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Discussion Starter #1 (Edited)
A recently acquired 2 liter spider was showing low oil pressure. My first plan was to ignore it and believe that the gauge/sending unit was lying. Once the low oil pressure light started blinking at idle I knew it was time to pull my head out of the sand and fix the problem.

Oil pressure was pretty decent cold but as the engine heated up the oil pressure would fall to apparently dangerous levels. Other than the oil pressure the motor runs great and I really didn't want to tear into it too deep if I could avoid it. My gut sense was that the bearings were worn and I had hoped I could install new ones without pulling the crank (which I ultimately decided was a bad idea).

So we pulled the motor and checked the main clearances. A little on the low side but still in spec and the both bearings and crank surfaces looked and felt fine.

Pulled the oil pump and felt that the piston might be a bit sticky so we replaced it, buttoned up the motor and ran it off on the test stand. No significant improvement and so we were faced with pulling the motor apart after all (worth the try anyway).

After pulling the crank out we checked the main and rod journal diameter but they were almost perfect - still no clear reason for the drop in oil pressure.

The crank sat on the bench for a few days as we busied ourselves with other projects but my plan was to have the crank ground and install oversize bearings. Still this was dumb thinking since nothing suggested that it was needed but I was fixated on bearing clearances...

So I was moving the crank yesterday and lo I happened to notice this:

IMAG1946.jpg

That was one funky oil plug thought I, a possible source for oil leaking and possibly the cause for the low pressure. We wrapped all the journals with electrical tape to plug the holes. Then we blew air through one of the holes and sprayed the plug with soap, looking for bubbles. None were forthcoming but I suddenly was aware that air was rushing out somewhere. That's when I noticed this:

IMAG1947.jpg

Duh! As it turned 2 of the six plugs were missing and the four plugs that were there were so mangled it defies explanation. Curiously the two missing plug holes were threaded which deepens the mystery as we never found any grub screws in the sump (or elsewhere for that matter).

The amazing thing in all this is that despite the missing plugs there was no damage to the motor. As I said, the journals all measured good - I am going to replace the bearings of course but that's a small price to pay.
 

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Yes, that does happen to the 4 cyl Alfa engines now and then. Been a problem for decades.

You are wise to avoid grinding the crank. If they all read within spec, no reason to touch the journals at all.
 

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As it turned 2 of the six plugs were missing and the four plugs that were there were so mangled it defies explanation. Curiously the two missing plug holes were threaded which deepens the mystery as we never found any grub screws in the sump (or elsewhere for that matter).
Congratulations on finding the obvious culprit for your low oil pressure! Nothing is as frustrating as disassembling an engine and finding that everything seems OK.

It is interesting that the missing plugs were the ones that were threaded. Of course, you may find that all your plug holes are threaded, but someone banged aluminum plugs into them.

It is also interesting that the missing plugs have vanished. Whether steel or aluminum, you would think that at least one of them would have lodged somewhere in that complex oil pan.

I assume you are going to remove all of the plugs, and re-do them. Will you use threaded plugs, or the factory-style aluminum?
 

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71 Berlina 74 GTV 17 Giulia Q4
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You could have the crank polished just to go back to new. No signs of locktite? I would say I use red on my plugs and never had any come out but I don't want to jinx myself.
 

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Hi, your missing grub screws or aluminum plugs may have exited the sump via oil changes. I am very happy with my threaded oil passage holes, grub screws and red loctite. Dennie
 

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Discussion Starter #8 (Edited)
Hi, your missing grub screws or aluminum plugs may have exited the sump via oil changes. I am very happy with my threaded oil passage holes, grub screws and red loctite. Dennie
That is a good point. We've changed the oil a few times and while I usually give a look for foreign stuff I can't say that I remember doing that this time.

Whenever we rebuild a motor we thoroughly clean the oil passages - I don't know how you can do that without removing the plugs. And although the plugs have worked successfully for years I just feel a lot better replacing them with grub screws and red locktite. This goes for the crank AND the block. Future rebuilders will thank us.

