Double timing chains - what year did they make the switch?

[John Hubertz]

Does anyone know when Mercedes began installing double-row timing chains on the 4.5 V8?

[alabbasi]

Pretty much since the 4.5 has been around. My 73 has a double row chain. I think the only time they put a single row chain on a V8 since was on the 3.8 liter W116 engine, some of the experts will verify.

[oscar]

Since my '73 3.5l is an early model I assumed all these V8's had double chains.  Looking thru my Haynes manual, no mention is made of a single chain and indeed all photos are of double chains.

[Tomi]

All W116 cars have the double row cam chain, all V8's as well as the 280.

Only in years 81-83 the 380 had a single chain, but then its another chassis as the SL  107.

But I dont know anything about before the W116 era

[John Hubertz]

Thanks - that's a relief - I'd been shopping a 380SL and have seen so many broken 450 chains that I assumed the early 450s had single row chains.

[John Hubertz]

On a similar bent - it is my intention to quick-flush my new 450 with gunk engine flush, change the oil and simultaneously add a quart of slick-50 teflon anti-seize.

I know not to expose the engine to the flush for too long - something about rubber tubes in the oil flow to the heads....

Anybody have any precautions or details?

[michaeld]

John,
I can't speak for the motor flush time table, but I have an article that may interest you that talks about timing chains and whatnot.  I'll just copy and paste it right here (NO, I'm NOT being wordy here even for me!!!).  I'm sorry, but I didn't get the web address on this.


MERCEDES-BENZ 350 / 450 / 380 / 560 SLs
Status-symbol bargains for the not-so rich and famous
BY PETER BOHR
They called it der Panzerwagen. The "armored car", as it translated from  the Teutonic tongue, wouldn't seem to be a very dignified name for an automobile that's become one of the most coveted status symbols of our times. But those in Mercedes-Benz engineering who coined the moniker for the new 350SL had a point. Compared with the lovely, svelte 280SL that it was to replace, the 350SL did indeed look brutishly impregnable.
Of course, given the regulatory climate at the dawn of the Seventies, that was the point, Mercedes engineers knew the new design would have to meet not only the desires of consumers, but also the safety (and emissions) standards of U.S. lawmakers.
The 350SL ended up heavier and less efficient that the 280SL of the Sixties, far less sporting that the legendary 300SL of the fifties, and almost homely next to the two previous beauties. Yet the design worked-- so gloriously, in fact, that it persisted almost unchanged for nearly two decades, selling  about a quarter of a million copies along the way.
Unfortunately for poor but enthusiastic SL fanciers, prices also rose along the way, by about 500 percent -- from $10,500 in 1972 to $ 64,200 in 1989.
But now, for us less monied enthusiast, there's been a happy confluence of events  that has made owning an SL affordable. Thanks to the introduction of the current 300/500SL, the nation's sluggish economy and the vast numbers of these SLs on the market, you can put a fine example in your garage for a little as $12,000. Intrigued? Then read on.

