M120 Performance Build.
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Newbie
Joined: Jul 2024
Posts: 9
Likes: 1
97 S600
M120 Performance Build.
Hello.
I have recently purchased a non-running 97 S600 as a project car. It appears one bank isn't running and the alternator is bad. The car itself is in fairly rough shape. Fortunately, none of this matters as the primary focus was the engine. What happens with the car itself is still debatable, but for now it is staying put.
There are very sparce details online about these engines sadly. I'm coming from American V8s where everything has been measured, dissected, redesigned, lab tested, etc with all of the knowledge readily available everywhere you look, I've decided to switch to something that is more of a challenge.
The goals:
-Forged rods and pistons, aiming for reduced weight and increased compression ratio.
-Ported heads, larger valves, stronger valve springs.
-Custom exhaust manifolds. 6-into-1 collectors. Stainless, aiming to have these done for less than a quarter of the current price of aftermarket manifolds.
-Custom intake manifold. There is some debate here, but I have identified various options.
-Custom made camshafts. This is the trickiest bit by far.
-Improved oiling system. Dry-sump is the goal, but not the only option.
-Conversion to modern EFI, ignition coils, and ethanol fuel.
The first task is to get the car up and running.
Afterwards, I will likely go directly to an aftermarket EFI setup. I have a ton of questions, and I'll post most of my progress here.
I have recently purchased a non-running 97 S600 as a project car. It appears one bank isn't running and the alternator is bad. The car itself is in fairly rough shape. Fortunately, none of this matters as the primary focus was the engine. What happens with the car itself is still debatable, but for now it is staying put.
There are very sparce details online about these engines sadly. I'm coming from American V8s where everything has been measured, dissected, redesigned, lab tested, etc with all of the knowledge readily available everywhere you look, I've decided to switch to something that is more of a challenge.
The goals:
-Forged rods and pistons, aiming for reduced weight and increased compression ratio.
-Ported heads, larger valves, stronger valve springs.
-Custom exhaust manifolds. 6-into-1 collectors. Stainless, aiming to have these done for less than a quarter of the current price of aftermarket manifolds.
-Custom intake manifold. There is some debate here, but I have identified various options.
-Custom made camshafts. This is the trickiest bit by far.
-Improved oiling system. Dry-sump is the goal, but not the only option.
-Conversion to modern EFI, ignition coils, and ethanol fuel.
The first task is to get the car up and running.
Afterwards, I will likely go directly to an aftermarket EFI setup. I have a ton of questions, and I'll post most of my progress here.
Thread Starter
Newbie
Joined: Jul 2024
Posts: 9
Likes: 1
97 S600
Update: The non-running S600 is now running.
The alternator doesn't work and it is running on one bank.
Step 1 is get the car as functional as possible without spending any money, attempting to fix the problems with the alternator and passenger side bank (assuming it is a wiring/electrical problem).
Step 2 is to replace all of the engine electronics with my spare MS3Pro and get it running and tuned again.
Step 3 is to remove all emissions related hardware or anything else not being used by the MS3Pro to "simplify" the upgrade process.
The alternator doesn't work and it is running on one bank.
Step 1 is get the car as functional as possible without spending any money, attempting to fix the problems with the alternator and passenger side bank (assuming it is a wiring/electrical problem).
Step 2 is to replace all of the engine electronics with my spare MS3Pro and get it running and tuned again.
Step 3 is to remove all emissions related hardware or anything else not being used by the MS3Pro to "simplify" the upgrade process.
MBWorld Fanatic!
Joined: Feb 2012
Posts: 2,611
Likes: 1,209
From: Phoenix
222 S-65
OP AMG did a stroked crankshaft for seven liters of displacement.
Renn-Tech built them to make 600hp.
Nice four valve heads don’t have any problem getting air in and out.
The HUGE intake manifold with very long runners has always seemed overkill to me.
Well designed headers will certainly help.
Your 1997 should have individual coils. One bank is not running... start with looking for a blown fuse. Then why it blew. Wiring harnesses were famous for having the insulation turn to dust inside the cover anywhere the harness flexes.
Have fun with the project.
Renn-Tech built them to make 600hp.
Nice four valve heads don’t have any problem getting air in and out.
The HUGE intake manifold with very long runners has always seemed overkill to me.
Well designed headers will certainly help.
Your 1997 should have individual coils. One bank is not running... start with looking for a blown fuse. Then why it blew. Wiring harnesses were famous for having the insulation turn to dust inside the cover anywhere the harness flexes.
Have fun with the project.
Thread Starter
Newbie
Joined: Jul 2024
Posts: 9
Likes: 1
97 S600
The one bank not running is from a big nest of stuff blocking the MAF on one side.
600 HP is the goal. I have an engine dyno available so I will likely be testing it to confirm. There's a chance I install larger, lighter valves and maybe do some mild head porting. I already have a line on rods and pistons should I decide a noticeable increase in compression is needed.
I wouldn't say the intake is "overkill". The runner length is very much aimed towards mid-range power. I'll be replacing the intake manifold with a custom one.
The individual coils are getting replaced with some stock 5.3 LS truck coils, as are the injectors.
600 HP is the goal. I have an engine dyno available so I will likely be testing it to confirm. There's a chance I install larger, lighter valves and maybe do some mild head porting. I already have a line on rods and pistons should I decide a noticeable increase in compression is needed.
I wouldn't say the intake is "overkill". The runner length is very much aimed towards mid-range power. I'll be replacing the intake manifold with a custom one.
The individual coils are getting replaced with some stock 5.3 LS truck coils, as are the injectors.
Thread Starter
Newbie
Joined: Jul 2024
Posts: 9
Likes: 1
97 S600
The one bank not running is from a big nest of stuff blocking the MAF on one side.
