Some technical M120 questions.
 

Hello, I have some fairly technical questions about the M120 while I attempt to source one for a build. I have a line on a 97 S600 at the moment. I'll likely be developing a lot of parts during this build as the current aftermarket is either non-existent, or far too expensive.

1. Does anyone know the deck height of the block or the deck clearance of the pistons when installed? This would help tremendously with compression ratio calculations.

2. It appears the intake cams are reverse rotation being on the opposite side of the timing chain. Will an exhaust cam technically bolt in place of an intake cam? I don't need to be able to hook the chain up if so, I just need to know if it can physically go in place, with or without the cam gear, without any problems with oiling.

3. What is the length of the block, from front to back? I could also use measurements of the intake manifold of the intake runners closest to the flange, from the front of the furthest forward to the rear of the furthest back.

4. What is the valve angle on the heads?

6. Does anyone have physical measurements of the valves themselves? I think I've found valve diameter, but not length or stem diameter.

7. How strong are the crankshafts known to be? Can they handle a couple thousand more RPM than stock? Specifically the crankshaft, and none of the other rotating assembly. This would be the hardest part for me to find a suitable replacement for ($$$).

8. Are there any well-known issues I should be aware of in relation to oiling or cooling?

Would having a spare intake manifold help you? I just happen to have one on my trophy wall. The measurement top to bottom of the mounting flange is 595mm.

One side of the V12 is an M104 motor. Same valves, same head, it should have the same dimensions you are looking for info on. The big differences include the M104 block is cast iron and that the M120 carries a mirror image M104 block in tandem.

I would expect the stock crank to meet your needs. It's alloy block that should turn out to be your limiting factor.

-CTH

A spare intake manifold might help. I could get all of the measurements I need, get it scanned for a CAD drawing, and design a new intake manifold from that. I might have to cut it up to get inside shape/measurements of the runners though. What would your asking price be?

I'll try to get information from the M104 on valve/valve spring sizing and specs, but it seems possible that the M120 didn't use the same hardware, considering how many changes in valve sizes the M104 itself went through.

I'm hoping that an exhaust cam will bolt in place of an intake cam, so I can set the lobe separation angle and spin them both in the same direction. This will also make it much easier when dealing with having them reground, either through base circle reduction or welding and reprofiling. From there I can either work on new tensioners, or a conversion to timing belt. The water pump will be replaced to move it out of the way. New flanges will be cut and an electric remote mount pump will be used, this would help with redesigning chain guides or converting to belt.

The crank is my main concern. The only possibility of an upgrade would be billet.

I've seen that crank, it's impressive. I don't think you'll have a problem if you're only going for 2x HP from stock.

Share your finalized CAD diagrams with us when the smoke settles and the intake is yours for the price of shipping. It's heavy. I bet a 30HP gain would be gotten by 3D print of the manifold in a suitable plastic.

-CTH

The first step is sourcing an M120. Ebay has a few for sale for ~$4000. There are also 2 complete cars within 4 hours of me for less than the cost of an engine on ebay, but neither owner is very receptive to questions.

I've done enough searching to find off-the-shelf parts to replace a lot of the weak points of the M120 at a small fraction of the cost of buying actual M120 parts, so sourcing a high mileage engine isn't out of the question.

Gone are the days of 1500$ s600 and 600sel cars that owners just want to see go away. -cth

I think I saw a few in Bay Area Pick n Pulls back in the day. I once found a rust free 280SE 4.5 that had just showed up. Got the rear axle out during lunch time. I also saw a intact un crashed XJ12 once.

I'm hopefully picking up a car Monday for $2300. Fairly low miles, in good shape, with electric/ECU issues. I have a spare MS3Pro sitting around, I would just need to order another harness to get it wired and fired assuming that it is indeed an ECU problem.

Doing some digging, I just want to confirm that an M104 exhaust cam will fit physically (ignore the gear/sprocket) into an M104 passenger side head. The firing order should be correct, and the head is technically a standard M104 head on that side.

