Why Not? Mercedes-Benz M104 stroker for my 240Z

[ravera]

I've already blasphemed most of the forums about this, so why not see what 'chall think. I recently acquired the "diesel" crank to build my 3.5L (90mm/92mm) Mercedes-Benz M104 Stroker motor (plus turbo maybe?) Anywho...

Pixorz.The little beastie as it sits, with it's Mild carbed L28:

And the beginnings of a monster...She's still going to be in pieces for a while until I finally figure out which way to go with it, and more importantly which transmission to wedge behind it...Block:

The Stroker Forged OM603 350SDL crank (top this, LD28...)

The Head is actually wrapped up, but when I had it out for my DOHC project (yes, this head fits on an L28. No mb/prince conspiracy now kids) I snapped some pics, and if you're thinking that intake looks like it came off a superbike, yes, it pretty much looks exactly like that:Compared with the L28 head (again, from my DOHC project):Exhaust side on L28 block, nice and meaty...Valve train side... And finally the combustion chambers... Yes, the valves are already larger than an RB26 head, with 1mm over what the stock RB intake is and 2mm over on the stock RB exhaust.

Lots of technical posts, most people haven't actually seen one of these motors. And before we get on a twin cam L series power trip, this motor is about 30lbs lighter than the L, fully counterweighted forged crank, oil squirters, the works and I got all the bits for about the price (maybe a little less) of a going L28ET.

Though the DOHC project should make a return after this beast is finished.

[evildky]

very clean 240, and very interesting swap

so are you strokign the diesel merc motor and runnign diesel? that head isn't from a diesel is it? the combusting chambers ..... it has combustion chambers

it's interesting that the head bolts up but do the oil and coolant passages line up? and of course thent here is the matter of running a chain fomr the crank pulley 2 cams on that head and your pic cut the end off but I'm guessing it's radically different, fwiw the rb ehad will blt to the L6 but the oil and coolant passages don't match, nissan has preserved their basic architecture for 40 year or so

does merc have a manual trans to bolt to that block? it's a lot easier to adapt your trans to the chassis than to adapt the datsun trans to the merc engine

as for the engine choice, ultimately if you are more comfortable with a merc motor go for it, I liek the L28et, I like fuel injectin and turbo's and thats what I' most comfortable with, some people prefer the 4 barrel holley because thats what they are comfortable with,some people prefer the su's me I'm not a fan of a vacume modulate fuel leak

[hbpignosePA]

neato

so the head is from a turbo benz too?

sorry it doesnt specifically say im just putting two and two together

[ravera]

The entire engine comes from an M104 Gas burner. The only diesel part is the OM603 crankshaft which gives me my 92mm stroke. The heads I have are from the .98 and .99 motors or the 3.0 and 3.2L displacements.

Yeah the head bolts line up and the rest of the stuff would be pretty simple, but that's another story.

I'm not a big fan of RB motors since there's a drive in me to never go smaller in displacement, so a Liter over the standard 25/26 would be in my game. And I never really cared for JZ engines since some how they managed to make them absurdly heavy.

This motor is going to be 3.5L, 30lbs lighter than an L28, has a gorgeous twin cam head, and a stock 10:1 3.0L motor made 400whp and 500wtq (yep, still more torq than horespower, ran out of turbo) on an unopened block and basically untouched fueling system (just added an extra injector controller) on 91 octane. So these motors have potential.

...Just have to figure out how much.

And two trannies fit, the 5 speed Getrag 260 out of a 2.3-16 or the 6 speed that came behind the M111 engines, though some of the auto's have removable bellhousings so making an adaptor to my choice of 5/6 speed shouldn't be difficult. The clutch is a direct bolt up from a 90-93 190E 2.6 as well.

[evildky]

I'm confused, you said you liked lower displacement but you are replacing the 2.8 with a 3.5, one that you are strokignt o achieve said displacement! and the msot popular RB's are the RB25 and RB26 which are 2.5 and 2.6 liters respetively so they are less displacement that the L28, the rb26 has the same bore, as the L28 and the stroke of the L24, whereas the L26 hs the stroke of the L28 witht he bore fo the L24

as for your trans options, adapting a manual trans to an auto bellhousing isn't all cookies and cream unless the merc trannies share a configuration, otherwise you are still left trying to get everythign centerd and runout within acceptable tollerances as well as fitting a starter to fet the flywheel and clutch mechanlcals to fit inside the bellhousing, if the getrag is a direct bolt in thats exactly what i'd do, they should have upgradable internal components if strength si an issue

[ravera]

I'm not a big fan of RB motors since there's a drive in me to never go smaller in displacement,

The starter bolts to the block. The starter actually makes zero contact with the transmission what so ever.

And I understand the concepts of having to re-zero the crankshaft and input shaft to one another. I'm really not worried about that either, just a lil' cad work and some CNC time and it's pretty easy. Well not "easy" but there have been more difficult things.

I like the getrag trans, they're tough as nails, but they're pricey, rare, and more importantly, a close ratio dog box with only a 1:1 top gear. None of those aspects lend themsleves well to turbo motors with big powerbands.