600 HP is the goal. I have an engine dyno available so I will likely be testing it to confirm. There's a chance I install larger, lighter valves and maybe do some mild head porting. I already have a line on rods and pistons should I decide a noticeable increase in compression is needed.
I wouldn't say the intake is "overkill". The runner length is very much aimed towards mid-range power. I'll be replacing the intake manifold with a custom one.
The individual coils are getting replaced with some stock 5.3 LS truck coils, as are the injectors. This will make it significantly easier and cheaper to replace them in the future should a problem arise. They're also far better suited to what I'm trying to do.
600 HP is the goal. I have an engine dyno available so I will likely be testing it to confirm. There's a chance I install larger, lighter valves and maybe do some mild head porting. I already have a line on rods and pistons should I decide a noticeable increase in compression is needed.
I wouldn't say the intake is "overkill". The runner length is very much aimed towards mid-range power. I'll be replacing the intake manifold with a custom one.
The individual coils are getting replaced with some stock 5.3 LS truck coils, as are the injectors. This will make it significantly easier and cheaper to replace them in the future should a problem arise. They're also far better suited to what I'm trying to do.
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Thread Starter
Newbie
Joined: Jul 2024
Posts: 9
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97 S600
I'm starting with injector replacement.
Stock 4.8/5.3 GM truck injectors are the go-to. I've used these in everything from 4 cylinder engines to 800 HP turbo LS engines, and they're basically free as there are millions of these engines in the US and people who buy them for swaps and builds throw away the factory intakes and injectors.
Flow rate of the OEM MB injectors is listed as 208cc @ 3 bar.
Flow rate of the OEM truck injectors is listed as 220cc @ 3 bar.
Measuring them, they're a fair bit shorter than the OEM M120 injectors. The O-ring diameters are the same.
Injector lengths O-ring to O-ring:
M120: 2.455
LS Truck: 1.866
LS1: 2.550
Stock LS1 injectors are close enough that some thin washers under the fuel rail brackets will offset the difference in length, if needed. Adapters to use truck injectors in an LS1 intake/rail setup are $2.50/each, so for $30 I can adapt the truck injectors to the MB rail and intake, and have injectors that are free to replace. I will increase the fuel pressure to 58 PSI, which should give me plenty of room for power.
Upgrade options would be truck injectors from the later trucks, with cc/min flow rates averaging 440 cc/min (I already have 8 of these, I just need to source 4 more on the cheap) and I'll start with these instead.
Stock 4.8/5.3 GM truck injectors are the go-to. I've used these in everything from 4 cylinder engines to 800 HP turbo LS engines, and they're basically free as there are millions of these engines in the US and people who buy them for swaps and builds throw away the factory intakes and injectors.
Flow rate of the OEM MB injectors is listed as 208cc @ 3 bar.
Flow rate of the OEM truck injectors is listed as 220cc @ 3 bar.
Measuring them, they're a fair bit shorter than the OEM M120 injectors. The O-ring diameters are the same.
Injector lengths O-ring to O-ring:
M120: 2.455
LS Truck: 1.866
LS1: 2.550
Stock LS1 injectors are close enough that some thin washers under the fuel rail brackets will offset the difference in length, if needed. Adapters to use truck injectors in an LS1 intake/rail setup are $2.50/each, so for $30 I can adapt the truck injectors to the MB rail and intake, and have injectors that are free to replace. I will increase the fuel pressure to 58 PSI, which should give me plenty of room for power.
Upgrade options would be truck injectors from the later trucks, with cc/min flow rates averaging 440 cc/min (I already have 8 of these, I just need to source 4 more on the cheap) and I'll start with these instead.
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Thread Starter
Newbie
Joined: Jul 2024
Posts: 9
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97 S600
For the sake of curiosity, I'm considering building a set of equal length 6-1 headers for the M120 to fit the W140 since I'm using the car as a test-bed for the M120 until the time comes to pull the engine. I would only do this under the assumption I could get my money back out of them afterwards. Would it be unreasonable to think that I could get back out the $3000-3200 I would have fully invested in the exhaust, headers and X-pipe (possibly with mufflers)?
MBWorld Fanatic!
Joined: Feb 2012
Posts: 2,611
Likes: 1,209
From: Phoenix
222 S-65
For the sake of curiosity, I'm considering building a set of equal length 6-1 headers for the M120 to fit the W140 since I'm using the car as a test-bed for the M120 until the time comes to pull the engine. I would only do this under the assumption I could get my money back out of them afterwards. Would it be unreasonable to think that I could get back out the $3000-3200 I would have fully invested in the exhaust, headers and X-pipe (possibly with mufflers)?
Pretty small audience for a tarted up 120.
I’d sure love to hear it’s bent-12 song once complete.
Japanese guy did some lovely headers for an 120 powered S600 years ago.
Others have cooked up cam profiles to move the power band further up.
Thread Starter
Newbie
Joined: Jul 2024
Posts: 9
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97 S600
Can anyone confirm this?
I found a link showing the center-to-center length for M120 rods is 153.8mm
I've measured the rod a dozen times and come up with 154.8mm every time.
https://www.athousakis.gr/en/mpiela/...-mercedes.html
I found a link showing the center-to-center length for M120 rods is 153.8mm
I've measured the rod a dozen times and come up with 154.8mm every time.
https://www.athousakis.gr/en/mpiela/...-mercedes.html
MBWorld Fanatic!
Joined: Feb 2012
Posts: 2,611
Likes: 1,209
From: Phoenix
222 S-65
OP shove that pin as far up as you can and make up rods longer than stock. More time with the piston at TDC and BDC does good things.
