Stripped #5 Spark Plug - Looking for perspective

[OldRanger]

Food for thought. A reputable advisor thinks there is "some room for the Time-Sert".

(Again, I'm contingency planning. At the moment, the car is at a BMW dealership...I can only image what they will tell me. Towing destinations at 2:00am on a Saturday were limited)

[OldRanger]

Hi sapote,

Thank you for your ideas and questions. Time-Sert tools in the kit include a seat cutter, and the instructions have a step for using that seat cutter to cut a seat for the insert flange. I believe this accounts for keeping things flush and properly sealing.

Calcuating the insert length per the timesert website: "TIME-SERT measures Thread Reach from under the washer to the LAST thread. EXAMPLE IF YOU GET YOUR SPARK PLUG LENGTH FROM SPARKPLUGS.COM
and your plug reach is 19mm subtract 2.5mm for the washer which is 16.5mm" When I looked up detail on the NGK spark plug DCPR8EKP - I saw the reach was 19mm (or 3/4"). I'm not good at math, nor do I have an NGK plug handy, but I think that puts the insert about a mm too long.

I agree that there is very little space, and I"m concerned about that.

One more thing: I am looking into costs to install a refinished head as a result of all of this, but I feel like this might be a temporary solution.

[sapote]

Are you going to install the timesert raise above the original top surface or under cut the head and have the timesert shoulder flush to the head surface? If the timesert raises above the surface then the splark plug is not protruded into the chamber enough for proper combustion. Try to have the spark tip the same depth as stock.

timesert length 17.7mm is less than plug 3/4", not longer as you said unless I am missing something here.

The spark plug is the center and does not have much space from the valve seats, so after drilling the bad threads and tapping new threads, how much material remain from plug threads to the seats? Too little can lead to cracked head.

[OldRanger]

Hi Folks,
Our 2002 170K mile M3 blew a spark plug out of #5 cylinder on a highway trip last Friday. The week prior, engine codes on #6 indicated a misfire and the car was running poorly, so my son replaced the coil and plug in that cylinder and it resolved the code. At that time, he also noticed the #5 coil was loose and discolored but there were no codes on that cylinder. I was helping remotely, but over the phone I didn't have enough information to assess anything beyond a worn out coil. So...we didn't take action at that time on #5. That information is mostly irrelevant...but I put it in there in case any of you have a similar experience of the indication that a spark plug is about to 'blow'. Maybe save yourself an uplanned breakdown.

Note: a reputable shop had recently (6 months ago) done a valve adjustment. So a professional was involved in the most recent spark plug removal/install. So, let's not dwell on why this happened and how awful it is. We ahve two high-mileage E46 M3s and this one is destined for track use. I'm just going to look forward on this one and bit the bullet.

Here's my 'ask' to the community: I don't have a spare cylinder head to take measurements, so I'm hoping for some help with that and also some informed opinions and recommendations. Does anyone know if there is sufficient space to tap the spark plug hole with Time-Sert tool 4212E and install insert 42125? Is that the right tool and insert? The tool is an M12x1.25 and the insert is M12x1.25x17.5mm spark plug P/n 42125. Although that insert is a bit longer than the plug threads, it's the insert that Time-Sert recommends for an M12x1.25 "3/4" depth spark plug.

Has anyone ever heard of this being successfully done on an S54?

Thanks,
Andy