SL foibles
In affluent Newport Beach California, home of R&T, residents drive "Newport-Beach-Chevys" elsewhere know as Mercedes-Benzes. And in the area around our offices, there seems to be a Mercedes mechanic on every block. Steve Marx, owner of Marx Mercedes Service, and Rod Curha, owner of  Dan's Automotive Service, are two of the most knowledgeable. We culled their wisdom regarding the purchase of an older SL. And we also turned to a nearby Costa Mesa resident for advise, Doug Rugg, proprietor of an independent  used Mercedes dealership, DR imports.
The well-heeled usually choose their status symbols for compelling reasons, and these SLs process a host of them. They were built with superb care. They show sophisticated engineering. They're sublimely comfortable. And because of their bulk and stout structures, they're just about the safest open cars  imaginable. But beyond these attributes, most of these 1972-1989 V-8-powered SLs have engines that are just about unburstable.
"I've driven a number of early 4.5-liter SLs with 750,000 or more on their engines," said Rugg. "At a million miles they get a little edgy". That may be stretching things just a bit, according to Cunha and Marx. But both agree the iron-block V-8s are exceptionally long-lived.  "Around 350,000 before a bottom-end overhaul isn't unrealistic," said Cunha. "The top end is often good for 180,000-240,000 miles."  And from Marx, "I have some customers with at least 300,000  miles on their cars and the engines haven't even needed valve jobs."
So does this mean a high-mileage early SL, say, one with 150,000 or even 200,000 miles, might still be a good buy? You bet. "I wouldn't be afraid of it, as long as I knew its service history and it was a good car in other respects," said Cunha. (All of our experts recommend oil changes be done  every 3000 miles.)
Still, all things being equal, it's best to avoid 1975-1976 models, and 1974 California cars as well. In the former, the cars carried catalytic converters inside the engine compartment. The heat generated by the converters tends to cook wiring and vacuum lines under the hood. Vapor lock was also a common malady. Mercedes engineers moved the catalysts farther downstream for 1977. The 1974 California cars, according to Marx, were equipped with exhaust-gas-recirculation devices that cause stumbling problems.
For model year 1981, Mercedes substituted a lighter, more efficient all-alloy 3.8  liter V-8 for the old reliable iron-block 4.5-liter V-8. And along with it came trouble.
The engine has a single-row timing chain, which as the miles piles on, tend to stretch. Unchecked, the chain can jump its sprockets, causing pistons to collide with valves, leaving the 380SL owner facing a $6,000 repair bill. During 1984, Mercedes switched to a double-row chain and solved the problem.
Though it was not an announced recall, Rugg says that at one time Mercedes did convert  some of the early 380SLs, free of charge, to double row chain for some customers. "The only way to know if a car is converted is to take off the valve cover and look."
Converting one now is a $2500-$3000 proposition, said Marx. But Marx added that the  conversion is unnecessary if the owner changes the chain and tensioner every 40,000 miles -- a $300 job.
Owners of 380Sls -- and later 560SLs, another SL with an all-alloy V-8 -- may also find that if their cylinders heads need to come off for any reason, they'll face an extra expense of several hundred dollars, in addition to a valve job or work needs to be done. Mercedes suggests that once the head bolts are removed, the aluminum block must be helicoiled to provide new threads. Otherwise, the bolts may pull out.
However, Marx said he's successfully replaced the head bolts on several 380 and 560  engines without helicoling. "You just have to torque them down very carefully, according to the book," he said. "But maybe I've just been lucky so far," he added.
Given regular service, the rest of the drivetrain, and most of the car for that  matter, seems to be nearly as robust as the engine. Our panel of experts report no unusual problems with automatic transmissions (manual gearboxes were never an option on U.S.-spec cars), rear ends, suspension or electrical components. Cunha said front brake rotors might need replacing every 40,000 miles, catalytic converters sometimes plug up after 100,000 miles, and water pumps, fan clutches and started may fail after 80,000 or 100,000 miles.
The 450SLs were subject to a formal recall, one still being honored by Mercedes-Benz, for cracking subframes. The dealer will replace or weld the subframe.
During the Seventies, German cars were not noted for their effective air conditioners, and these SLs are no exception. Except for the servo units in the automatic climate-control systems of the 1977-1980 450SLs, which seem to fail every three years, the air conditioners don't break particularly  often. "They just don't cool well", said Marx.
SLs aren't given to rust. But any prospective buyer of a car that's lived much of its life in an area where salt is used on winter roads should check the steel lid that covers the hardtop, the front fenders, around the headlights, inside the trunk and the rear box section of the chassis.
Paint, chrome and upholstery hold up well. Even the dashboards aren't prone to cracking, except blue ones for some reason. The horsehair seat padding, however, does tend to collapse over time. But replacement pads are available.
Indeed, Hemming Motor New is chock-full of advertisements for Mercedes or SL specialists who can provide almost any body, trim or mechanical item. Mercedes-Benz dealers can also supply most parts for these SLs.

