Piston ring fitment

[bigmellon]

I am working on getting my M130 long block back together after having parts at the machine shop for far too long!!  I am getting everything laid out and prepared and came to a screaching halt when I got to the new ring set...

removing the old rings was a real bear.  I am not entirely sure I can get the new piston rings on without distorting them in some fashion.  Is there a secret to do this properly?  As usual MB seems to have a tool for everything - http://www.samstagsales.com/mercedes/mb000589373700.jpg  Do I need this?  Any advice on sliding these puppies on?

Also, is there a spec for the ring gap?  I am assuming I need to file fit the rings. 

Any help on these two topics would be excellent!!  I searched and searched on this forum.  Next stop Google! 

-Kyle

[ja17]

Hello Kyle,

The generic ring expander tool will work fine. Try Napa or Autozone, they are inexpensive. Clean the carbon out of the ring grooves.  The ring gap clearance is .004" per every inch of piston diameter. (eg. a 3.0" piston would be  .004" X 3.0" ).

If the cylinders are not being bored to a new szie, make sure you de-glaze the cylinder walls well. If the cylinders are worn too much, re-ringing the engine will only give you an oil burner.

[bigmellon]

Picked up the ring expander tool this AM!!

Thanks for the pointers Joe! Now, I am off to work!! 

[Benz Dr.]

But do you know where to put the ring gaps?

[glenn]

What's the answer?  Equal spreads around 360?  90 degrees for four rings?  120 degrees for 3 rings?  IMWTK

[Benz Dr.]

With four rings you start with the top ring.
1st ring dead centre over the piston skirt
2nd ring over the piston skirt 180 degrees from the first one
3rd ring 90 degrees from the 2nd ring over the piston pin
4th ring 180 degrees from the 3 rd ring over the piston pin

Oil the ring grooves after you get the rings installed and spin the rings several times to work the oil in. Make sure you have the small notches for the rod bearings facing towards the left or distributor side of the engine with the arrow pointing forward on the piston.

[ja17]

Good advice Dan,

I have seen some of the factory service manuals say to position the numbers on the rods to the left. Well there are stamped numbers on one side and light electrically etched numbers on the other side. If you put the stamped numbers on the left the rods will  be in backwards.  Your advice to put the bearing notch on the distributor side is the best way to make sure they are in right!

[Benz Dr.]

The BB book doesn't tell you how to set the rings. In fact it doesn't tell you a lot of things. These books weren't made for your average Joe ( pardon the pun ) and I'm sure they expect you to already know how to do these things.
What the book WILL tell you is all things that pertain only to this car or engine. If it really doesn't say, your best bet is to go back in years until you find what you need. In this case, I actually went back to the 190 sedan work shop manual - probably one of the best books they ever made. It tells you everything you need to know and in fairly good detail. I use that book for doing king pins - it's by far the best resource.