Hot Rod 6.9 - Mercedes-Benz Forum

LinkBack Thread Tools Display Modes
post #1 of 8 (permalink) Old 04-03-2007, 02:44 AM Thread Starter
BenzWorld Junior Member
Date registered: Apr 2007
Posts: 5
Mentioned: 0 Post(s)
Quoted: 0 Post(s)
(Thread Starter)
Hot Rod 6.9

Hello, I just joined this forum and I am very new to Mercedes Benz in general. I have allot of questions but I am mainly looking for where I can find more information in terms of resources and links.

Although I would also be very appreciative of direct answers, I realize I am probably asking novice questions that may be a waste of your time. Perhaps just shoot at some of the more technical stuff I ask that I may not be able to find with general resources.

I think a bit of an explanation is in order as to why I have suddenly become interested in MB (is this the common abbreviation?).

I am mostly a hot rodder. I like old muscle cars and big blocks and making things fast. I also like technology and discovering and investigating unique or complex mechanical devices, especially automotive. This is part of my blossoming interest in MB, they seem to have used allot of interesting technology in the older cars that I might be able to get at an affordable price now, so I can have fun and poke around inside.

One of my favorite movies is Lost Highway. For those of you that have seen the move I probably need not say more. But for those who have not, there is a certain car in the movie, a certain black Benz that is portrayed in a very spectacular manner. This car turns out to be a 450SEL 6.9. At one point the driver gets pretty angry and just before he hits the throttle says

“This is where mechanical excellence and one-thousand four-hundred horsepower pays off.”

I didn’t think much of it seeing the movie the first time and knowing a bit about cars and especially cars in movies at the time but the quote stuck with me. I know there are not many production engines that can handle that sort of output even when heavily modified and strengthened. When seeing the movie subsequent times I paid more attention to the car, there is one picture they show when the hood is opened that shows it is clearly turbocharged.

I did some research on the car and come to find out the thing actually sounds pretty hardcore. It is a 6.9 Liter engine. Which is right in the neighborhood of most big blocks of the 60’s. So I figure it has the displacement under high boost to hit that quoted hp #. Then I see it has all forged internals. This makes it much more plausible that this concept isn’t total rubbish. Next I read it has a stock dry sump oiling system. I will say this is what got me. I have not even heard of a stock production engine utilizing a dry sump system. Of course I have no idea how sophisticated it is but none the less this is damn impressive.

So then I think of cost and the usual rumors of how expensive it is to repair and maintain a Benz. The original cost of the car in the 70’s was upwards of 50 grand in the us. But when I poked around a bit I found a used one that looked to be in fair running condition for under 5 thousand on ebaymotors.

So the possibility of acquiring and building such a car does not seem nearly as far fetched as I would have thought.

Now for the questions.

How true are the rumors of the parts availability and cost of MB stuff, specifically in relation to this car?

Do most of the parts (not internals obviously) from other m-100 engines interchange with the 6.9?

Is the same true for the W116 car parts?

How popular or plentiful are parts cars for a W116 base and or remanufactured parts (basically not $ factory stuff)

Where can I find out more about repairing and modifying this car?

Is there any sort of fan base or fan sites specifically for this model?

Is there any aftermarket support for it, like manifolds or cams? Or is most everything a custom job when you modify it.

What is the real world potential of the 6.9 engine?

Can it actually handle 1400 hp on the stock bottom end? 1000 hp?

What is the main bearing configuration?

What is the bore spacing?

What is the stock redline and how far can it be pushed using the stock shortblock?

What is the cylinder head configuration?

I know it is overhead cam but are the valves inline or canted at all? I assume 2 valve.

Are there any known head flow values or popular porting techniques for them?

Are there aftermarket higher tension springs for bigger camshafts (if there are camshafts)?

How strong is the stock driveline? Trans, differential, axles?

Is there any aftermarket support for these parts as well or would they need to be replaced entirely to support such torque output?

What are your opinions on the hydropneumatic suspension?

Is this designed mostly for ride comfort or does it have improved handling characteristics as well?

Is there any kind of support or technical information about this system or would it be very difficult to service myself?

I found it very surprising that I couldn’t find more technical information about this car on the internet given it is said to have quite a reputation as one of the fastest 4 doors ever made. I am hoping that this is inaccurate and I simply was unable to find these resources and that they do in fact exist and maybe some people on here would know about them.

Lastly, does anyone own one of these cars? Any fun subjective descriptions or anecdotes to feed my growing desire to drive one?

Sorry for the novel here I simply wanted to explain who I am and what my intentions are in being here and asking your help. If I do go through with this all I will take allot of pictures and compile as much detailed information on the project as I can to share with you all. I will probably make a website chronicling the build for those who might be interested.