I want to buy a spare camshaft for measurements to look into having custom cams made. This camshaft could potentially be shipped off and the odds of it going back into the engine are very low, so I want to make sure I get a spare.

I now have the car in my possession and it is running. There are some electrical problems, but I plan on getting those out of the way before diving into the build.

Edit: Since I now own the car so my questioning has greatly shifted, and because this forum seems pretty dead, I'll probably end this thread here.
Maybe I'll document the build somewhere.

:2thumbsup

One thing you will want to consider is do you want the center sump M120 like from the W140' or the Forward type sump like from the R129 SL's. Center sump oil pans are cheep. SL forward sump pans are going for $700+. And to change over you need the upper and lower pan, the pump and the baffles. Might as well get a short block.

Or I can just convert to dry sump. Lots of OEM cars coming with dry sumps now so they're not too hard to find. I could fabricate a pan and pickup easily enough, especially if mid sump pans are cheap enough that I could find a reasonable spare.

I'm far more in favor of doing labor and fabrication than spending money. I've done my share of big power on the extreme cheap.

I've already ordered the harness to convert my S600 to use my spare MS3Pro so I can start tearing out enough emissions equipment to gain room for header fabrication. I'll measure clearance for various pan types while I'm down there.

Yes the center sump will be a lot cheaper and I do know one guy that modified his pump inlet to work with the forward sump. Pay attentions to the baffles, they are different, I'm not sure what the difference is.

There may be a guy in FL making dry sump conversions for the M120. At least he makes a lot of other stuff so worth checking him out.

https://www.gooichimotors.com/m120-v12-parts

I've looked into Goochi, but decided they're a bit unreasonable because of their love of titanium.

Yes I noticed they don't give a price for the dry sump system. My guess it if you have to ask it's too expensive. But I am interested in the remote oil filter plate and the water pump plates. Still expensive and I could make those but with design time for one unit probably would not be worth it. But I would love to know what a set of heads cost.

I'll probably skip dry sump due to costs. I'll baffle and trap door the wet sump pan and run an Accusump to cover situations where the oil pressure still has problems. This is considerably cheaper than a dry sump setup, and I should be able to do it all for less than $650.

For the water pump, its possible that I have some flanges cut out and run a remote electric pump, which I've had great success with in the past. The same company that makes the water pump I've done so well with also makes thin-mount brushless electric fans that are capable of some insane flow numbers for their size.

I already have a pump and fan sitting around for another project, I may borrow them for the time being.

Small update:

GM LS truck injectors with injector hats fit directly in place of the stock M120injectors, and are basically free. I had dozens of sets laying around that people were throwing away (LS swaps are huge in this area). They flow about 5% more than the stock injectors and are nearly infinitely replaceable. There are also some in the later years that have newer USCAR/EV6 connectors and flow more than twice what the stock MB injectors did, and are absurdly cheap.
Stock LS1/LS6 injectors will fit without injector hats. They're about 2mm longer than M120 injectors but fit just fine. LS3 injectors fit with injector hats.

Obviously these wouldn't be drop-in on the stock M120 ECUs, but for swaps they are perfect.

Who's making your fan. I had to resort to modifying one from a W211 and develop a PWM control for it. I couldn't find anything as thin as the 211 fan and at 19" and 600W, cooling is no longer an issue.

I started with a W203 fan but later found the W211 fan to work out much better. You can see my fan development starting at post 1060, here.

https://www.benzworld.org/threads/theres-a-new-one-coming.2876217/page-53

I use DeltaPAG for my fans/water pump. I first heard about them at PRI several years ago. They have their fans and water pumps on display there and was blown away by how well they perform, especially for their size. An 18" version flows over 4000 CFM at just 26 amps and the motor itself is dead silent.

