I will have some time here and there over the next month or so to make an adaptor plate to mate a 420G 6-speed to the M117 and M119 block.

Will be using the BMW ring gear so the starter will bolt up to the trans like it is supposed to. Once the trans is mounted to the block, the flywheel can be designed..

That is good news. Thanks David. -CTH

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It looks like a 1/4 or 3/8 thick adaptor plate would work to mate the 420G to the M119 block. A 1/4 inch thick adaptor would have to be steel and a 3/8 plate could be aluminum but would need a pocket machined into it for the fly wheel. Personally I prefer the thicker plate as there would be more thread engagement.

There are a couple of things that need to be addressed;

The MB ring gear is smaller than the BMW ring gear by a few teeth, so in order to use the starter mounting holes in the trans, a BMW ring gear will need to be used. I want to know how many teeth are on the BMW starter pinion. If it is the same as the MB pinion, then I can use the MB starter I have for a mock up, if not, then I will need to get a BMW starter.

The 420G does not complement the M119 crank position sensor location at all. I think the easiest thing to do would be to move it to the top of the trans and re-index the flywheel to compensate for the new location. I have no idea if there is room in the car for the sensor on the top of the trans though. Another alternative would be to see if a shorter pick up could be sourced that could fit inside the bell housing.

Re: Adapter Plate Thickness

If the M119 has a rear main seal holder similar to the M116/117 engines, the rear face of the crank flange (the flywheel surface) is approx. 20-22 mm behind the rear face of the block. A 3/8" thick plate (9.5mm) would be well forward of the flange/flywheel line. Is the anticipated flywheel stepped forward? Most flywheels have either a flat forward face, or are stepped aft.

The 1/4 inch min thickness for the plate results in the start of the input shaft spines section being .125 from the face of the pilot bearing if it were flush with the face of the crank, which leaves aprox .875 of input shaft pilot bearing depth in the crank. Keeping in mind that a pilot bearing adaptor can be made to put the bearing anywhere, the additional .125 of plate thickness (to get 3/8) is not a big deal, but the plate will need to be machined to allow the back of the flywheel room.

The back of the flywheel will be the same as the MB flex plate and will protrude out to the clutch disk. I will have to check on some mass specks in order to see where the flywheel total mass number should be. If the total mass is too high, then I will remove some material from the back of the flywheel to reduce weight, but I am thinking that thicker is what it will have to be, and that may require the trans to be set back by its self.

CTH has some 117 flywheels so we should have an idea of mass to start with.

Does that answer your concern?

"Does that answer your concern?"

Actually, no! I'm a bit puzzled.

My comment was directed to your suggestion that a plate of 3/8" thickness would interfere with the front side of the flywheel. If the forward plane of the flywheel is in line with the back face of the crank flange, it will be approx. 20-22mm aft of the back of the block. If the adapter plate, bolted to the back of the block is 9.5mm thick, there will be a clearance of 11.5-13.5mm between the aft face of the plate and the forward plane of the flywheel. What machining of the plate would be required for flywheel clearance when a clearance already exists?

Perhaps there is also a bit of confusion in terminology. I'm using fore and aft to refer to the front of the engine (and vehicle) and the back of the engine, and to all other components as well, when installed. Hence, the front of the flywheel is that side that faces forward in the vehicle, and is closest to the back of the engine block.

The v12 wasn't on my plate because I don't own one. My goal is to construct a custom engine adapter that has either a bmw, Chevy or ford bell pattern. That makes things very simple. An equally simple custom flywheel that has would take a corresponding off the shelf clutch.

A custom bell is not necessary nor is it very interesting. For the m100 and m119, thereally is plenty of work to do to get a reasonable flywheel together that can handle the three variety of the ignition timing hardware required. Going with the bell from a getrag 265 or s420 means a small flywheel like Dave said and it means beefing up the clutch. Thankfully that is easy (one you have a flywheel).

Current status is that we know what not to do and we know who's going to make the flywheel. I need to get them some measurements, they need to give me a quote, and then it's a matter of cutting them a check.

-cth

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I did read that you had a change of email address, but I had assumed that it was corrected. The email was not super important, it was just explaining my desires as to what I was looking for.

CTH did in fact email me about this, encouraging me not to simply wash my hands of it.

I do prefer the simplicity of a mid-plate rather than a total custom bell housing if I am going to attempt things. I had thought that this was going to be a case of using a bell that someone else had done the majority of the measuring and the actual production, just kick in some sample parts and a wad of cash. It was appealing to hear about a custom cast bell. If I have to go the route of the mid-plate I only need someone to measure it for me as I can have it laser cut from a CAD drawing. I do not trust myself to measure it right, though. This might mean bringing my extra motor to Minneapolis, as no one here seems to be able to run a CMM. First I am trying to get an in-law to do it, though. He is a mechanical draftsman.

I have not compared the bell patterns, but from what I read earlier in this thread the M119 is different from the M120, but the M113 might be the same as the M120. The conversation had dropped off after a maybe.

I am not super concerned with a clutch. If I have to go to something a little more aggressive, so be it - but I doubt I will. I think that the clutch will do better than most people think. Plus if I cook it, I can upgrade. There is that small matter of resurfacing a new flywheel...

