Not having any experience with M6's, but having bought my first BMW, 1983 633csi, four years ago I wonder what I need to consider and look for when I go to check this M6 out? I am a little worried about cost of maintenance and repairs over the 635.
Qualified for CarFax $5000 Clean History Title Guarantee. Bought by current owner in 1992 with 29k miles.

1987 BMW M6
Currently has 54,000 miles.
Car is in very good condition both body and mechanics, second owner.
Due to timing chain failure, a new Metric Mechanic 3.7 motor was installed at 50,800 miles. I don't recall seeing any timing chain failure equaling new motors, especially at such low mileage from occasionally checking the 6 Series Forum. Is that a fluke or due to high rev's???
Balanced and blue printed, hi-flo head has been ported and polished, lightened flywheel and new torque clutch assembly, new hi-flo exhaust system, and Dinan chip, approximately 330 HP.
Korman Clubsport suspension including Bilstein Sport shocks, H&R springs, 19mm & 25mm adjustable Dinan sway bars, decamber plates and Dinan control arm bushings.
Approx: $20k

Thank you,

Andy

PS: Why is Kelley Blue Book so low, $9,625?
:95

Blue book is great if you're buying a Jeep Grand Cherokee or Honda Accord, but when it comes to special interest vehicles, the books don't have a clue.

Can't help with the rest as I'm going through the research and learning process on these cars myself, but I'd be doing the common-sense things like asking for proof of these mods and something to substantiate the estimated power output.

GreyGhost:

Hmmm ... That's an interesting dilemma. Do you know ... Is the motor that is in the M now ... the original block or is it a completely different one? If it's different ... PASS on it. You wanna an M that is as original as possible. That's just IMHO.

As far as the timing chain ... I've never heard of a broken chain requirring a new ... or should I say a different motor ... unless of course ... it snapped at 8000rpm and all hell broke loose.

Do you happen to know which motor is in the M car now ...
an M88 or is it a S38?

Checkout bmwregistry.com and read up about the M6 and
the M635CSI. It's very interesting how they developed and how they compare.

If it was me ... I'd probably wouldn't buy someone else's
"HotRod" unless I personally knew the shop and knew a lot more details. $20k plus/minus 10% is about right for a very clean and original '88-M6.

I hope all goes well for you and you get what you are looking for.