Interesting fan. When I did mine, I couldn't find anything over 16". My biggest problem fan depth. The best I could find at the time was a flex-a-lite low boy with a 3-3/16" depth. It barely cleared, but it had 3000CFM and worked well on my car for 10 years until I installed AC. Not sure if 4000CFM would have done the job. The fan I used was from a 211 and was 19" and 600W. That's about 50 Amps. There is no published data but I would expect these fans to run over 5000CFM. There is also a 203 fan with the same size and power and a larger 850W fan used in some of the ML's. You can see Mr Duxthe1's thread here where the Arduino controller was developed. It also has my tail of fitting both the 203 and 211 fan's

http://www.peachparts.com/shopforum/mercedes-benz-performance-paddock/374351-124-electric-fan.html

I've ordered tubing and collectors to do a set of 6-1 headers in mild steel. Looks like I'll have about $3000 total invested once done, but that includes a fair amount of tooling as well. A second set would likely cost me about $1500. This is for 24 to 30 inches of equal length primary tubing (tubing length will ultimately be decided by fitment) in 1.75" diameter. If I can sell the first set for what I have invested, the tooling will ultimately be free, and I may even start building them out of stainless.

1.75" should be pretty large for each pipes. That's the same size the 2 down pipes on the M120. How does that compare to the exhaust port sizing. I did find fabricating the exhaust to me one of the most expensive parts of doing the job and I didn't even do headers yet.

Smaller than 1.75" isn't economical enough for me to consider, as I wouldn't use the tubing or the tooling for anything else. The only way I could justify a smaller 1.625" diameter is if I had buy-ins for manifolds from 3 people.

1.75" will actually fit nicely, if I up my goals a bit for power.

Are you bending tube yourself with a mandrel bender? Or are you working with mandrel bends. I cant see $3000 unless you are buying mandrel bending dies of multiple radius?

I buy pre-bent mandrel tubing. The additional costs are for clamps, fixtures, jigs, expanders, bandsaw fixtures, etc to be able to make a reproducible product. Once I make one, I can duplicate it without the car. It is a one time buy-in which typically pays for itself.

After doing some math, I am leaning towards the 1 5/8" tubing. It is right in that sweet spot of what I need currently, but it isn't without it's limits.

I've ordered 2 sets of exhaust header flanges, and 2 sets of merge collectors. These first sets will be mild steel, until I can get some flanges cut from stainless.

I will be pretty much working on the same thing using the same methods but without headers. In my case I need 1.75" all of the same radius except for 1 bend at the exhaust flange needs to be a little tighter. After that they merge into 2.5 which is all straight pipe. Then they merge into a single 3" all of a single radius. So at most I need 3 band saw cut jigs, which I hope ot just be able to fabricate,

Where did you get your M120 exhaust flanges from?

I found someone that had some left in stock and ordered 4 flanges. Look for M104 flanges instead of M120 flanges. The M104 flange fits directly on the other head.

I've solved my spark plug and plug wire problems. I've moved from a heat range 8 to a heat range 5 plug (they're also considerably cheaper). The plug wires I sourced from another car, and the boots are a direct fit, they even seal over the holes in the valve covers perfectly, snapping into place. The only issue I've found is that the terminals are about 4mm too short to clip onto the plug terminal, so I squeezed some lube in between the wire and boot and pulled the terminals down 4mm to allow them to clip into place. I also ordered 2 sets of LS coil boots. I'll cut the coil ends off of the wires and add the LS coil boots to them. All-in for custom wires that fit the valve covers better than the OEM COP boots and also fit my LS coils.. <$100 and about 2 hours worth of work.

Injectors are in as well. LS truck injectors with the aluminum hats to allow them to fit a factory LS1 intake ($16) and they dropped right in place.

Total invested so far:
-Plug wires ($89)
-Injectors ($0): Pulled from trashed intake manifolds.
-Injector hats ($32)
-New injector O-rings ($14)
-Ignition Coils ($0): Leftovers from buying/selling LS engines.
-Spark Plugs ($44)
-Header Flanges ($110)
-75mm Cable Throttle Bodies x2 ($70)
-MS3Pro wiring harness ($300)
Total: $659

With the sensors I need, plus a few misc connectors, I figure I'm probably $300 shy of having it running and tuned on the MS3Pro, putting me in at just under $1000.

With power steering/AC delete, electric fan, greatly improved ignition, aggressive fuel/timing and conversion to run on E85.. I'm hoping the original 389 HP comes out closer to 440 (I don't see this being any problem). The MS3Pro will be used to control the VVT for optimal power and torque.