I do think it is wise to have a pro tap the holes in the crank - clearing a broken tap is no fun.
 

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No locktite... The pictures are as found. I will use the red stuff.

Isn't it interesting how we sometime overlook the obvious, even when we know better? Been there and done that more times than I can count. Of course we're always supposed to suspect crank pins falling out . . . only just not on one of my motors!

If you put in the regular aluminum crank pins with locktite they'll stay in just fine and you can save the expense and trouble of putting in Allen-head screws.
 

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71 Berlina 74 GTV 17 Giulia Q4
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Since the holes appear to be tapped I'd use screws, otherwise, yes on the al u min e um plugs and red.
 

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Discussion Starter #11
Isn't it interesting how we sometime overlook the obvious, even when we know better?....
Yes, exactly! I will say I'm surprised that I was getting any oil pressure at all and that I wasn't spinning bearings... Been there, done that :crying2:

...If you put in the regular aluminum crank pins with locktite they'll stay in just fine and you can save the expense and trouble of putting in Allen-head screws.
Cost isn't a big issue - the grub screws: $0.10 each, plugs $2.30 each. The machine shops around here charge about $25 to tap the six holes but we know how to tap them so the cost is insignificant.

If I were to plug them I could still sleep at night but I prefer the grub screws...

I think the real point is that if you are going to the time, trouble and money to tear down a motor, spend the extra $15 to $50 to R&R the plugs so that you can clean the oil passages. In stands to reason that if you grind a crank some of that crud is going into the oil holes and those plugs are areas where that crud can hide. Even if you don't grind the journals, as the bearings wear some of that bearing crud is bound to end up in the nooks and crannies of the oil passages. Pipe cleaners and flushing can only do so much.

Maybe it will all stay there forever... or maybe it will come out while you're running down that dark desert highway, cool wind in your hair (sorry, radio is on in the background...)
 

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71 Berlina 74 GTV 17 Giulia Q4
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Yup, there was a grey thick sludge like goo behind the plugs I just replaced in the motor I'm currently rebuilding. I like your logic behind removing the plugs, a little effort for a lot of peace of mind. I would say it also applies to having the crank polished:) check out radiofreetexas.org
 

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When I built my current motor I used a short block from an '86ish Spider that I bought for $100. I don't know the mileage but I think it as under 100k. I rigged up a fuel pump in a bath of kerosene and I recirculated the kerosene through the crank passages for 10 or 15 minutes. I noticed some dark stuff come out in the first minute but after that it did not change much. I am happy that the oil passages are at least as clean as they need to be, after all my Verde had 160K+ on it and it had never been opened. I also re-used the rod and main bearings. I cleaned them up, labelled them of course, then checked them with plasti-gauge. They were well within spec. I talked to RJ before I made these decisions. As you probably know, I have a very strong motor with terrific oil pressure that is revved to 7000 rpm very frequently. Of course, it may fail tomorrow but I think that is unlikely. I think that some of you guys are a bit anal about the crank galleys.
Rich's plugs probably fell out because someone had dicked with them.
 

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71 Berlina 74 GTV 17 Giulia Q4
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Although I've never had it happen to me I have friends and have seen it enough here to know that factory plugs do come out with a frequency that gives me pause. So I put new ones in with red and since they are out might as well clean the galleries. Call it what you will.
 

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This might be the first time an electrical engineer called a mechanical engineer anal!!
It's not the first time that THIS EE called an ME anal! We are just rule of thumb engineers.
 

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Grub Screws

Why opt for grub screws? Why not use NPT?

I too found that I had a missing plug from my crankshaft. I had planned on using 1/8-27 NPT plugs to seal the passages.
 

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71 Berlina 74 GTV 17 Giulia Q4
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That's what we like to see! Congratulations!
 
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