In thinking about it.. the type PC is determined by the piston top configuration ..
So did you shim the PC to take care of that ' little' interference ? If you did it would then be normal for you to need to ream the gp hole for it to fit perfectly...

I'll print all this out and go talk to my favorite machinist about it.

I believe MB Doc said if you changed prechambers it would work.

Tom, for those of us who are not lucky enough to have a ' favorite machinist ' available... how about posting his contact information ? LOL
I do not know what is wrong.. I am just trying to square OP descriptions with standard FSM instructions and hoping to accidentally ring someone's bell...

No, I had the interference with the W123 later 1983 pc. I measured these with the 1974 pc and all was identical except for the nozzle. The 83 nozzles were about .050 longer which is what caused the interference so the 74 pc were installed. What is puzzeling, the 83 and 74 240s both have the same pistons. This tells me that something else is different. Whether it be deck height, head height in relation to the piston, ect. It seems the cam is now lower in relation to the crank which would in turn shorten the drive portion of the chain which would advance the ip when the chain tensioner took up the slack. I don't know if this little bit of advance would cause this high idle, but we will see when I do the drip test.

Thanks a ton.

The later pistons should be .10mm smaller if I remember right.

Homer Banes
Banes Automotive Machine shop
Earl Avenue
Lafayette Indiana
765 449 8551

He is a great machinist with a very very well equipped shop. He is unintimidated by any motor from flathead lawn mower to v12 Ferrari. If the parts are available and a book to tell you the specs, he can rebuild it. He is honest and charges reasonable prices. He (like me) can get a little cranky if you piss him off and has been known to refuse to work on peoples stuff if they are too difficult to deal with, but if you are a normal person with reasonable expectations he can fix it for you at a reasonable price.

I have had him work on Saabs, Caddies, Mercedes, Ferrari, and Chevy motors all with great success. About twenty years ago he redid the motor in my 82 300TD and the next day I put my Mrs. and two of my kids in it and they took off for New Orleans. No problem.

He is almost exactly the same age as me and his son is following quickly in his footsteps. Homer says that Todd is better than Homer now on certain things.


I printed this thread out and we talked it over this evening. ONly thing we can think of is ip timing off. If the chain can drop off the crank you could be together with the crank and cam and be off on the ip even though the ip never lost its grip on the chain.

I don't get how the cam can be closer to the head if you used the cam and cam towers from your engine.

Tom , I was sorta kidding ... thinking you would not share that info... I will put that into my address book for sure.

So you are saying he is the machinist equivalent of the Seinfeld " Soup Nazi " ? LOL
Everyone should follow certain " normal " rules anyway...

I agree that the cam position is not changed or the problem.

Since the ' beginning of start' on the fuel is pretty easy to determine I suggest that be next on the list. The FSM is very sincere about keeping tension on the chain when rolling in a new one... and looking at the crank will not show the problem until the engine is started and the tensioner gets oil pressure.

That explains why they hit! I was under the impression they were the same. That thought process led me to all sorts of crazy ideas. Coupled with the crazy ones I already had....:rolleyes:

With milling the head, it has to be a little closer, the same as the cut amount.

The little I know about the tolerances in the MBZ, I thought that may be the culprit.

Multi quote isn't working for me, so sorry about the multi posting. Thanks for all of the sincere help. I will get either an old injector tube or a drip tube and take care of this this weekend. I will let you all know what I find.

Carl

There were two sizes of piston diameter in the 240... the smaller was the later to fit with the tax structure in Europe... so the size displacement was made smaller to cost less in taxes...
There was a change in the compression ratio from 21 to 21.5 I believe at some point... but will have to look at the FSM to be more specific.

For the record... the number one piston is a different diameter than the other three..
AND there was the change in the total displacement by reducing the bore sizes...

The engine getting enough fuel to idle very high is not a head or timing problem I believe. Especially since you apparently can restore normal idle conditions by manipulation of the pump lever with the linkage disconnected. I have got that right? It seems to me that if the linkage duplicated the same position you establish by hand the idle should be the same.

If the 76 has the linked flap in the intake manifold it might bear some attention to make sure the function is there. Basically what I am still missing is why by hand on a disconected linkage do you get a normal idle but not when the linkage is hooked up?

This alone tends to eliminate any head or timing effect in my mind. Yet I might be missing something is a possibility. Is the butterfly linkage disconected at the same time? Do you even have the butterfly on a 1976 engine? I have never worked around one of those.

The small amount of increased compression if there indicates at worse the timing may be a little ahead. This in itself would not up the idle like you are experiencing in my opinion.

Or even if it did then the manual manipulation of the injection pump lever would not stop it. If your description is correct you are looking for what is different between linkage hooked up and hand manipulation of the lever. Is the lever bearing sound? Side play on the shaft present?

Manual manipulation of the idle speed brings up that little knob on the dash for some cars...
often they are broken or do not seem to work...but could that be messing with the idle situation ?
This feature was built into the design to compensate for wear later on ...is my understanding... so many don't use it, need it , or know about it until decades later when it has been sitting too long to work without lubrication , etc...

I don't see how IP timing could do this. Fuel delivery is regulated by the ALDA and the throttle lever. If just moving the IP timing can increase RPM without adding more fuel, then you've found a more efficient timing position for the IP than the factory specified position.

I believe the only cause for this is you are giving the engine more fuel somehow.