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The Making of Samson Worlds First V-12 107

119K views 184 replies 48 participants last post by  MBGraham  
#1 ·
It started out as a simple hypothetical question proposed on the internet in early 2006.

It turned into a personal challenge and an internet flame war. I think it was the phrase “lamest of all SL’s” that pissed me off.

Initial thread form another site where question was proposed:

Thread: Engine Swap Questions M120 into 380SL
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#17
03-21-2006, 09:44 PM

Roncallo
88Black560SL Join Date: Oct 2004
Location: CT
Posts: 1,371

Quote:
Originally Posted by duxthe1
Sorry but I don't have pictures of someone else's car. The area in question is near the idler arm, that I am sure of. And yes the 5.0 was offered but there was more room engineered into that area for those cars, which yours is not. I'm not trying to B/S you. I am a 10 yr M/B tech. On any given day i can be working on both 107's and V12 cars. Heck, there is a 380 SL in my shop sitting without an engine in it. I know exactly how much room you have. I also mentioned the idea around the shop (mercedes only independant) and everybody chuckled and then agreed, "no way in hhell"

I'm sorry that I'm the only voice of reason here but I am trying to tell you that you have no idea what it will take to put a m120 into a w107. I can promise you it will exceed any notion you have by an enormous percentage. As a rough guess I'd bet you'll have to re-engineer at least 50% if not 75% of the entire car. If it were even remotely feasible don't you think someone would have done it by now? Hell, I've seen V12's stuffed into a C-class but you're talking about a 6 figure price tag on the conversion. Are you really serious about dropping that kind of scratch on one of the lamest of all SL's?


My response
Sorry I dont mean to start a flame war here. But so far you have given me no useful information. If you want to help give me the number in inches or pounds that you feel is going to knock this project out of the realm of practicality. I have also worked on MB for 10 years from 1978 to 1988 so I have never seen an M120 engine except in pictures. I have done some challenging engine swaps including Chevy 350 into a Ferrari 308 GTS and Ford 302 into a Pinto. I have recently seen an article on the web of and M100 6.3 iron block engine installed into a 113 280SL. I'm sure that engine is much heavier than the M120 and the car is smaller than the 107. I am now an Aerospace engineer and quite well accustomed to such challenges. I also have a full machine shop at my house.

Numbers please, "no way in hhell" is not a number

John Roncallo

It became apparent that any real useful information would required the purchase of an SL600 and hands on evaluation.

A 1996 SL600 with 45,000 miles was purchased at an insurance auction. The SL600 engine is run for evaluation using a surrogate radiator. Engine measurements are taken, the situation is carefully evaluated. Conclusion was that the engine was in good shape and would fit. At this point the project is considered a go.
 

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#2 ·
Finding the car

In May of 2006 a tired but totally rust free “Sadie In Red” arrives from CA. Funny thing about this car was that I thought I was purchasing a totally rust free body with 200,000 mils and the rest would be junk. It turns out the car ran great and really only needed the interior restored.
 

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#4 ·
Restoration of the 86 560 SL

Since the car ran so well I was in one of those hesitation modes where, Do I really want to pull out a perfectly good running engine and transmission and make this swap. So while I pondered this I began the restoration of the car.

Starts with a new hood pad, followed by AC box and dash overhaul. then Seat and door panel re-upholstery and color change from Palomino to Black.
 

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#6 ·
The MB Fleet

So now I have 2 perfectly good 560SL's and a SL600 V12 donor car. The two 560SL's are on display as stock 560's for the last time at the Sikorsky 2006 Car Show.
 

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#7 ·
The V12 engine is removed and fitted to a spare sub frame I purchased, so that I wouldn't have to take the 560SL apart until I was ready.
 

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#10 ·
Years ago I took a struggling 1.6 i4 out of my Mazda Miata and installed a crate Ford 302. That car had it's challenges but I ended up with a very capable machine and was quite happy. This one is surely more intricate. I greatly admire this project and want to thank you for sharing it!