Thanks for taking time to read this all and double thanks if you choose to take more time to respond with any helpful information.

Tim Iacobucci
TimIacobucci is offline  
Sponsored Links
post #2 of 8 (permalink) Old 04-03-2007, 05:26 AM Thread Starter
BenzWorld Junior Member
Date registered: Apr 2007
Posts: 5
Mentioned: 0 Post(s)
Quoted: 0 Post(s)
(Thread Starter)
In doing more searching I have already answered a few of my own questions.

mercedes 450 SEL 6.9 history

This website proved very informative about the suspension and engine.

The engine block extends down well beyond the center line of the five-mainbearing crankshaft, and the center three main bearing caps are cross-bolted in racing-engine style. Thrust is taken by the center main.
Man the more details I hear the better it gets. Cross bolted mains, forged crank and rods, dry sump oiling. This thing may actually handle 1000+ ft/lbs without a problem. Why have I never heard of this before?


The car is so responsive and controllable that one is probably in danger of becoming wildly overconfident."

"There are no springs or shock absorbers per se in the 6.9 suspension. Both functions have been combined into a single hydraulic strut that mounts in place of the coil spring and shock absorber at each wheel. The telescoping struts support the car with oil pressure generated by a small radial piston pump on the engine. A separate bell-shaped pressure reservoir, connected to each strut by a high-pressure hose, contains a permanently sealed charge of nitrogen gas that functions as a spring. Working pressures in the system range from 2100 to 2900 psi. "

"When the 6.9 hits a bump in the road, the wheel rises and telescopes its suspension strut. Oil forced out of the strut passes through the hose to the reservoir, where it acts on a diaphragm and compresses the gas. The gas behaves like a progressive spring. The more it's compressed, the harder it is to compress further. In other words, the suspension rates change in direct proportion to the load. Thus the rates can be relatively soft without fear that the suspension will bottom out easily. The same softness, combined with the fully independent suspension, allows each tire to stay on the road surface even over very rough sections. To compensate for the higher degree of roll that would otherwise be encountered during cornering with the lower spring rates, the front and rear stabilizer bars of the 6.9 are stiffer than on the 450SEL. "

"Because the gas charge is fixed, the amount of oil in the system determines the ride height. Automatic regulator valves adjust oil volume constantly to compensate for vehicle load. Thus leveling takes place independently and automatically at both front and rear.

Due to inclusion of a separate pressure reservoir for the system as a whole, this occurs even when the engine isn't running. "

"Front and rear level-control valves use the center of the respective stabilizer bar as a reference point. A lever connected to each bar responds to the average position of the body of the vehicle relative to the axle. When a level-control valve is actuated, additional hydraulic oil is then forced into both struts on the appropriate axle. "

"The front suspension and steering geometry of the 6.9 are basically the same as on the Mercedes 450SEL, but several components have been changed to accommodate the mounting of the hydraulic struts rather than conventional springs. The steering linkage has been strengthened to account for the increased vehicle weight and larger tires of the 6.9.

The anti-dive feature of the W116 front suspension is particularly important with the hydropneumatic suspension due to the relatively soft springing."

"The inherent anti-squat characteristic of the 450SEL's semi-trailing-arm independent rear suspension has been supplemented on the 6.9 by the addition of a Watts linkage. Each rear wheel bearing is housed in a vertical carrier positioned between the light-alloy semi-trailing arm at the bottom and the lever arm of the rear stabilizer bar at the top. The brake caliper mounts on a second carrier, which also pivots around the axle halfshaft, but is horizontal and linked to a rearward extension of the semi-trailing arm by a steel plate. The position of the trailing arm relative to the stabilizer bar suppresses the tendency of the rear of the car to squat on acceleration. Similarly, these two elements, plus the pivoting brake caliper, reduce rear-end lift on hard braking."
The complexity and inherent maintenance headaches would probably seem daunting and I know I will curse myself at times but I think it just sounds intriguing. If I was to meet someone with this car I would in all likelihood climb under the car right there and then just to see how this stuff is laid out and what it looks like.

Again with the watts link, I think this is the first I have heard of a production car using this system. Too cool.
TimIacobucci is offline  
post #3 of 8 (permalink) Old 04-03-2007, 01:49 PM
Boring Cars...meh!
Nutz 4 Benz's Avatar
Date registered: Aug 2005
Vehicle: 81 280E, 84 500SEC, 87 560, 89 "300E", 91 500SL, 15 E350 4Matic Estate, 71 BMW 2002, +others
Location: Maui
Posts: 15,944
Mentioned: 0 Post(s)
Quoted: 16 Post(s)
Lifetime Premium Member
The engine in that 6.9 your are talking about from the movie in fact has an American 351 Cleveland V8 engine from a Ford,built up with a twin turbo setup ...... blasphemous,I know.

