I first looked up the spec for tap of an M11. And though 1.5mm pitch spec is 9.5mm drill, 1.0mm pitch spec is for 10mm drill so if you could find 11-1.0 head bolts that should be a good mix other than: if you TTY you'll be pulling 25% harder on the head and the block if you don't TTY you are going to have less and more clamping force but I think you could figure out the correct lubricated torque to achieve a very similar to spec clamping force

TTY on 10.9 M10 is 6T. TTY on M11 is 7.5T.

Normal torque on M11-1.0 is 5T. You could achieve 6T with about 20% over torque without getting to yield. I wouldn't veto the idea but I wouldn't TTY M11 into an aluminum block. For a quick fix without doing timeserts I would definitely consider M11-1.0 bolts. The lower stress on the aluminum side from the substantially larger surface area may likely be all it takes.

Anybody do Mercedes and BMW work that knows if the M11 can take re-installation of M11 TTY without blowing out the aluminum block? That'd be your answer.

Both videos involve iron engine blocks...and the use of M11 studs or bolts in higher horsepower/race applications...

Very different circumstances to using (mercedes) M11 head bolts in a stock M54 application to fix an overheated aluminum engine on the cheap..

Apples to Oranges.

Good Research, thanks for sharing.

For anyone who hasn't done it , tightening head bolts on an M54 is a bit of a white-knuckle, stress-inducing affair.

first the E-torx sockets, extensions, breaker bar and/or torque wrench often don't grip the e-torx bolts, or transfer torque perfectly.

The torque sequence is 30 ft lbs, then 90 degrees and then another 90 degrees. The last 90 is when you pray things don't go snap...Oh and you do this 14 times.

This M11 stuff with (overheated/re-tapped) M54 aluminum threads doesn't leave a lot of room for error. I use a basic torque wrench and a paper dial gauge - yes I should upgrade. But If you strip one of the 14 threads, you'll wish you did use time-serts.

It is well known in bimmerforums E39 section for the last 10 yrs, ppl have used the Mercedes M11 head bolts in the M54 aluminum block w/o issues.

The videos I listed above are there to show the tools/techniques, whether it is M50, M52 (Iron Block) vs M54 (Aluminum).

The M11 idea is to get rid of the "middleman", which is Timesert.

Of course one can use Timesert too, but be careful drilling the holes larger to accept Timesert sleeve. There is not much room there.

Fair enough, I have been on Bimmerforums E39 a while..not as long as you..I'll go over and look at this issue there...My sense from the E46, E53, and E39 communities is that a lot more people reinstalling heads on M54's are using time-serts and M10's rather than using M11's, but I'll look.

You may consider time-serts "middlemen" but they are actually a solid product for long-term (if not permanent) thread repair- particularly in aluminum. Wide-spread use in a variety of automotive and aircraft applications with a lot of engineering and data behind it..

Not all that expensive...Inserts are about $2 ea., and the cheapest tool set is $35 or so..although that requires very careful drilling. The fool-proof M54 time-sert kits are pretty pricey, but trade frequently on Ebay. You could buy, use, then sell the time-sert 1090 jig for about $100 or so.

I see the timesert idea as like putting a threaded insert in wood or plastic to spread the load. It's way stronger than the 11mm solution but with the 11mm being stronger than the 10 in the first place you can have a stronger clamping force. What amazes me is that the aluminum block can take yield strength of an M10 bolt even once.

I wouldn't even try a second time and would definitely take the M10 or timesert path if ever need to remove a head from one of my54.

My program for bolts doesn't show a thread overlap for metric but it does for sae and 7/16 fine is nearly a perfect match for M11 course.

https://uploads.tapatalk-cdn.com/202...5a72882899.jpg

75% tap is 9.92 and 50% (thread engagement/overlap) is 10.32, this suggests over 50% thread engagement with 10mm drill size on 11mm bolt.

The only way these bolts even work once is how many threads engage. Steel needs 3-5 threads to hold the strength of the bolt, aluminum probably needs 12-15.

It's borderline at the limit but so is using the 10mm the first time!

I love outside the box solutions and somebody figuring out that M11 Mercedes head bolt can work on M54/2 head is genius even if not as reliable or repeatable like timesert.