Cylinder head and valve question

[dnadanny1]

Hi there. I have a 1966 230SL.

There is some erosion happened at my cylinder+ head as showed from the picture. Is it the problem of wrong coolant? any impact from this erosion? How can I fix it?

Second, the 1st cylinder and 6th cylinder intake valves seem at good condition, however, No.2, 3, 4, 5 cylinder intake valves seem burnt as shown in the pictures. What is the cause of it? How can I fix this?

Any comment will be appreciated.

Thanks a lot.

Regards,
Danny

[Cees Klumper]

I am sure more knowledgeable members will comment, but from my limited understanding this erosion was probably caused by incorrect or old coolant. I would explore having aluminium welded in so the original shape can be 're-created'. As for the valves, I would just replacd them (all) with new ones as a wear item.

[ja17]

Good advice from Cees, yes weld and resurface the head if possible. Minimum head thickness is 84mm. Only remove as little as possible. It is normal for the exhaust valves to look a little burnt from the high combustion temperatures. Since the head is off the car it should go to a good machine shop and be totally sis-assembled, re-conditioned and repaired. Plan on new valve guides, seals and a new head and manifold gasket. Most owners choose to use new valves also although the BBB gives specs for determining the condition and re-use of valves depending on condition. Often and new timing chain is installed during this kind of work.

[Benz Dr.]

I'm not going to venture too far out on to a limb but I'd say the coolant used was just plain water. I see this all too often in climates that never freeze. Before you do anything, measure the thickness of the cylinder head - minimum is 84.00 mm. If the thickness is at or below this amount you would be better off looking for another head.

Those corroded areas can be welded back in after all of the corroded material is removed. You will likely have to replace all of the coolant diverters in the head - they should all be available. The small hole in the bottom of the diverter should point towards the valve seat inside of the head.

[dnadanny1]

Thank you all for your information and advice.

I will go ahead to measure the thickness first, before I start welding.

BTW, where is the location of the coolant diverters?

Will let you all know once there is any update.

Thanks again.

Best regards,
Danny

[MikeSimon]

Different questions for the experts:
As I am still trying to sort out some mysteries around the cylinder head on my 280SL, I see the head surface on this 230SL looks very similar to the one on my SL.
In particular: The head has a "combustion chamber" only around the exhaust valve. The area around the intake valve is not recessed. Is this typical for SL heads?
I have seen other cylinder heads supposed to be for 280 fuel injection applications that have a recess around the intake valve also. What are they for?

[ja17]

No recess is normal on a 280 head with 9.3. or 9.5 compression. Lower compression ratios have more recess in the head.

[MikeSimon]

No recess is normal on a 280 head with 9.3. or 9.5 compression. Lower compression ratios have more recess in the head.

Joe: This is part of the mystery! I think I posted about that before. My head says it has a 9.0 compression. It has no recess and it is definitely a SL head. I have seen others that said 9.5 and had a recess. Never seen a 9.3, though, (with or without recess).

And here is another example of a head with low compression and no recess, albeit this is not a fuel injection head.
So, I don't think the recession around the intake valve has anything to do with the compression. And if even you don't know a definite answer, I have no hope finding one here.

[Tyler S]

Mike, Measure the head thickness. Heads that have been cut .3mm or more loose the recess area between the valves. Here is a before and after machining of my cylinder head.

[dnadanny1]

HI all.

The number of my cylinder head is 1270161901.
1270101620 and 1270101520 which is the most suitable for replacement of my cylinder head?

Thanks a lot.

Regards,
Danny

[ja17]

Mike, are you sure your are not just seeing discoloration from combustion and no actual recess?

[MikeSimon]

Joe: Thank you again. The recess is not just discoloration. I have the heads in my hands and it is definitely a recess. I was thinking of the appearance after machining also and it would explain why heads that originally had a recess do not have one. It does not explain why heads that should NOT have a recess, like 130 016 11 01 have one. My quest for an explanation will have to go on and I may never find the answer.