Useful 3.2L M104 Specs and using Honda Connecting Rods - Page 9 - PeachParts Mercedes-Benz Forum

400Eric · #**121** 06-21-2012, 07:40 AM

I believe the 2.8 M104's rods are 149 mm too, not 148 mm.
Regards, Eric

whatever · #**122** 06-27-2012, 07:09 PM

I've got some info on OM603 92.4 mm crank in AMG 3.6 engine.

Pretty simple:

the OM603 3.5 L crank fits M104/M103 with minor machining:

the con-rods are simple 145 mm ones, but the piston is really short

The piston has a rough comp height of 27 mm (26.9 mm actual).
Here comes some shocking info on the rings:
1 mm - 1.2 mm - 2 mm
Which is really really really damn tight.

But actual "racing" pistons usually have same comp height with larger rings (oil ring intersects into the pin bore), like on these Nissan L28 pistons, which I have for the 3.1L stroker.

My 2 cents.

Modern Focus 1.6 Ti-VCT engine has a 25 mm compression height with some decent rings (I can take a pic, if interested). The only REAL problem is that con-rods are designed to have a small end to deal with side clearance. So finding off-shelf pistons is quiet a problem.
I heard some inserts can be made to control the gap between con-rod and pistons (when small end is dealing with side clearance)

400Eric · #**123** 06-28-2012, 02:29 AM

Great post with useful information! Thanks!

Are these parts in the photos from a C36 engine or are they from an older 3.6 AMG?
Regards, Eric

oldsinner111 · #**124** 06-28-2012, 05:04 AM

Pardon me: Does building a engine to 12:compression,do the same as turbo charging? Is it same power output?

400Eric · #**125** 06-28-2012, 09:28 AM

No. It would improve power by about 8% over your current 10 to 1 (assuming you get gas of sufficient octane) but a Turbo would add way more than 8% (assuming you get gas of sufficient octane).

You are thinking though, and that's good! Keep it up!

Now if only I could get you to start thinking about a lighter car!

Regards, Eric

oldsinner111 · #**126** 06-28-2012, 09:45 AM

Thank You Eric:I guess with enough compression you'd auto ignite the gasoline too

JayRash · #**127** 06-28-2012, 12:42 PM

pls post pics of the focus piston

MAG58 · #**128** 06-28-2012, 02:47 PM

Quote:

Originally Posted by JayRash

pls post pics of the focus piston

I doubt it would matter much. That focus has a 79mm bore. That's a few shy of 91.

JayRash · #**129** 06-28-2012, 03:18 PM

Just wanna see the piston

MrC36 · #**130** 06-28-2012, 09:44 PM

Wow now im lost, so m104 3.2 rods are the same as m104 C36 rods?

400Eric · #**131** 06-29-2012, 07:37 AM

I had been under the impression that the C36 used the 2.8's 149 mm rod so that the rod ratio wouldn't be such a rotten 1.57 to 1 but I guess there just isn't enough room in our little blocks for that.
Regards, Eric

MAG58 · #**132** 06-29-2012, 09:26 AM

Quote:

Originally Posted by 400Eric

I had been under the impression that the C36 used the 2.8's 149 mm rod so that the rod ratio wouldn't be such a rotten 1.57 to 1 but I guess there just isn't enough room in our little blocks for that.
Regards, Eric

You have 217.625mm to deal with, only so much you can do...
And if it makes you feel better, for the 91mm stroke, BMW puts 139mm rods in their S54.

whipplem104 · #**133** 06-29-2012, 07:47 PM

Mag58 is right. On the 3.6 motor there is not any room to change that much. The pin is already in the oil ring groove and honestly you are not going to spin the motor hard enough to make all that much difference. The 3.2l has a good ratio and is inherently cheaper to do anything to. Go high compression for n/a or go with boost or nos. The more I think about the more I look at the 3.6 as good for what it is and nothing more. Maybe a small shot and that is it. Otherwise the standard m104 either the 2.8 or the 3.2 is much better and parts are cheap and easy to get.

whatever · #**134** 06-29-2012, 11:44 PM

Quote:

Originally Posted by 400Eric

I had been under the impression that the C36 used the 2.8's 149 mm rod so that the rod ratio wouldn't be such a rotten 1.57 to 1 but I guess there just isn't enough room in our little blocks for that.
Regards, Eric

Yup, that's what I was thinking about too! But it's not possible much.
2.8 has 148 mm rods, don't they?

I think about modifying M111 2.3 OEM pistons with 145 mm rods.
Slightly mill the top (as I have M103 and I don't care about the 4V notches), mill the head a bit and use a thicker soft steel gasket (CAD design and laser cutting FTW). HKS (japanese tuner) used that trick and produced 2 mm head gasket for Nissan L28, when pistons were slightly sticking out. Too bad, M103/M104 aren't much funny to play with, because you have a water passage between the bores.

The 2.3 came with N/A and Kompressor type pistons. All of them have 30 mm comp. height. The 2.3K pistons are 2 types: with -1.10 mm dish and -2.30 mm dish, which is good for milling. Remember, when you stroke the engine, keep in mind that compression ratio would rapidly increase. That's why all diesels have big stroke, not bore.
The rings on the 2.3s are 1.5-1.75-3.

Head-gasket-wise, Elring company is pretty friendly when you need a custom gasket. Just to let you know, if you ever come across the need of something special.

To tell the truth, from my calculations, a good rebuild with good cams (or a cam for M103

) can do more power for the same money (doing a stroker), but it has nothing to do with increase in low speed torque, which pays back on the highway.

P.S. I'll upload the Focus pistons, once I get my camera back from the car.

400Eric · #**135** 06-30-2012, 03:47 AM

Again, I am petty confident that the 2.8 M104's rods are 149 mm, not 148 mm.

Are those parts in the photos from a C36 engine or are they from an older 3.6 AMG?
Regards, Eric