Matt
 
#11 ·
John, I hope you save every detail in your builder log because this is a project near and dear to my heart. I have a picture of this complete in a 107, and would some day love to do this myself. I have completed the suspension work on my SLC dream machine AKA 450SLC 5.0AMG Mampe/AMG which is a thread that was started by me back in February. The reason I bring this up is that after much time was spent gathering sprung and unsprung weights and motion ratio ect, ect for the engineering of the spring and shock package we lowered it 3.15 inches using 425 lb spring rate for the front and 600 lb spring rate for the rear, and you may need an upgrade in this area, if so, let me know and I will hook you up with this company. Tomson



 
#14 ·
Decision Time

So its January 2007. Up until now the 560SL has not been touched but the SL600 is without an engine and trans. All assessments are made and it appears that the engine will fit with a few concerns. Now its time to decide. Do I really want to dismantle a perfectly good 560SL.

It all starts out as. I would just take the engine out of the 560SL and lobe the V12 in to see how it really fits. With a few tweaks of my spare sub frame and about 2 or 3 in and out sessions of the M120 V12, the engine is finally sitting in a place where it becomes obvious that this engine will go. What I wasn't sure of was if I would be able to get it low enough so that the hood would not have to be modified. Keeping the hood stock was a major goal.

On Feb 10 2007 the M120 is crudely in place in the 107 for the first time.
 

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#15 ·
Modifying the Subframe

Perhaps the most difficult task was the next step, modifying the subframe for the M120 V12. The goal here was to use the SL600 engine mounts since they are tuned to this engine. The subframe had to have its main cross member cut out and a new platform for the R129 mounts had to be added.

Trial sizing was done by cutting out the 129 cross member and tack welding it into positions for testing before the final subframe mods were made.

The pictures tell the story.
 

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#16 ·
Forming the Subframe Top Plate

With the subframe cutout to clear the bottom of the M120 engine and the engine mounting surface position and dimensions defined, it was time to make the permanent mounting surface. Since the subframe main beam was thinned, to recover some of the strength I used a 3/16" thick top plate to replace the cut out ~0.90" formed top shell of the subframe. This top plate would have been a great application for 4130 steel, but since I had to weld to a mild steel subframe that was out.

The question was how the hell am I going to bend a 3/16" steel plate. I decided to try making a male an female die out of 2"x12" wood laminates bolted together. I actually didn't really think this was going to work. I figured it would just give me an idea of the magnitude of the task. I purchased a 30 ton press, jury rigged the tooling together and bent the 3/16" plate into a U shape.

By the end of May 2007 the top plate was formed and tack welded in place for some final fit checks.
 

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#17 ·
Addressing Clearance Issues

With the Top plate formed and tack welded in place we could get to work on some real fit checks and address clearance issues. This would take many months of engine removals and installations.
 

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#18 ·
Final Welding

With fit checks complete the subframe can be fully welded and additional supporting structure can be added. Its now 6/24/2007, a subframe that fits the M120 engine is now starting to take shape.
 

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#19 ·
6-24-2007 Fit Check Assesment

Fitting the engine after final weld of top plate and making final adjustments.
 

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#21 ·
6-30-07 subframe mods

Finishing up the front cross member. Measuring and documenting.
 

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#22 ·
Painting the Subframe

Painted using Eastwood Extreme Chassis Black. Its now 7-1-2007
 

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#23 ·
Do Over dident like the Compressor and Alternator Clearance

Ruined a good paint job. I decided to put in smaller urethane bushings up front with some home made mounting hardware. 7-29-2007
 

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#25 ·
Cleaning Parts Before Installation

The Pressure Washer
 

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#26 ·
Installing the Transmission Mount and Driveshaft

It just so happened that with the engine in position the drive shaft was the right length. Well almost the right length. You actually had to unbolt the diff and slide it back a little to get the pilot to clear. Then it bolted right up once you changed the transmission output flange from a 4 web to a 3 web used in the later 129's. Seams MB couldn't figure out if 3 or 4 webs were better. A little bit of playing around with the trans cross member and the trans was mounted.
 

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#27 ·
Alternator and Airpump Brakets

See title. Its now 8-12-2007
 

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#29 ·
Fuel Pump Installation

The M120 engine requires 1/2 the pressure of the 560SL's CIS system. I probably could have just used only 1 560SL pump, but I elected to mount the complete 129 system in place. Of course there is no accumulator so the line on the elbow gets squeezed off an soldered.
 

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