M103's- cylinder heads/ Camshafts
 

Good evening,

Whom knows M103 cylinder heads well? I'm looked on line and there is 2.6 & 3.0 liters- open and closed head? There was a change to a chill-hardened camshaft and carbide tiped rocker arms in 89. Makes me wonder as DB must have been trying to save $$- they changed to those in 81' on the OM616/617.
So, I'm guessing no matter how good of condition my 1986 head is, it would be best to install a later model head. Buy one, have it cleaned and rebuilt by a good shop. I say this as besides the camshaft/rocker arm/oil tube changes, it appears in the performance section that the later head is less-prone to pre-ignition.

Then just R&R. I say this as camshaft + rockers from DB is about $1000. I should be able to get a complete used head, valves ground, guides etc for that type of money.
Is there any other changes which need to accompany a changing to a newer combustion chamber design? Injectors? Intake etc?
A 1986 is a no airpump or EGR car. Even it being a Kalifornia car.

Just thinking out loud.

Michael

Sign up for this: https://epc.startekinfo.com/epc/welcome.jsp

It is the FREE EPC from MB. If the chambers changed, chances are the pistons did also.

in this area your knowledge seems vast.....

MB Doc said something about the heads a while back to me when I was getting a spare for my 300SEL. I believe it was not to mix late and early heads for some reason. May want to also drop him a line and ask.

Cams changed over the years, yes. I heard the early M103s had a hotter cam than the later ones.

Also around '89/90 the heads supposedly received better valve guides along with the EGR and Air injection system you know of too.



My question is this: why are you wanting to go through all this hassle? :confused: If it runs fine, drive it.

The heads are the same on all M103's. As the OP said, the only difference is the updated camshaft and rocker design.

The 2.6 and 3.0 heads are the same as well. I asked this question about a month ago.

The change out to different metallurgy was a technical wear problem. There is a TSB out on this.

I believe I'm at the start of the camshaft wear problem...

I my first posting- I mentioned replacement of the cam and rocker for a grand.

I'll give metricmotors a call and see what their spin is on "differences".


Thanks

Any update on this? What did Metric say? If you got a price quote, let us know what they wanted...

:1eye:

Didn't bother them..


I'll just find a head when the need arises which is the later style. There are M013 references that later models take to more ignition advance better than the earlier ones. That says some sort of change if it's piston, EZL etc.
I'll burn that peace pipe when it comes..

M

Not sure all M103 heads are the same. The piston chambers on the early M103 engines were heart shaped (86-89), and the later style chambers are spherical (90-93). I would not intermix the two cylinder heads. But that's just me.

The only thing I follow is to use late rocker arms with late cams, early with early and don't mix them. Also the threads holding the sprocket changed (you don't want to drill and tap the cam on the car when the only sprocket you have won't work:mad:).

Thanks John!

That's what I had suspected...

Correct. You cannot mix early rockers /w later cam and vice versa. It won't work. You must replace it all unfortunately.

I would pay attention to length of bolts holding rocker assy to head. Seems early cars had shorter bolts . Can't remember if later cars had longer bolts or if you had to purchase from MB. Archives has info on this.

Rocker bolt length went from 70mm to 73mm. 75mm will work if you use a bottoming tap.
The oil tube was changed as high RPM operation starves cylinder 1 on early cars. Maybe it is an additional piece, and not a tube change.

M