Oil Tank drain plug

Sorry to hear of the troubles. I cannot help, but can the experts chime in on the best preventive measures? Should one apply anti-seize grease to the bolt before installation?

 

How on earth did someone damage the threads in the oil tank lower casting. It has a Heli-coil in it from the factory. Did they pull the Heli-coil insert out of the hole? The tap is a large special tap that may have to be purchased from Heli-coil. Measure the threads on the oil drain plug and just get a Helicoil kit for that size plug.

Your other option is to just replace the casting on the bottom of the oil tank. It comes with a new Heli-coil already installed and may save you a bunch of headache from trying to salvage your damaged casting. It only costs $122 from Ricambi and easily comes off with just four nuts.

 

How do you spell, "Torque Wrench"?

 

Mule head torque wrench!!

 

The dealership did not know that the drain has a helicoil in it? Ferrari has been using helicoils all of their oil drains since they came out with the 308GTB over 40 years ago! They even show the helicoil as a replacement part with its own part number in the factory Ferrari parts catalogues.

My guess is that there is not enough metal left in the casting to support a new helicoil if you were to tap the threads. The new helicoil would just pull out again when the drain plug was tightened. If the casting was unavailable or very expensive, then then I would have a machinist bore out the casting, and machine a threaded insert that would be welded into the casting. This is how we have oil sumps on early Ferrari 250GT engines repaired. The cost of this repair would exceed that of the new casting ($122) for your 612.

I would keep your old casting on my desk as a paperweight.

 

A Helicoil is not the only kind of thread insert available. Solid inserts are also available which are a solid piece of cylindrical material threaded on the inside and outside. Their wall thickness is greater than a Helicoil and hence the required tapped hole will be bigger allowing you a direct fix for the damaged Helicoil thread by simply drilling and tapping for the solid insert. Google “Metric Thread Inserts” and you should be able to find a suitable part to fix this problem.

The use of a torque wrench is not necessarily a prevention for thread damage such as this, in fact, it can be the cause of it. There is an expression “good hands” referring to a comptent mechanics ability to feel what is happening as a fastener is tightened. A good mechanic should be able to descern by feel if the fastener is snugging up properly or the threads are binding and about to do damage. Blindly relying on a torque wrench instead of experience and feel, particularly one that is physicaly large, is more likely to cause such damage than prevent it.

 

You need both, not just the hand feel part. Ferrari had "hand tighten" in the WSM for the oil filters in the 550, and that led to all kinds of blown filters. The 575M had a torque figure after they learned that lesson.

 

I believe Hill Engineering makes a replacement plate that replaces the entire drain plug, at least the did when I had my 360. Same problem with that car.