M104 Cylinder Head differences...
 

Now that I've pulled apart a 2.8, 3.0, and 3.2 M104 I've got a few questions to ask about these heads...

The biggest one is, which cylinder head design flows best? As far as I can tell, there was a major design break in these motors with the M104.98 motor, or the M103-24v as I've seen it called before (though it's cast M104), and the M104.94/.99 series of heads. The exhaust is the same on both head designs, the manifolds have the same flange etc., but that's about where the similarity ends.

Cue pics...
This is the late model head, that came out of a late W124 chassis car. The water port is on the front of the head and there is a slider on the intake side of the chain drive, not a roller.
http://i674.photobucket.com/albums/v...a/DSCN0108.jpg
Pay no attention to the datsun head below it, that was for something else.

Now this is the M104.980 head that I got when I pulled the motor out of a 1990 300CE-24. If you notice, the way the intake manifold mounts is much different as is the overall intake port design.
http://i674.photobucket.com/albums/v...a/DSCN4121.jpg
Another interesting thing to note is that the valves are less visable on this engine as the angle cut on the intake mounting flange is actually opposite the angle cut on the later M104 head. That is to say, that this head was designed so that when the engine is mounted in the car at its 15 degree lean over, the intake mating surface is exactly vertical while the later model head has a pronounced angle to it, making the efi intake mount at a much more radical upward angle (if that makes sense.)

Also, on this early model head, it has a tensioner sprocket located right below the intake cam, and the water outlet is directly on the side of the block, in the same location as the M103 water outlet (which I'm pretty sure is why it's there).
http://i674.photobucket.com/albums/v...a/DSCN4123.jpg

Vs...again, don't pay attention to the datsun block it's sitting on...
http://i674.photobucket.com/albums/v...a/DSCN0111.jpg

So the question is, which head flows better? Before anyone gets carried away with CIS vs EFI or displacement, lets talk about head design. The car it's going in is very light unless I can find a 190 2.6 with a blown motor/no drive train so I can stuff it in that and even with the most radical cams possible (which will at some point happen, just not at the beginning) the motor will have enough torque for anything I'd like to do. Also either way the engine will be running MS3 so again, induction system will be pointless. At this moment let's just discuss head and engine design.

Neat stuff! I wish there was more of this kind of stuff around here!

My money is on the later head even though the earlier engine made more horsepower with less displacement which I would guess is because the older version had wilder cam specs ( just my theory but I bet I'm right).

At this point you may in fact know more on this topic than most anyone else here does.

Please keep us posted of your findings!
Regards, Eric

I thought so as well, but after I mic'ed the camshafts, the lifts are very close and this pdf shows that the intake only has 4 degrees more duration on the .98 and the exhaust cam is the same, though indexed 1 degree off of the .98 motors.
http://www.ps2cho.net/downloads/MB%20CD/W124/w124CD1/Program/Engine/104/05-2210.pdf

Also, though my german is pretty poor at best (if anyone cares to call the German national library and find out how to get it in english, the publisher only has back copies to 2001, this is 1998), the article below discusses how the M104.98 was designed with emphasis on performance while .94/.99 were designed more with global sustainability/ability to pass smog in mind.
http://www.pvv.org/~syljua/merc/M104Motor.pdf

I feel that with the Efi as opposed to the CIS of the earlier motors, that the later model engine should at least even with the 4 degrees less duration, you'd see more horsepower out of 3.2L...

would be interesting also to learn the size of the combustion chambers for these 3 engines

somewhat searching as to any size differences in chambers between the m103 heads from the 3.0 and the 2.6

I would say that pretty much the later head will outflow the older one. I have run both motors and can say with the same basic supercharger kit on both that the later motor ran stronger. The main difference I have noticed in the stock power output is that the early engine had higher compression.
The easiest thing to do though is go have both of them flow tested on a bench.
I also was comparing the c36 head the other day to standard 3.2l head and the only noticeable difference in that head was the exhaust was ported out to gasket match. The bowls on both the intake and exhaust were cleaned up but that was it and the head flows significantly better than the 3.2l.
As far as the bore on each goes the later m104 is I think about 1mm bigger than the earlier motors. The stroke is the same. In fact I have stroked a 2.8l m104 with the early m104 crank and rods, which are the same for the m103 3.0l also.

