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  #1  
Old 10-15-2018, 07:22 PM
ttownthomas
 
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Location: Cary NC
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Researching naturally aspirated performance M103's. Looking for facts (or rumors)

Disclaimer: I am considering attempting to rebuild/recreate a performance M103. I want to do it because I like to learn and not because I think it will be a good financial investment. I know I will loose money. I know i could buy a faster car and not go through all this trouble but what fun is that. I have also thought about doing a turbo build instead because I know I probably can't even get to 250 horsepower out of a naturally aspirated 3.2ish liter m103. Hopefully this disclaimer will defray some of the "this is stupid" commentary. I know its stupid.

With that being said: I am looking for information about performance M103's.

Here is what I think I have picked up so far about the AMG 3.2:

-The M103 2.6 is the base engine for the AMG 3.2 engine. (same bore as the 3.0)
-It may have been stroked by using the crank from a MB 3.5 Diesel (OM603)
Question:By my math that would give it 3100cc's so that crank "fact" may be a rumor.
-It had lightweight pistons and a proprietary AMG cam.
-I am assuming that it had the head ported and had different valve springs and probably lightened rockers.

Was there a 3.4 AMG m103?

I think there was a 3.0 AMG too?

I also know Brabus made a bored and stroked 3.6 that has a reputation for eating head gaskets.

Are there modern grinds available or shops in the USA that know how to work these engines?

Last edited by ttownthomas; 10-15-2018 at 08:21 PM.
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  #2  
Old 10-15-2018, 10:08 PM
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ITs STUPID.
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  #3  
Old 10-15-2018, 10:11 PM
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Had to get that out there as quick as possible.
Dont over bore it for the .1liter. The 3.5 crank or just get a 3.6 crank and go for high compression pistons. The cam you can have profiled and welded up and ground from a company like WEB CAMs. There is nothing super special about the engine. Any good machine shop could guide you. Leave springs and rockers alone most likely. They are going to have a pretty good spring rate. The only reason would be to get better lift before bind.
Biggest problem is getting air in and out of the engine. The CIS is a terrible restriction and then exhaust. The intake probably is pretty good.
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  #4  
Old 10-16-2018, 07:44 AM
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Our guy would be much better off going with a 4 valve M104 3.2 as this is more or less a bolt in swap.
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  #5  
Old 10-16-2018, 08:47 AM
ttownthomas
 
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I have done an engine swap (LS into a volvo 240 in my home garage). Truly part of this is to rebuild the motor because that is something I have not done. Depending on how much of a direct swap the M104 is I guess I would consider a performance home-built M104 and a swap. Is the cooling system capacity of the W126 sufficient for the M104?

If i do the M103 I do not plan to bore it.
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  #6  
Old 10-16-2018, 09:29 AM
ttownthomas
 
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Quote:
Originally Posted by whipplem104 View Post
Had to get that out there as quick as possible.
Dont over bore it for the .1liter. The 3.5 crank or just get a 3.6 crank
Which 3.6 engine has a crank that fits?
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  #7  
Old 10-16-2018, 12:32 PM
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the 3.6 he is referring to it the AMG c36 m104. it uses a modified OM603 3.5L crank with a stroke of 92.4mm. with the stock bore of a 103 it will get you around 3.5L the c36 is also bored out slightly to get 3.6 however this makes the head gasket a very short lived thing. i would seriously consider a 104 over a 103 due to the much better head flows of a 4 valve engine. that being said, as you stated this is just for the hell of it to see what can be done. for cams i would look at Dbilas Dynamic and Cat Cams they both stock grinds for 104's and 103's from mild to extreme. if you want to go all out start thinking of things like long tube equal length stepped bore headers, and ITB's. it all comes down to getting air in and out of the engine as fast and easily as possible.
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  #8  
Old 10-16-2018, 12:48 PM
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The M103 and M104 blocks only have detail differences that won't affect you if you use it as a complete long block. The oil pan won't interchange between the two due to the M104 using a double row timing chain. There are 2 M104 oil pans so select the one with a sump position that matches your car.

The best year in terms of FI system will be a Bosch ME 2.0 / ME 2.1 ( 97 C280 / 97 E320 / 97 SL320 / 97 -99 S320 ) as this has drive by wire not the troublesome half cable half servo throttle.

97 + also gets you the electronic shift 722.6 To make this work you will need the ABS computer and feed it with the proper road speed pulse. This can be done by using a electronic speedo fooler to get the ratio the trans computer is expecting.
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  #9  
Old 10-16-2018, 03:08 PM
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The way they get they greater displacement than you would expect given the stock stroke for the diesel crank is by offset grinding it when they modify it because the diesel has a larger journal for the rods.

