Window Shopper: BMW M6

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Written by David S. Wallens

From the Sept. 2016 issue

Posted in Buyer's Guides

The 1980s gave us some pretty cool sport coupes–cars worthy of chauffeuring around the era’s Wall Street wolves, “Miami Vice” villains and off-duty F1 stars. In addition to the usual suspects from Porsche, Mercedes-Benz and even Chevrolet, BMW offered that market the M6.

The M6 isn’t nervous like its smaller sibling, the track-tuned M3. While the M6 also has a successful motorsports heritage, on the road it’s a relaxed GT with that big twin-cam, inline-six providing turbine-smooth power.

Outward visibility is abundant. The front seats are supportive. The rears are tiny, we concede, but are still present. And you could reason that the generous trunk helps offsets things toward the practical.

Then there’s the shape: powerful and timeless, despite being built on a body shell dating back to the 1976 model year.

That E24 model 6 Series platform was already a few years old when the performance M6 variant first appeared. Europe got theirs starting in 1983, but American consumers had to wait until the 1987 model year. No matter the market, the recipe was similar: In addition to a boost in power and a Getrag fivespeed gearbox, the M6 received stiffer springs, shocks and anti-roll bars. A lowered ride height, trunk spoiler and deep front air dam were among the visual cues. Inside was wall-to-wall leather.

Michelin TRX tires came standard, and these didn’t follow the usual rim diameters; the M6 received a 240/45VR415 tire mounted on a 16.3x7.7-inch wheel. What does that mean? You’re going to have to seek a specialist for replacement rubber, assuming that the car is still wearing its stock wheels. Coker Tire can help, with fresh Michelins in the correct size retailing for about $450 each.

The M6 wasn’t a cheap date back then, either, carrying an MSRP approaching $60,000. Current prices have started to climb, too, with the best ones approaching $55,000. If you act quickly, the rank and file cars are still in the $15,000-$35,000 range.

Shopping Advice

Since the first roundel-badged cars first started appearing on U.S. soil, Korman Autoworks’s shop and racing team has been one of the most influential BMW motorsports ambassadors in t he country. Allen Patterson manages the shop and shares some shopping and ownership tips:

First-generation M6s carry the reputation of being “Bavarian Ferraris,” but if they are well maintained you can drive one daily.

If you’re shopping for one of these cars, do a compression and leakdown test. The main expense you will have will be under the hood. Well-maintained examples can go 200,000 miles or more, but that’s generally considered the end of the useful service life. Yes, there are higher-mileage examples, but you’re risking having to find a core engine in addition to a rebuild.

Good, used transmissions are almost impossible to find, and BMW doesn’t sell new or remanufactured units presently. If you do have a transmission problem, rebuilds are not cheap, but they are very robust boxes.

U.S. cars have dual air conditioning systems, which are prone to problems. Often the valve that splits the refrigerant between front and rear fails, leaving you with only one part working. The car needs both to keep you cool; that’s why BMW added the rear unit–and its accompanying beverage cooler.

U.S.-spec M6s rarely have rust issues unless the undercoating gets damaged–which can occur by jacking the car up.

Most U.S. cars have had the rear load-leveling suspension deleted by now in favor of the conventional 635i-type suspension. This is not going to bring down the value of the car much, but we often find that not all the components were removed in conversion. Do so for weight savings.

Steer clear of early M6s that had the M88 engine–shared with the E28 M5. These are all gray market cars and had to be federalized. U.S.-market cars had an S38 engine under the hood. We’ve yet to find any two M88 cars that were brought up to U.S. standards the same way. The problems with these are not with the body or lighting but with the piggyback oxygen sensor systems. The high compression combined with our fuel and these generic systems inevitably leads to detonation, which in turn breaks the piston ring lands. Even the best maintained cars eventually succumb to this.

The S38’s double-row timing chain is generally good for the life of the engine. We have converted M88s to double-row chains, but it’s expensive and not worth it.

It’s long been thought that the crank hubs on both the M88 and S38 engines were too soft and would eventually allow the crank nut to come loose, but we’ve never seen this happen when the crank nut was properly torqued.

S38s can utilize cams from the later S38B36 or Schrick camshafts, and there are various combinations of timing gears available to further tune the power band. Schrick cams work great but have a different base circle; getting them to work requires a combination of valve height adjustments and lash caps to bring things into the adjustment range. Your local machine shop is not the place for this unless they tell you about it first.

The headers from the M88 work nicely on the U.S. M6 (or M5) and provide some gains over the U.S. manifolds.

You may be tempted to do away with the vane-type airflow meter in favor of a MAF conversion. We have fixed cars by removing these conversions, but never by putting them on.

If you haven’t replaced all the rubber in the rear suspension, you need to.

Sway bars from the M5 are a nice upgrade, but aren’t a bolt-on upgrade in the front. The brackets have to be removed from the frame rails and new ones welded in place, but doing so allows you to use stock BMW parts. BMW no longer supplies the brackets, but we manufacture them.

This story ran in an old issue of Classic Motorsports. Want to make sure you’re reading all the latest stories? Subscribe now.

Resources

PARTS & SERVICE

Bavarian Autosport
(800) 535-2002
bavauto.com

BimmerHaus
(720) 566-0521
bimmerhaus.com

BimmerWorld
(877) 639-9648
bimmerworld.com

BMP Design
(800) 648-7278
bmpdesign.com

Korman Autoworks
(336) 275-1494
kormanautoworks.com

Pelican Parts
(888) 280-7799
pelicanparts.com

UUC Motorwerks
(678) 679-5360
uucmotorwerks.com

CLUBS & INFO

BMW Car Club of America
(800) 878-9292
bmwcca.org

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Reader comments:

wspohn
wspohn HalfDork
Oct. 14, 2016 9:43 a.m.

The first generation M6 was a bit ponderous and significantly slower then the first gen M3, but the engine is one of the best straight 6s ever built and sounds great.

M5 are a bit lighter but quite rare. The M3 (first iteration) are probably still the best bet for enthusiast owners. The E46 version starting in 2000 had the superb S54 engine with 333 bhp and an 8,000 rpm red line.

Mister Fister
Mister Fister New Reader
Oct. 14, 2016 1:27 p.m.

I have a friend with one who just throws money at it as if it were wood into a fire pit.

David S. Wallens
David S. Wallens Editorial Director
May 8, 2017 7:19 p.m.

Just a little update: Bonhams recently sold one of these for $104,500!

It was really clean, though:

Toebra
Toebra HalfDork
May 17, 2017 6:37 p.m.

There is one of those under a tarp on the side of a house I walk by every day with my dog. Also has a nice 911 longhood targa in the garage that is an all original gem. Always dug the M6, that BMW I-6 is smooth as silk

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