PRODUCTION HISTORY
1971: V-8-powered 350SL 4.5 (body style "W107" in  Mercedes-Benz nomenclature) introduced to U.S. as as a 1972 model. Though introduced in Europe with a 3.5-liter engine, the W107 always carried a less efficient but detoxed 230-bhp, 4.5-liter, Iron-block V-8 here, coupled with a 3-speed automatic. Power-assisted steering, air conditioning, hard and soft-tops were standard.
1973: Name changed in American market to 450SL.
1974: Addition of 5-mph bumper. Horsepower declined to 190 bhp. California version acquired EGR and fuel injection.
1975: Addition of catalytic converters. Horsepower declined to 180 bhp.
1976 : Addition of cruise control, transistorized ignition, hydraulic valve adjusters; switch from Bosch electronic to Bosch Jetronic fuel injection.
1977: Catalytic convertors moved downstream. Climate-control system introduced.
1980: 3-way catalytic converter introduced, final drive ratio reduced. Horsepower declined to 160 bhp, but fuel economy increased.
1981: 380SL with 3.8 liter, 155 bhp, all-alloy V-8 and 4-speed automatic introduced to U.S. market. Electric window lifts are standard.
1983: Recalibrated engine and transmission for improved performance and fuel economy.
1984: Switch from single-row to twin-row timing chain.
1985: ABS became standard; driver-side airbag was optional.
1986: 560SL with with 5.6-litter, 227-bhp all-alloy V-8 and 4-speed  transmission into U.S. market. Limited-slip differential, front air dam,  leather upholstery, anti-theft alarm are standard.
1989: W107 production ended.

SL selection tips
Given the long model run and the various engine changes, there is a pecking order of desirability among the V-8 SLs. For guidance on this aspect of SL buying, we turned to John Olson, of the SL Market (2020 S. Girard, Minneapolis, Minn. 55405, $42 for nine issues).
Because it represents the pinnacle of the car's development, Olsin places the 560SL  at the top of his SL list. Of course, as relative youngsters, they also command the highest prices.  Next in line come the models that generally cost the least: The earliest V-8 SLs, the 1972-1973 models. Horsepower steadily declined in subsequent years, reaching a low with the 380SL. Moreover, these earliest car don't have catalytic converters to worry about, and they have the esthetic advantage of smaller European bumpers.
Third on Olson's list are the 1979-1980 450SLs, which represent the pinnacle of  development for the trusty 4.5-liter cars. All the other years would come next, except for the 1981-1983 380SLs with their cursed single-row timing chains. These 380SLs would be his last choice among the 1972-1989.

SL variants
Then there's the SLC, the stretched pillarless couple version of the SL. The extra 14 in. of wheelbase allowed for reasonably roomy rear seat. Introduced immediately after the SL, the limited-production SLC became the top of the Mercedes' model line (beside the very limited-production 600). Some called its  handling crisper than the SL's, while others appreciated the added carrying capacity. But perhaps because of Ho-hum looks and its fixed top, the SLC never became very popular here.  he model was discontinued after 1981.  Today SLCs can cost 10-20 percent less than the SL and, in this respect, represent quite a bargain.
Any SL shopper is likely to come across gray-market cars as well, cars originally  sold in Europe but supposedly brought into compliance with U.S. safety and emissions regulations. In Europe these SLs came with a bewildering array of engines and transmissions. Some, like the powerful 500SL, were very  desirable indeed. Olson estimated that during 1985 alone, the peak year for gray-market imports, some 5000 SLs entered the U.S. If you should seriously consider purchasing a gray-market car, check especially carefully for rust, and make certain the proper EPA and DOT releases come with the title.
And are any of these V-8-powered SLs likely to become valuable collectibles? You probably shouldn't plan to retire off the profits from one of these cars. Unlike their predecessors the 300SL or 230/250/280SL, the V-8 cars are just too numerous to become collector pieces any time soon. Instead, these are  cars to buy, use and enjoy.