I think this would be a fun project. Getting the work done will be expensive though and it will be hard to justify the cost for the added displacement if your goal is simply power, and not low end grunt, without a better flowing head. From experience with a stock cam stock head 3L M103 you can rev it well past the point where the head chokes and you stop making power. Porting the head would be a must and I would also be concerned with valvetrain stability. Another issue will be the trans. You will need to find a way to move the shift points assuming its auto. The 722.3 is a mechanical trans and I don't know how you would do that but it seems like people do modify those transmissions.

Because I want to fantasize about this the way I would do it is use a 3.2 M104 bottom end with a DOHC 3.0 24v "m103" head assuming the reason you really want to do this is keep the primitive fuel injection. The M104 has higher compression and slightly higher capacity and piston speed is not an issue at any reasonable RPM with the stroke on these engines. The 24v head flows way better than the 12V head could ever hope to as well.
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  #10  
Old 10-16-2018, 04:07 PM
ttownthomas
 
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Quote:
Originally Posted by Mighty190 View Post
use a 3.2 M104 bottom end with a DOHC 3.0 24v "m103" head assuming the reason you really want to do this is keep the primitive fuel injection. The M104 has higher compression and slightly higher capacity and piston speed is not an issue at any reasonable RPM with the stroke on these engines. The 24v head flows way better than the 12V head could ever hope to as well.
I'm confused about the DOHC 3.0 24v "m103" head part...Can you elaborate?
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  #11  
Old 10-16-2018, 08:14 PM
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Quote:
Originally Posted by ttownthomas View Post
I'm confused about the DOHC 3.0 24v "m103" head part...Can you elaborate?
This engine was found on 89 - 91 ish 300SL / 300CE / and an S class I think. It is , for the most part, a first gen M104 but the head won't interchange with the later M104 due to intake ports being different.

This engine isn't worth considering because CIS / K jet is $$$ to get working properly and does not like changes.
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  #12  
Old 10-16-2018, 08:23 PM
ttownthomas
 
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Ahh. And then the cis-e could be retained you think? I like this idea. Would I take the whole short block from the 104 and mate it to the 24v head? Or just the crank and Pistons?

Last edited by ttownthomas; 10-16-2018 at 08:38 PM.
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  #13  
Old 10-17-2018, 07:26 AM
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NNNnnOOoooo. Stay completely away from any version of CIS, you will spend $$$$ for no good reason.

Someone else on this site is going through the mess of mixing a late 3.2 block with a early 3.0 - 24 V head. There is absolutely no gain mixing early and late blocks / heads given a 3.2 24V M104 exists as a complete drop in.

I'm all for interesting combinations but no one is even going to notice such an arcane mix of parts.

Project goals need to be better defined before going any farther. ( RE What car , use of car, Budget )
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  #14  
Old 10-17-2018, 10:18 AM
ttownthomas
 
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OK...My original plan in my head:

1. I have a California clean 1990 300 SEL. It is not particularly option ladened and I think that is good for long term ownership costs. No SLS, no ASD, No power rear seats etc.

2. It is too slow. But I'm not looking for blistering. I just got rid of my 3rd porsche in a row but the family is getting taller and another porsche is not in the cards right now. Last one was a 930 but I dont need anywhere near that level of quick out of this car. The car weighs 3500 pounds give or take so Id like to get close to 14lbs per HP.

3. I want to rebuild a motor for performance because of the education that will come with it and because I like projects.

4. I figure somewhere between 225-250 horsepower can be extracted out of the current fuel system without reinventing the wheel and I assume that that can be done with an engine build and a full exhaust system. <-this is the primary focus of my question

5. It looks like there are alot of small bodied benzes with this motor that have decent aftermarket support in europe so I figured there were parts and specs available to do a build like this.

6. I really think that AMG already did the engineering work on the 3.0 and 3.2 versions of this 12v motor. So I figured that was a good place to start.

Goals:

225-250 naturally aspirated horsepower out of my current healthy 3.0 M103 without messing with stand-alone EFI. It already has CIS-E. Why ditch it if it still works.

I dont know how much it would cost to have a head ported, and flowed and valve-train lightened but if it was less than $2000 I would be shocked.

I figure it would be another $1200-$1800 for an engine back exhaust system

A cam will probably be $500

Not sure about the cost or availability of a 3.5 crank or the cost to modify it

Not sure about the cost or availability of lighter pistons and the connecting hardware.

I will be putting on H&R lowering springs and all new rubber in the suspension. but will retain the comfort billsteins for road manners.
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  #15  
Old 10-17-2018, 12:12 PM
ttownthomas
 
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Quote:
Originally Posted by 97 SL320 View Post
a 3.2 24V M104 exists as a complete drop in.
How involved is this swap?
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