I imagine that I will eventually pick up a bell for the T56 and make a mid-plate. If I go this route, I will cut out several so that I can help out some others and have a spare or three. After all, if it all goes well, I may do this more than once.

That would be good, I have no problem with piggy-backing on someone else's flywheel order. Was everyone thinking of using the factory MB ring gear, getting teeth cut into the new flywheel, or something else? I was thinking of using the factory MB ring gear bolted to a new center.
The later (722.6?) transmission had a removable converter housing, but I have the earlier (722.3?) transmission with the integral case. I will likely use a GM bell on the T56 and a mid-plate from engine to GM bell.
I plan on using a hydraulic throw-out.

Yes, I think that the GM bell for the Tremec makes more sense than the MB bell does at this point. Bonus - they are easier for me to get!

I do not blame you for not taking a large interest in something that in no way helps you - I am not enthusiastic about old Chevrolet small blocks for the same reason. Don't have one, don't care.
In theory I like offering options to people for the transmissions, but I would not do terribly out of my way to make that happen. If I wind up doing this for me I will offer it to other people as "take it or leave it". I cannot imagine using a BMW transmission, but maybe elsewhere they are easy to get.
I will watch for the flywheel information, though.

Like I said before, I wish you all luck. I think when it comes down to it I will be going on my own for this one, though. I hope if I am successful some other people appreciate my efforts and do the same combination.

Keep on keeping on, everyone!

With all the bell housing gyrations going around in this and other threads, has anyone investigated redrilling a drawn steel "blow proof" housing? There has to be one that has the front to rear correct spacing to make it work.

The MB pattern could be drilled on the outer flange, if any bolts are inside the flange, a tube could be welded through the bell to allow attachment.

Going farther, an aftermarket flywheel maker should be able to drill a FW to a MB pattern.

I'm thinking modify aftermarket parts rather than modifying / adapting MB to fit aftermarket parts.

an aftermarket flywheel maker is exactly the guys I'm talking with actually. I wasn't looking at the blow proof bells, presuming a factory one is good enough. Drilling an adapter plate is probably easier than modifying one of those bells given modern CNC techniques. But I don't have one of them handy to back up what I just said with facts. -CTH

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An aluminum factory bell on a stock street car is good enough from a scatter standpoint but not so easily modified.

The steel bell will have a more or less round flange ID and a irregular OD. The trick would be to find a ID that matches the smallest portion of the MB pattern while still clearing the clutch.

Redrilling the steel bell would be easier than making a plate with bolts going in two directions and you only have to drill one new pattern. ( An exception would be a motor that uses a steel plate from factory or when spacing the trans out is needed to make a flywheel work. )

Interesting idea. I will have to ask the clutch guy if he has a scatter shield handy. Thx -cth

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I considered using my aftermarket SFI rated bell housing that I purchased before deciding to use a V12, but it still has value, if not for the same project. I see no reason to destroy the SFI rating of a perfectly good and useable adapter bell that I paid $600 for to make this work. That's assuming that it would even clear the exhaust for the V12, in my case.
I don't know for other people, but I can find OEM parts to modify for much cheaper than AMP. Plus, the SFI rating is out the window the second it is modified (if anyone cares).
Now if someone had a junk old steel bell housing from a retired racecar or something, that would be a whole different story.

Depending on how things pan out (I am chasing a few different directions right now) I am leaning toward a mid-plate on a GM/Viper T56 bell, personally.
I think that this is something that is enough out of everyone's normal range of work and potentially problematic enough to scare people. It is going a new route no matter how one looks at it.

Anyone scared by this type of trailblazing is welcome to go buy a Chevrolet. Just do not expect it to be a car you love or your neighbor compliments.

A t56 or a tko or a magnum are all good options. The arguments for and against are based on cost vs reliability, gear ratios available, feel of the ride and will it fit in the car w/o taking a hammer to the tunnel.

I like the getrag s420 6 speed for its elan and the fact that I have one in good shape. It will be tossed when it needs a rebuild because that isn't at all a cost-effective move. But until then I will enjoy it.

All of the above transmissions will work with what's being done here.

On the M120 front, a quick web search for "mercedes m120 flywheel" turned up a picture of the crank bolt pattern. The location of the dowl is different to the M119. Knowing things like that up front helps.

-cth

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If you are running on the street, SFI isn't a consideration. I doubt that even lower level road race cars require SFI. In any event a ballistic blanket could be wrapped around the BH.

Quicktime makes a ton of different housings, I'd think they would be able to make a MB one if provided with dimensions.

Quick Time Bellhousings - Free Shipping on All Orders @ JEGS



A run of the mill Chevy blow proof is sub $ 400, used it should be in the sub $ 150 range.

Lakewood Blowproof Bellhousings - Free Shipping on All Orders @ JEGS

lakewoodindustries.com/

McLeod Standard SFI Bellhousings - Free Shipping on All Orders @ JEGS



The modular approach looks interesting and is a source for spacer rings though BH prices vary wildly.

McLeod Modular SFI Bellhousings - Free Shipping on All Orders @ JEGS



I did see someone fabricate a BH from steel, this could work if the finished product was final machined after welding.