Repairing Stripped Threads for Oil Pan Bolts

During some periodic maintenance in the shop, the TR6 sump was finished up. The fasteners were all torqued to 20-foot pounds as stipulated in the manual. Of course, this is not done without risk. The fasteners are threaded into the steel block for the most part. Two of the bolts in front are threaded into an aluminum cap that fits under the crank shaft. Aluminum is not as strong as steel so the threads frequently get stripped out.

Fortunately, there is a fix for this, Heli coil inserts as seen on the tip of the black tool second from left in the picture.

If you use a long 21/64ths bit you don’t even have to remove the pan to make the fix. Pretty cool.

So, with a long drill bit, a Heli coil kit and the help of some 8-point sockets this job is easy and very effective as long as you can drill and tap a hole straight.

You simply drill the stripped-out hole to size to be tapped. Then tap the hole using the tap provided in the kit for the 5/16-24 UNF threaded insert. The kit tool is used to install the insert in the threaded hole. Then reinstall the original fastener.

The copper color around the bolt heads is a copper-based thread dressing

All bolts are now torqued properly so any seepage from the front is now doubtful. I may yet achieve a leak free TR6. Ok, stop laughing now.

Note! 8-point sockets are handy because as you will see, the thread tap and insert tool are square on the end. This type of socket is appropriate for square applications.

John Phillips


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