Another M12 Transmission Mount Hole Screw Up

[JJ 911SC]

While putting back the engine in the car 2 years ago, I discover yet another POs surprise...

The bolt for the transmission mount would not go through the new mount??? Take the screw and try it with the old mount no problem.

Don't tell me... Yes he screw up the M12 thread, so he re-tap it to 14 and drilled the mount center. Since I was already late getting the car on the road, I re-use the drilled mount.

Now that I got the engine out again, I would like to bring the whole back to 12mm.

So my question (finally) is there enough "metal" around the hole to install a big-sert?

The drilling would be slightly bigger then the 14M already there and the tap for the insert would be just over 16mm.

Also was the original bolt a M12 X 64 (without the point)? If so, only about 12mm actually goes in which seem a bit short. Can not find the length anywhere.

Thanks

[proffighter]

I have a bad Helicoil thread there (not angled correct), so I will use Big Sert as well.

Plenty of material there:



For Bolt length I can say, that about 1.5 times of the diameter is reached max possible force for threads, no need for more (if both are same material)

[JJ 911SC]

Originally Posted by proffighter

I have a bad Helicoil thread there (not angled correct), so I will use Big Sert as well.

Plenty of material there:



For Bolt length I can say, that about 1.5 times of the diameter is reached max possible force for threads, no need for more (if both are same material)

Roland,

Merci, using normal standard it would be 18mm of thread engagement. I start to wonder if the POs use the wrong bolt. The insert default length in the M12 x 1.5 is 16.2 mm kit.

Cheers

JJ

[proffighter]

16.2mm is fine. 18mm is just the max, not what's needed for every application.

Now as you have a bigger Diameter in the material and the Big sert, which can hold more than cheap steel too, limit of the connection is increased compared to the stock one (For this reason some connections are equiped with Helicoils or Timeserts from factory)