M103 heads

[gschira]

Just curios--Does anyone have pics of the two different heads and piston tops? Also, what is a squish pad? Would be helpful if it were pointed out in a picture.
Could one of those oddball assemblies be a 2.6 head on a 3.0 engine? I mean I have the bigger bore block but maybe the oddball head. I thought I had an original build '88 300 SE, but after reading posts on this forum (M103 2.6 and 3.0L head differences?) I am beginning to wonder. Could someone clear this up for me. It ran great until a cam bearing/tower stripped out of head.
Thanks and have a great weekend.............

[JohnM.]

The 86-89 M103 engines had issues with cam/rocker hardness and also the towers stripping out which is consistent with the model year of your car. So your head is most likely original. It doesn't make sense to swap heads on these cars because they can be fully rebuilt very easily...unless it's warped extremely badly which is rare.

Squish pad, quench, piston/head clearance, is the area between the flat part of top of the piston and the flat part of the block (combustion chamber). You have no reason to worry about it.

The only thing that changed on M103 heads was the style (shape) of the combustion chamber which should not have any affect on the squish area. But it did change compression *slightly*. I can't find pictures of a early vs late head, but it doesn't really matter. Have your original head rebuilt at a competent machine shop and you'll be back on the road.

[gschira]

Thanks John, but what does this quote by duxthe1 mean---"Yes the head will bolt but the 2.6 head has a squish pad and the 3.0 is an open hemispherical chamber. So a 3.0 head on a 2.6 would have a lot less compression. FWIW, there may be a few oddball assemblies out there but AFIK... no dice."
My head does not have a totally open hemispherical chamber.
Should there be clearance indents for valves on piston tops for 3.0 pistons? Pics would sure be nice. Anyone got pics? I will post some soon...........

[gschira]

Ok, which head is this ---2.6 or 3.0 ???

[JohnM.]

Originally Posted by gschira

Ok, which head is this ---2.6 or 3.0 ???

Both


EDIT - I switched them sorry.

That is actually a early head with the heart shaped chamber (86-89). So both a early 190E and early 300E use that head.

The late heads had a hemispherical shaped chamber. (90-92)

[gschira]

Thanks John M for clearing that up for me.........

[RdSnake]

What was Mercedes' reason for changing the combustion chamber design?
Did they also change compression ratio between the 2 designs?

[Dr. Sternschnuppe]

Originally Posted by RdSnake

Did they also change compression ratio between the 2 designs?

No, they didn't change CR.

[Ivanerrol]

M.B. changed the metallurgy of the head components due to premature wear problems.
Around 1989.
If you are going to rebuild the head then the newer compound materials will be in the new moving and bearing components.

This was also the era when unleaded fuel and catalytic converters were slowly being introduced worldwide so this "may" have an had an impact on the design of the combustion chambers.