Another member here supercharged his 6.9 with a twinscrew and achieved like 900hp so don't lose faith
Nutz 4 Benz is offline  
post #4 of 8 (permalink) Old 04-03-2007, 03:13 PM
BenzWorld Elite
diametricalbenz's Avatar
Date registered: Oct 2005
Vehicle: '77 6.9, 74 240D, 96 Ram 5.9L Cummins, 02 Civic EX, 10 Mazda 5 Sport
Location: Atlanta, GA
Posts: 2,652
Mentioned: 0 Post(s)
Quoted: 3 Post(s)
That supercharged 6.9 ran him $20,000 or so as I recall unless the Kroner? exchange rate has changed significantly. It would be safe to say that the engine was not designed for 5 times the output but I guess anything is possible....for a short period of time. I love Lost Highway too and love playing that scene with the bodyguards with their seatbelts! I have yet to find what road that is on. I guess it's somewhere near Mullholland Dr. or somewhere in the Hollywood hills. I want to take my 6.9 on the road too and look for Ford Thunderbirds.

I guess David Lynch and John Frankenheimer liked the 6.9's so much they featured them in both movies.

Perhaps finding a 450SE/L with a blown motor and dropping in a Turbo V-8 might be more practical and probably a lot lighter too. The M-100 motor weighs 1000lbs alone.

1977 - W116 - 6.9
1974 - W115 - 240D /8 - 4(M) OM617.910 + Turbo + 300D FW - Completed 7/8/10
diametricalbenz is offline  
post #5 of 8 (permalink) Old 04-03-2007, 03:34 PM
BenzWorld Member
Date registered: Mar 2007
Posts: 91
Mentioned: 0 Post(s)
Quoted: 0 Post(s)
As a mechanical engineer and former auto mechanic, I share your interest in unusual technology, especially stuff that was so far ahead of its time. Unfortunately I have a different view on what you are proposing for the 6.9.

IMO, Mercedes Benz cars of that vintage were remarkable as much for their overall balance and poise as for anything else. They just drove astonishingly well for their size and weight. I know there are a lot of folks on this forum that modify their Benzes, and I hope they are happy with them. Personally, I have yet to enjoy driving a Benz with anything more than the most mild of modifications. I think there are plenty of other cars that lend themselves to all sorts of hot rodding. I think a classic 6.9 would be far better enjoyed for the remarkable machine it already is. Modern tires, not too radical though, perhaps upgraded brakes, and changing any engine components that were detuned from European specs for US emissions... that would be about the extent of my changes. The Mercedes engineers knew how to design a car as an integrated system, and radically altering the engine power, for example, would destroy that finely tuned integration in my opinion.
Jon L is offline  
post #6 of 8 (permalink) Old 04-04-2007, 03:14 AM Thread Starter
BenzWorld Junior Member
Date registered: Apr 2007
Posts: 5
Mentioned: 0 Post(s)
Quoted: 0 Post(s)
(Thread Starter)
To be honest my favorite engine is the ford 385 series big block. That’s the boss 429 version that came right at the end of the muscle car era after the 427 big block or FE engines. It is basically a canted valve Cleveland on steroids. I could build a 900 hp naturally aspirated version of this engine for a good amount less than 20K and put it in a Benz.

Damn a turbo Cleveland, honestly that news does taint the scene from Lost Highway a bit for me now though. I mean I have to wonder what mechanical excellence is he referring to? Is it the Benz or the Ford engine in it? Come on now.

Well my point is that there are allot of other Ford cars I could put a hot rod Ford engine into. I’m not even purposing that I want a 1400hp 6.9 to drive around. I was just wondering how capable it is. Technically it sounds damn stout. Quality forged bottom end components and block strength (cross bolted mains) are the first line of business for building an engine to handle high output. The 6.9 sounds like a much better base than a Cleveland to be honest with you. And this is coming from a longtime Ford lover.

Perhaps finding a 450SE/L with a blown motor and dropping in a Turbo V-8 might be more practical and probably a lot lighter too. The M-100 motor weighs 1000lbs alone.
Not many big blocks are gonna weigh much less. The more I talk about these 2 engines like they are separate the more I tend to think, well you know the m-100 really IS a big block isn’t it? Any word on the bore spacing?

Also the weight of the engine further testifies to me that it is probably very strong. More beef in the iron block and internals.

The Mercedes engineers knew how to design a car as an integrated system, and radically altering the engine power, for example, would destroy that finely tuned integration in my opinion.
I do definitely see what you are saying. And before I can really decide how much I agree with this or not I need to actually get one and drive around in it first. Maybe I will love it and never want for more. But being human and a rodder at that, I know I will most likely acclimate to the stock acceleration and want to tinker.