Were you running CIS on the .98 or were you running EFI on both?
After seeing both models of blocks, I personally think the early block is a little stronger with much larger webbing on the inside of the block. Either way, the .98 is the same bore/stroke (88.5x80.4) as the M103 while the later models use the 89.9mm bore. in us, that means 60 thou more cylinder wall, good for boost!

Another think I'm seeing on the earlier head there is much more room on the intake to port, and the ports are much rougher, while the later model head has a much smoother intake port. The later port also has very little room to actually cut into for porting. Hmm, I have both heads, I guess the next step is the flow bench.

Anyone have any good suggestions for a place to get the heads flow tested in the Midwest? I'm in the middle of indiana and there's pretty slim pickin's.


Another note as well, Colt Cams of Canada said that they can do M104 regrinds for 4-500 for the pair with whatever grind you like (provided it can be put on the core) including beveling and parkerizing. As I talked to the owner, he said he had literally hundreds of thousands of hydraulic profiles on hand and since he has not done an M104 before (he's done M110's and M103's) that he would be the one analyzing the cams and cutting them.

Food for thought.

The short side radius of the early head is just awful. My money stays on the later head.

We have simply got to get that engineering paper translated into English!

All M104s have 10.0 to one compression. The only exception is the C36 version which is 10.5 to one.

The C36 was taken out another 60 thou over the later M104 so I would think the later M104 is still beefy enough for boost.

Somewhere around here is a thread where a guy tried to put a 3.5 diesel crank in an early block only to find that the rods hit the bottom of the bores. He found that everything fit the later block easily. (This diesel crank, along with the overbore, is of course how the C36 was created.) The 3.6 held up just fine with that later block. These are also things to consider when weighing the early vs. late blocks.
Regards, Eric

Hmm. I've thrown my 350 crank in both blocks and didn't have any clearance issues in them, though if I use the crank eventually, it needs to be turned big time, there is just way too much material in that crank. It probably weighs half again as much as my 300 crank! Also, with 280 rods (149mm) the piston sticks out some .385 proud out the top of the block...

The later block, but it fits both
http://i674.photobucket.com/albums/v...a/DSCN0167.jpg
!
http://i674.photobucket.com/albums/v...a/DSCN0169.jpg

Running the 350 crank would still give me 3.4L in the .980 block.

Whipple, could you post some pics of your C36 head? I've never actually seen one before. I've also heard that these heads have been altered a bit in the CC to get it large enough to get the CR down to 10.5...?

on the 36AMG engine i think the piston pin sits 1mm higher in the piston.

According to carfolio.com,

1993 320CE:
Bore × stroke 89.90 mm × 84.00 mm

1989 300CE-24:
Bore × stroke 88.50 mm × 80.25 mm

1993 280E:
Bore × stroke 89.90 mm × 73.50 mm

Correct. and also

M104 3.6L (The AMG variant)

Bore x stroke: 91mm x 92.40mm

Also.
Rod Length:

M104.94x = 149mm
M104.98/.99= 145mm
C36/Barabus/?=??mm

But... The bottom end is another topic entirely! Lets keep it to head design! (after semi-hijacking my own thread)

i know im off topic but bare with me

the M104 2.8 seems really good for a high rev conversion, fit solid lifters and stronger vavlve springs with stand alone ecu and a good cam and this engine can rev to over 8k safe since piston speed should be lower due to the crank it has, thus piston rings wont flutter at high revs.

My money's on the early design. Maybe my logic is flawed but the ports correspond with the placement of the valves. Whereas the circular ones don't. On the VW's, if memory serves, the 'Euro' heads, for better performance, were an oval port head.

Precisely what I plan to do!;)

If you're looking at mean piston speed, the 2.8 can go to 10.5k iirc before piston speed becomes an issue, the 3.0 can go well above 9. (assuming 25m/s max piston speeed). If you really want a screaming engine, build a long rod 3.0 with the smaller (lighter) pistons so you can have the 3.0 bore, long r/s ratio (well above 1.75) which should produce less piston acceleration at the extremes leading to a VERY smooth high strung engine.