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1978 Spider 1984 Spider
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Discussion Starter #1
I suspect I'm missing a crank plug or two...oil pressure at cold idle is very low, like around 10psi. max is 50ish around 5K. Once the car warms up a bit the low oil pressure light comes on at idle.

Previous owner notes state that 2 plugs were found in the lower pan. The old pins were reinstalled and "peened". Not brand new plugs. I plan to drop the lower pan this weekend and see what I find.

The question is can you re-use crank plugs that fall out? I would think not since the sides have already been compressed once before and they lost their grip. Even with Loctite I don't think you should re-use them.

Peen or Stake? What exactly is that. everyone talks about it but no one describes the actual process. I would think you are trying to deform & collapse the hole in the crank so that the plug cannot slide out. But this would require the plug to be driven slightly below the surface of the crank. Or is this about deforming the end of the aluminum plug?

For some reason Google was not helpful

How many plugs total are used? But I guess you would not replace a plug that was still in place so it's more an academic question.
 

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I've never dealt with this issue (yet) but many say the right thing to do is drill them out, flush the passages well and tap them to accept plugs. I imagine a balancing would then be in order..
 

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This is from the Overhaul Manual. I'm not sure what tool A.2.0103 does. I didn't replace mine when I rebuilt the motor because I thought it best to leave well enough alone there. I had the crank shaft inspected and the journals polished, and the shop said everything else was good. I've heard of drilling them out, tapping them, and locktight an Allan plug in the hole. The crank is nitrided so that's a job for a machine shop. Are you sure it's not the sender? Here's a problem similar to yours.




1625766
 

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When something is peened or staked in place, it becomes retained by means of raised metal surrounding it. That can be done with a punch or chisel; I prefer a small punch to dimple the steel thus creating a stop, or small raised crater that holds the plug securely in place. These plugs I would peen punch twice, at 180 degrees.
The same thing applies to the special locknut on the flange of the differential... it is staked in place with a chisel edge once the torque is set. And looking at the back of the V6 mechanical tensioner, the internal spring end is staked in place by raised aluminum ridges.
 

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That's good, for those that understand what was done. NOTE, the dents retain the part by creating a reduced diameter to the mounting hole.
There.
 

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1978 Spider 1984 Spider
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Discussion Starter #7
I've seen that thread above and that is not the issue here. It's not a gauge problem. Already checked actual pressure with a mechanical tester. Oil pressure very low at cold idle and light on at hot idle.

I figured the staking was somehow using a punch or something to strike the edge of the hole to make it deform inwards to partly cover the plug. Making the edge of the hole slightly smaller than the actual plug so it won't back out.

I've got that overhaul picture in one of my manuals. But the picture is not a good one nor a close up to show you exactly what he is striking. These are supposedly harden cranks...I'm surprised that you would be able to strike it with a hammer and punch and actually get the metal around the hole to move over the end of the plug. But I guess it can be done.

I just want to be sure I'm hammering the right piece of metal...I assume the crank hole and not the plug end.
 

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The factory tool has a 1/2 inch ball bearing on the end of it. So that when the crank plug is driven in. The tool forms the end of the aluminum plug concave in to the crank.

Not knowing what year your car is. Crank plugs falling out was fairly common from 1972 until the mid 70's. Due to the nitrided crank. After that Alfa figured out how to keep them in.

You can take a long rod and frozen crank plugs and hammer them in. But you will not be able to get the factory tool in there. You will only be able to get to the first couple of pins with the engine in the car.

The best solution is to pull the engine and take the crank out and tap the holes and put plugs in them. The nitriding only goes in a little bit. So with a new quality tap. You shouldn't have any problem doing it. Or just take the crank to the machine shop and let them do it.
 

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Discussion Starter #9
78 spider...says right under my avatar...lol

Not wanting to do the tap and thread (unless a complete rebuild is needed) or I wouldn't be asking about peening the plugs. I like the frozen plug idea, should allow the plugs to go in further before hammering, should allow the metal to expand and grab the crank better. I always do that with sealed wheel bearings. Plus the Loctite would be used as well.

I'm just trying to wrap my head around the actual process of peening or staking the crank. I've staked axle nuts but never a pin/plug in a hole.

So Jim, are you saying that you do not hammer or strike on the edge of the crank hole? But instead only hammer on the end of the pin? Insert the pin fully into the hole and then smash the end of the pin to widen it so it locks against the sides of the hole?
 

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btw if you can't find the plug in the sump, you can buy them;)
Crankshaft oilway plugs.JPG

I might be wrong, but I thought the "special" alfa tool was just a round tipped steel punch of the correct size.....you whacked the tool and the round tip sort of slightly mushroomed the soft aluminium plugs, to help them stay put.
 

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Time to have a look and confirm a plug has fallen out. Quite common for these engines to have low hot idle pressure.

I dislike this part of the Nord engine design. Alfa should have drilled diagonally from one bearing surface to the next like every other manufacturer so plugs not required. Must have been the same "engineer" who designed the coupe door seal method
Pete
 

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Heres the factory tool. It no where near long enough to get to the crank unless you also take off the upper oil pan.
 

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Plus the Loctite would be used as well.
This is not a fun job. I had to replace two crank plugs on my 1974 spider in about 1982. I used new plugs; cleaned the crank holes with lacquer thinner on a Q-tip and coated the plugs with Loc-tite red. The plugs were hammered in using a flat tipped punch. It sounds like a good idea to freeze the plugs but I didn't think of that. I tried to punch the metal of the crank next to the plug hole with a pointed punch but I don't remember that being very successful because the crank was really hard.

At least the plugs stayed in the crank and I sold the car in 1986...

Mark
 

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Discussion Starter #14
Heres the factory tool. It no where near long enough to get to the crank unless you also take off the upper oil pan.
wow...not what I was expecting. So it appears you punch the pins and not the side of the hole in the crank.
 

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Discussion Starter #15
dropped the lower pan this weekend....not one plug??? I was sure I would find at least one crank plug...

I used some wire with a hook bent in the end to fish around in the rear bottom of the upper oil pan looking for dropped plugs...nothing...no dropped plugs.

Do plugs ever fall out and stay in the upper pan or is the pan design such that the plugs will drop into the lower pan?

I was able to look up through the upper pan...I can see one pin and it looks like sh*t...obviously one of the 2 pins the PO had re-staked...it sticks about 1/8" out of the hole in the crank and the end look pretty beat to hell...but it apparently is holding.

I can either assume all the pins are still in place and put the pan back on or should I drop the upper pans and explore more? I assume the oil pump must come off first?
 

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  • Ah! Schrodinger's plugs. You must assume that they are all in, and all out! Interesting.
  • Your right. There could be others missing that were never reinstalled, just removed from the pan. Unless you open Schrodinger's box you'll never be sure. That sucks more work less seat time.
 

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I'd pull the upper pan because, like I said earlier, it is not unusual for these engines to have scarily low oil pressure when hot, so you might want to pull a few rod caps and main caps and see what the bearings look like ... measure up and end up putting it all back together with no changes and learn to accept the oil pressure or put tape over your oil pressure gauge :)

OR you discover something that needs a repair ...
Pete
 
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