[kelloggman]

he said and i quote

I'm not a big fan of RB motors since there's a drive in me to never go smaller in displacement

[evildky]

doah, missed the "never" yeah I'm a fan of increased displacemetn as well

[hbpignosePA]

but is that not an l28 block?

sure looks liek it

[ravera]

*palms face*

Lol the pictures of the block on the engine stand (bare) is the M104 block.

The block the head is bolted on is the L28. Those pictures were from my DOHC project.

Now I have the M104 block, and more importantly the big crank, so the DOHC project has been put on hold.

[S130Z]

E-mazing!!!

I want to do a build like this! Will any other DOHC heads fit on the L28?? I know that one OS giken will but is near impossible acquiring.

[ravera]

I'm just gonna throw it out there... I'm NOT building a dohc L28+ right now.

I'm building a 3.5L M104 stroker.

The Head pics are just from when I was working on my DOHC project. That got put aside. 700CC's, fully counterweighted forged crank, oil squirters, lots of fun things the aging L28 doesn't have... So yea.

[evildky]

the L28 has oil squirters, and who needs a forged crank when you ahve 7 main bearings and the natural harmonic of an inline 6

[ravera]

In the root of the rods, which only serves to coat the walls of the cylinder half the time.

And considering the L series usually doesn't see 8+k for very long since it hits a natural harmonic barrier that it gets very unbalanced (the whole car vibrates with it) and then has a problem breaking the flange off the crankshaft at the #6 cylinder at that RPM Range, I'll take 12 counterweights over 8.

If an inline six was completely balanced without the need for 12 counterweights, why would BMW, Mercedes, Toyota, and even the Chev Vortec 4200 I6 not have 8 like the L?

Remember, putting the counterweights on the other side of the main bearings causes the torsional load that the opposing forces have to transmit through the bearings making them want to twist.

[evildky]

I didn't say the L6 was ballanced I said it had a natural harmonic of an inline 6, as opposed to an inline 4 or v8, the forces encountered internally on those engines are far less efficient than that of an inline 6, and of course your merc motor has the same inline 6 harmonic

not many engines see 8k rpm and there are ballanced race L6's that do, the FP 240's break cranks once in a while as they aren't allowed to ballance the bottom end and still run them at 8k rpm, and fwiw I used to run my n/a L24 at 8k, and it was smooth as glass, there is no power to be had up there with the stock carbs, head, and cam but it did it on a fairly regular basis, the shorter stroke is more stable as is the decreased rod angle and rod speed, which is why I ultimately decided against the stroker

my point was that crank failure on the L6 isn't common, it only tends to happen to race only cars that run sustained high rm's without the benefit of a ballanced rotating assembly

I have nothing against the merc build, I thik it's cool as hell, I just feel that a forged crank in a car taht has 7 mains is overkill, the crank you chose happens to be forged, but a non forged crank would not be a deal breaker

[ravera]

I can agree with that. Mercedes, like Nissan in the recent, have gone to fully forged cranks in all of their vehicles.

And due to the long stroke, I plan on using piston speed as more of a redline than actual rotating speed, as with the head design and the crank design, the pistons will fail from overspeed and the rods will stretch long before valve float with aftermarket springs really becomes and issue.Because of this, the max speed I would safely want to run an M104 w/ the stroker crank is 8600rpm, which gives a mean piston speed of 25m/s, which is about as fast as I feel it's safe to spin motors. F1 goes at about this speed, some honda motors can push past it, but engine life is drastically reduced. Actually It will probably see a redline of about 8k with a spark cut at about 8300.

If a stock 2.8 crank was used however the motor could safely spin 11k, but that's a little much for street use.

[Ptotherice]

I love this build so far man. How much and how hard are those motors to find? (If you don't mind me asking.) I'm always looking for an unorthodox swap to read into and possibly do. If this isn't too budget braking I might consider it. If you don't mind also giving some more information on the motor and all that good detail-y stuff (Feel free to email me at [email protected]).

[bigred240sx]

i like this swap and wanna see it done. dude last week yall would have lost me with all this crank and piston talk. i never knew much about it. but this first week at uti has been all about that. i love knowing whats beeing said.

[NSR_s30]

Very cool. Both the projects.

[ravera]

Go Go Gadget Gmail.

But anyways thanks for your interest fella's. I'm kinda torn between which way to go with this, but either way I think that I've figured out a way to use commonly available aftermarket parts to get the bottom end solved so we can dump it in the ol' gal this winter.

[ravera]

Quick update. Got to go home to play with the motor today, found a 280CE rod and piston out of a motor that threw one so I stuffed her in the block to see what she'd do.

This is the results:Crank in block...

The piston sitting .385 proudly out of the top of the block at TDC O.o:

...I'm scared.

Anywho, for those of you who wanted to know what the side of the block looks like here you go, it's nothing like the L series, tons of exterior ribbing and bracing with little extra material where it isn't needed:

[Ptotherice]

So... uhhh... where are the updates my man!?