Exhaust headers will be the very next step. It looks like 1.625" primaries in 16 gauge mild steel, with 6-1 collectors that merge into 3" (2.5" with a 3" expansion may be used). Primary tube length between 24 and 28" depending on problems with fitment on the driver's side. Possibly a custom X-pipe afterwards depending on the exhaust tone when finished. This should put me around 465-475 horsepower which is where you typically end up with 6.0 LS engines after just cam/headers.

Maybe I'll be able to break 500 with an intake manifold. Unlikely as the factory piece isn't very restrictive, but the runner length and plenum design leaves a lot to be desired.

I'm just wondering what kind of car you are putting 6 into 1 collectors and 24"+. I don't see me having a hope in hell on my 107.

I also think you will find that the published 389HP is very conservative. I got 355 on a chassis dyno and didn't even get it into 1:1 4th gear on the dyno, so I was still going through a planetary reduction.

I'm going to attempt to make a set for the W140 that the engine currently resides in, before pulling it out. The steering box is the biggest obstacle. Once the set is finished, I'll probably pull the engine and scrap the car. This will allow me to get a decent base tune as well and do some exhaust note tuning.

The headers will be listed for sale once the engine is out of the car.

Definitely post some pictures.

just to confirm about the injectors. im having trouble sourcing replacements for the m120. i can use ls ones? but cant drop in on stock ecu ?

I've sent you an email. It doesn't answer you question, but it does suggest a better place to ask it, in case it doesn't get seen here. -CTH

I can't say for sure. Flow rates are somewhat close. I don't know the difference in resistance values for them or the dead time.

I assume it would indeed run on the cheap LS truck injectors on the stock ECUs, but how close to OEM it would run and how much the difference in resistances would affect the stock ECU are important questions to have answered.

That email also offered you the 8 M120 injectors I have here, if that helps you.

-CTH

I'm still here, just busy. I insulated and installed a mini-split in the garage for climate control, and put in a new lift.

I'm close to starting on the headers, I have one other car to finish up first.

I'm about to start on the headers. I'll try to post some pics but mobile photo uploads are disabled on the forum.

Here, an image of the flanges/collectors at least.

Nice work.

I'm glad I found this thread- following with interest.

I am doing an M120 swap into an old Toyota Supra.

I'll be running Maxxecu- don't think I will be able to keep the vvt. I'm interested where you end up with cams. I would love to build a top end for 8k+ redline if that's doable.

I'm going itbs for space reasons and to be able to run a single e-throttle instead of 2.

Not 100% sure if I can make the front sump work or if dry sump will be required. So far bottom of pan hits the sway bar.

If you are posting your progress somewhere else as well I would love to know.

I got to wondering if there was a Facebook group for folks modifying the M120 or swapping it into other vehicles- I couldn’t find any, so I just created one. I’m the only member so far but don’t be shy if you want to join

https://www.facebook.com/share/g/iK4WSBAs19DhnLsb/?mibextid=K35XfP

I have 3 other cars I'm trying to get finished before it gets too cold, then I'll be starting up on this one again. The front of the car is torn down enough for me to get started on the headers, but I haven't made a move on it just yet.

The VVT is just on/off. If you can do custom tables in Maxx then it should be easy to control it.

ITBs are great, but with the downside of complexity.

Sway bars can be changed to a different style or relocated.

I have some options for cams right now, from easiest to most difficult:
-Pay Gooichi a small fortune for cams ($4k/set to start IIRC).
-Find a cam grinder in the US that will regrind them (I've found several potential candidates, $1200-1800).
-Ship them to the existing regrinders in Germany to have them done and shipped back (dbilas or Renntech, $1400-200).
-Reconfigure the timing chain to run on top of the intake cams instead of underneath, allowing use of M104 cams which are more readily available.

I've decided not to build headers for the W140, as it is just too much of a pain for such little benefit. The M120 will be coming out of the car soon, and onto the stand.

I just joined

I just joined as well.