Also a turbo system, not a crazy all out race engine, but one that is designed specifically to do so, can feel and sound and behave just the same as stock off boost. It is really only there when you want it (full throttle). And honestly if this car is as quick as so many people have said you really can’t even get on the throttle that hard on the street more than a very tiny bit as it is, with any amount of safety anyways. I live in Orlando and allot of people, especially ricers and crotch rockets don’t seem to understand that rush hour traffic on the interstate is not an appropriate time for WOT.

But what I am saying is that the finely tuned integration you speak of could be maintained for 99 percent of the car’s intended usage.

Does anyone have any input as far as the technical questions I had about the car or better resources?

Does anyone know how much of the information I am looking for is covered in the factory manuals and literature?

And even aside from the hot rod aspect, how practical is it to think that I can repair and maintain this car myself? Any MB mechanics out there? Is the information available to service and rebuild components on this car without resorting to high price replacement parts from the factory?

I see that most people take their cars to a MB dealer or MB specialist. Which is understandable considering the complexity of some of the systems on these cars. But I like to delve into and study complex systems and I don’t mind getting my hands dirty but I do need the relevant information to do a proper job of it.
TimIacobucci is offline  
post #7 of 8 (permalink) Old 04-04-2007, 07:55 AM
BenzWorld Member
Date registered: Mar 2007
Posts: 91
Mentioned: 0 Post(s)
Quoted: 0 Post(s)
I think a nicely designed turbo system might be OK, or even a low boost supercharger setup with a bypass like an Eaton system. The nice thing about the supercharger with bypass is that it is really not there at all until you give it close to WOT, and then it is RIGHT THERE, even right off idle. It comes on very linearly. I doubt you really need much more top speed in a 6.9, and a supercharger will give you the acceleration. (I wouldn't need any more acceleration, either -- but then again I drive a diesel!). I think it might be hard to put together a turbo system that didn't have too much lag and then come on way too strong. As I recall there is not much room under the hood on a 6.9 to shoehorn in one or two turbos, and then there is the heat to deal with...

It's been a very long time, but I have worked on and driven 6.9's, 300SEL 6.3's, even a couple of 600 Limo's with the 6.3 engine. (The 600 had hydraulic power windows... holy crap, they were like silent guillotines! Push the button, the window silently and VERY quickly slid closed with so much feeling of power that it seemed like it could chop your hand off without slowing down.) IMO, it is very important to use meticulous practices on these cars. Read the manual for instructions on the factory repair methods before delving in. Use the factory instructions for reference before deciding if any shortcuts are appropriate. Don't screw up, because it will be expensive!
Jon L is offline  
post #8 of 8 (permalink) Old 04-04-2007, 04:29 PM
BenzWorld Member
mybenz123's Avatar
Date registered: May 2006
Vehicle: w123 300tdt
Location: Belleville, NJ
Posts: 362
Mentioned: 0 Post(s)
Quoted: 0 Post(s)
This might help.

Das grosse Portal fuer Mercedes M-100
James' Mercedes Benz 6.9 Page
The International M-100 Group

Last edited by mybenz123; 04-04-2007 at 04:35 PM.
mybenz123 is offline  
Sponsored Links

  Mercedes-Benz Forum > General Mercedes-Benz Forums > General Mercedes-Benz

Quick Reply

Register Now

In order to be able to post messages on the Mercedes-Benz Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Please enter a password for your user account. Note that passwords are case-sensitive.


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:


  • Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
    Thread Tools
    Show Printable Version Show Printable Version
    Email this Page Email this Page
    Display Modes
    Linear Mode Linear Mode

    Similar Threads
    Topic Author Forum Replies Last Post
    Mom's hot rod! '97 C36 roncor W202 C36 AMG, C43 AMG 1 10-24-2005 10:01 AM
    Hot rod lesco51 W123 E,CE,D,CD,TD,TE Class 9 08-04-2005 07:17 AM
    What would the "ultimate Mercedes hot-rod" be? Geeky1 General Mercedes-Benz 12 01-25-2005 06:26 AM
    Guess nobody wanted our Hot Rod dennisB W126 S,SE,SEC,SEL,SD,SDL Class 2 09-26-2004 11:12 AM
    american hot-rod zaystev W126 S,SE,SEC,SEL,SD,SDL Class 18 07-11-2004 11:41 AM

    Posting Rules  
    You may post new threads
    You may post replies
    You may not post attachments
    You may not edit your posts

    BB code is On
    Smilies are On
    [IMG] code is On
    HTML code is Off
    Trackbacks are On
    Pingbacks are On
    Refbacks are On


    Title goes here

    video goes here
    description goes here. Read Full Story
    For the best viewing experience please update your browser to Google Chrome