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  #1  
Old 09-17-2018, 01:59 PM
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Location: South NJ
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M104.990 Block with M104.981 Cylinder Head

During the disassembly of the M104.981 from my 129 I discovered that the block is damaged and can not be used. After I cried a little an idea came to mind: I have a low mileage M104.990 from a w140. Id like to use the block from the .990 while keeping the KE-jet in place using the .981 head and intake manifold.

I've done some research and this is what I found:

1. I will have to use the M104.981 oil pan in order for it to fit in the 129 thus I will have to use the .981 oil pump as well

2. I will need the M104.981 water pump as the .981 head does not have the front cooling port

3. I will need to use the .981 timing chain.

Now,

Assuming the head will bolt to the block..

Which headgasket to use?

I will appreciate any input
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  #2  
Old 09-17-2018, 04:31 PM
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I'd look really hard into using the complete W140 engine / FI system. K jet is $$$ when it starts to fail.

Your conversion info sounds correct but I can't offer any verification.

What is wrong with the old block? Cylinders can be resleeved if you have a bad hole.

For a head gasket I'd use one that matches the bore size. ( the newer motor ) but would compare coolant holes to be sure it matches the older engine. ( Since you are using the older water pump. )
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  #3  
Old 09-18-2018, 08:56 AM
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Thanks to MAG58, Thing are a bit more clear.


It looks like my two main "issues" are the timing configuration and the knock sensing.

I would like to use the timing setup from the M104.981, according to MAG58 (and looking at each motor's guides) I might have to transfer some guide pins, I wonder if someone can make that even more clear..


The block harmonics are different between the two (WIS article). Per WIS one should match the according EZL to the block used ("except for USA" , prehaps we did not get early models?) , I will have to use the sensors from the .990 but since I am using the .981 EZL, I am not sure it will function and control the knock. I prefer not to use the .990 EZL as it will not communicate with the CIS controller.

I like the KE-jet system, parts are $$$ but once a system has been refreshed and "tuned" it can functions flawlessly.


I believe that this engine (once assembled and actually works) will be a good alternative in the future as M104.980/981 will disappear. Trying to get a set of .980 pistons today (standard or oversized) is a huge expense.


As always I will appreciate any further input.









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  #4  
Old 09-18-2018, 07:50 PM
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So are you moving forward with the plan?
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Past mb: '73 450sl, '81 280slc stick, '71 250, '72 250c, '70 250c, '79 280sl, '73 450sl, parted: '75 240d stick, '69 280s, '73 450slc, '72 450sl,
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  #5  
Old 09-18-2018, 11:11 PM
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Do we know what AMG did to CIS when they took a 3.0 24 valve to a larger displacement?

I'd be concerned that the computer / CIS air intake funnel won't be able to cope with , an admittedly, small displacement increase. The shape of the CIS funnel dictates fuel curve in open loop with the computer trimming fuel in closed loop.
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  #6  
Old 09-20-2018, 12:12 AM
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Join Date: Mar 2018
Posts: 47
stock pistons

if stock pistons are what your looking for, i have a set i can sell you
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  #7  
Old 09-20-2018, 09:46 AM
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I have plenty of M104.980 blocks and internals including a first/second oversized pistons sets. I’d like to avoid using a .980 block as I’d like to upgrade.
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  #8  
Old 09-20-2018, 05:38 PM
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Upgrade to what? You are really making things more difficult for about zero gain.

In the end you are ending up with a 3.0 - 24 head on a 3.2 block. If you want more displacement, have the 3.0 - 24 block's bores sonic checked. If it passes, bore to fit the 3.2 pistons.
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