M104 Cylinder Head differences... - Page 14 - PeachParts Mercedes-Benz Forum

kynsi · #1 05-29-2010, 12:36 PM

Quote:

Originally Posted by 400Eric

I'm not forgetting that the 2.3 and 2.5 M102s have a bigger, heavier piston but it wouldn't be an issue if people didn't wind the pee out of them.

I agree with everything you said in your post except for three things:
1) It's RPM not RPMs. You are counting the revolutions per minute not minutes.
2) It's engine not motor.

3)There are some exceptions as to what makes rods fail. Here are the rods from a mid 12 second turbo Volvo:

We are still trying to figure out why all 4 of the rods from this engine are bent and yet the stock, cast pistons are fine. Whatever was strong enough to hurt the rods should have hurt the pistons too. Honestly, I'd love to have a bright, sharp, insightful kid like you weigh in on the topic over there on the Volvo site: http://forums.turbobricks.com/showthread.php?t=204800&page=2

So the 2.5 16v also has 149mm rods? It's funny how ALL MB con rods seem to be either 145mm or 149mm long.
Regards, Eric

Looks like very much same internals, that I have in my M104. Only my rods are shorter and pistons are little different....

jovani · #2 06-08-2010, 05:19 PM

Any news about the flowtest....?

Joreto · #3 05-25-2010, 07:12 AM

I think the 2.3-16v has the same rod, while the 2.5-16v has different c-c length .

P.S. From what I've learned the c-c length for the 2.5-16v is ~149mm and ~ 145mm for the 2.3-16v. Looks like the difference is that some very early rods (upto 1984 ??)had a 24mm width compared to 22mm with of the later ones

JayRash · #4 05-25-2010, 03:17 PM

well roman claims that the M103 internals can live with 500 hp! i for one can say that 400hp is safe on the internals, if thy arre in good shape, but at this pwr any mistake in the tune will burst any internals. on my M103 the ring broke but non of the internals suffered any damage @abt 11 psi and a bad tune, internals had 390000km+ on them. AND i ended using them in the rebuild (rods and pistons)

MAG58 · #5 05-25-2010, 04:57 PM

You guys are forgetting one major thing between 16v cars and the M103/4. Piston size. 88.5mm in the 3.0L cars, 89.9mm in the 3.2L cars and 95.5mm in the M102's. That's a big difference there. If you notice, from what I've seen on the 16v failures, it's in the center of the beam. That's not a common break from compression, usually you'll see them break at the extremes of the rod near the large end or the small end. This suggests that the extra weight of a piston that's between 5 and 7mm larger in diameter causes the break under tension.

Remember that the compression itself usually does not cause the break but rather the transition at the top or bottom of the cylinder in the change from tension to compression or vise versa that will kill a rod. I've never held a 4cyl piston, but the .98 M104 pistons aren't that weighty for a cast piston and the gutted a bunch out for the .94/.99 pistons which is probably why roman doesn't feel the later 104's are as stout.

M104's are stout little motors, but even like the "legendary" (I hate that term, oh so very much) 2JZ, when you push one and cause detonation, it'll shatter a ring land just like any other motor will.

Just remember that it's usually rev's and piston acceleration, not horsepower, that usually breaks rods. There's a reason that people don't recommend spinning any motor 10krpms and even those that do, don't see their motor lasting forever.

I'll also be willing to bet that a 2.8L M104 will last the longest even at high hp since it can spin higher safely due to a lesser piston acceleration at TDC and BDC.

Joreto · #6 05-26-2010, 08:29 AM

I think I've posted this picture before but here is the broken conrod and like in the volvo the pistons are fine (well except the one on the broken rod). As I posted before damage is due to a seized wastgate (set at 1.4 bars) at a 1/4 mile run so god only knows how high the boost went . BTW the 2.5-16v pistons are not forged like the 2.3-16v ones .

JayRash · #7 08-20-2010, 06:32 AM

the W140 3.0 m104 did make a sweet 231 hp but at slightly lower rpm than its CIS bro
and rev limit was also lower.

400Eric · #8 08-20-2010, 08:18 AM

I would have sworn this engine that I saw was a 3.2.
MAG, what was/is the displacement of the 93 W140 engine that you grabbed? Remember, the fact that it was called a "300SE" doesn't mean much as my M119 W124 is called a "400E" even though it's engine is actually a 4.2.
Regards, Eric

JayRash · #9 08-20-2010, 08:46 AM

eric
one of the early euro W140 had the 3.0 24 but with efi and was called the 300SE

MAG58 · #10 08-20-2010, 11:54 AM

It was a 3.2. Engine code M104.990. They're really easy to tell apart. The metal intake on the 3.2's comes up at about a 30 degree angle before curving back down. The 3.0 heads have intake ports coming almost straight out of the engine. The 3.2/2.8 has a bunch of ribs on the side of the block while the 3.0 look like an M103 and the 3.0 has the water outlet on the side of the head while the 3.2 has it on the front. I don't think there are any 3.0's or 3.2's that don't have these 3 differences.

JayRash · #11 11-15-2010, 06:03 AM

bob can the early 24 valve head with the cis be fitted over the AMG 36 M104 block?
As in do all water / oil passages line up
thanks man ur my best bet on this

Chlippo · #12 11-15-2010, 06:55 PM

Quote:

Originally Posted by JayRash

bob can the early 24 valve head with the cis be fitted over the AMG 36 M104 block?
As in do all water / oil passages line up
thanks man ur my best bet on this

what are you trying to do? what are you aiming for?

400Eric · #13 11-15-2010, 10:28 PM

Jay, I still maintain that the newer head is better. Don't bother with that older head!
Regards, Eric

MAG58 · #14 11-15-2010, 10:53 PM

Ignoring that...

Yes, it should be fine. Only issue you'd run into is that the latter heads use a slider on the tension side while the old heads run a single tensioner wheel that pretty much makes it an M103 timing setup (with a duplex chain) below the head mating surface. That said, you'd have to change water pumps, but the oil and coolant passages should match.

And Eric, I had your crank weights some time ago... I think they're in the hawn-duh connecting rod thread.

JayRash · #15 11-15-2010, 11:10 PM

guys am not doing anything to me AMG.
But i have to admit i like that it stirred such interest

the whole thing is a friend of mine has a W124 300-24 cis and was considering an AMG 3.6 short block thus if the heads do interchange he would save on harnesses and ecus.