealed with Loctite Red, preventing them from unscrewing. To remove them for gallery cleaning, heat needs to be applied, directly to the cap plug, with a torch. They then can be removed. Threading for these in a hardened crankshaft, can be difficult, and break taps. The easiest way is to grind through the hardening with a die grinder before attempting to tap. The hardening is usually about .020" thick. Even then, this requires some patience, as the crankshaft is still a hard forging. The reason this is not done by factories is a matter of time and labor. Also, for most applications, the OEM aluminum plugs are adequate.


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post #6 of 33 (permalink) Old 03-27-2010, 06:16 PM
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Yes, cranks have plugs where the oil galleys are plugged. It's impossible to get oil form one point to another in the crank w/o going around corners, and that's just something a drill can't do, so they drill in at different angles and intersect the drillways to make passages.

The purpose of the galleys is to route oil to the bearings, the purpose of the plugs is to get the oil pressure up, as without them, the oil will take the path of least resistance and never actually build any real pressure: it'll come out the holes, which will leave the bearings running at severe underpressure if not practically dry.

You'll stumble across a thread now and again where someone lost a peened in crank plug and thier oil presure immediately dropped to almost zero. Hence the desire to replace them with the obviously more reliable threaded fixtures.




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post #7 of 33 (permalink) Old 03-27-2010, 06:17 PM
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*sigh*
Typing slow again.

Hi Gordon :wave:




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post #8 of 33 (permalink) Old 03-27-2010, 07:06 PM
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I love multiple answers that express variations on a theme. Everyone learns something.
(Moreover it gives me courage that I have not opened my mouth, or keyboard, and inserted my foot!) Thanks Darren!


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post #9 of 33 (permalink) Old 03-28-2010, 05:41 AM
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Thanks! That's one less mystery

So, the holes where the plug sits are leftovers (for lack of a better word) from crank production, and you can use any method you want to plug them provided the plugging can withstand pressure and the crank can be (or still are) balanced?

And, will a peened plug that falls out simply come to rest in the sump?
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post #10 of 33 (permalink) Old 03-28-2010, 12:04 PM
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Quote:
Originally Posted by TorW View Post
and you can use any method you want to plug them provided the plugging can withstand pressure and the crank can be (or still are) balanced?
Not neccisarily 'any' method, as you wanna plug them with something that can be removed in the future so the drillways can be cleaned of ish that'll build up over time.

More ish = more restriction to oil flow to the bearings (but the oil pressure will look great)

As said previously, the peened in plugs are just fine for stock use, and threaded set screws are for the hotter stuff. there's really not much sense bothering with other methods, unless mabe you wanna be the lab rat


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And, will a peened plug that falls out simply come to rest in the sump?
Yup, that's where they'll end up whether intact, or perhaps a bit chewed if they got caught up in the rotating stuff before dropping down.




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post #11 of 33 (permalink) Old 03-28-2010, 12:08 PM
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Quote:
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(Moreover it gives me courage that I have not opened my mouth, or keyboard, and inserted my foot!)
bah, you just gotta remember that you got more arse than they've got teeth




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post #12 of 33 (permalink) Old 03-28-2010, 02:04 PM
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My gut tells me you are not the first one in there.
a plug could have failed very early on and it was done at that time.

but with alfa you never know. it might have been a prepped for a race car and not needed so it went into the crank bin to be put in the next motor. or there was a mix up.

or could a class need n OEM cranks to have the plugs before they could do that in a race motor......

that is my guesses

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post #13 of 33 (permalink) Old 03-28-2010, 03:13 PM
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Torw,

This is the other version of plugs and most Alfa's have them. The aluminum plugs are hammered all the way in.
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post #14 of 33 (permalink) Old 03-28-2010, 11:25 PM
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That's brilliantly funny:

'Do not mar the bearing surface, or even touch it with a fingernail for fear of ruining the machined surface, but beat hell outta the rough cast part with a hammer and punch'




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post #15 of 33 (permalink) Old 03-29-2010, 03:09 AM
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I'm glad I made you laugh Daren. How else would you do it? With gloves, maybe? lol

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