Cylinder Heads

[MikeSimon]

Back to my favorite subject
After doing a lot of investigation and getting the cylinder head for my 1971 280SL ready to go back on the motor, I came about this sale of a 230SL on BaT. If I recall, the seller claimed it was a "high performance" option to put a 250 head on a 280 block. Can't really see how that works. The car may start and run, O.K., but for how long reliable? Any opinions from anyone?

https://bringatrailer.com/listing/1965-mercedes-benz-230sl-41/?utm_source=transactionalemail&utm_medium=email&utm_campaign=bat_tagged_comment#comment-10097430

[ja17]

I know a 250SL/SE head is an improvement and will work fine on a 230SL block, but never heard of putting a 250SL/SE head on a 280?

[rwmastel]

Back to my favorite subject
If I recall, the seller claimed it was a "high performance" option to put a 250 head on a 280 block.

The word "performance" does not appear in that ad.  Can you point out this claim?

[MikeSimon]

The word "performance" does not appear in that ad.  Can you point out this claim?

The statement appeared in the comment section and it was not made by the seller. I guess the seller quite wisely did not make any comments regarding the head/block issue

I was advised previously by a fellow that raced a 113 out of the Houston area that one of the competitive combinations for the 113 series was a 280 block with a 250SE head combined with the early style steel headers and a Euro cam. Since one of my 113’s was already a FrankenBenz, I had a motor built as such. Fingers X’d, but thus far it’s survived 2 cross country trips and is materially quicker than its original engine.

[rwmastel]

Yeah, I searched comments. I specifically searched "performance" and didn't find it, obviously.

Interesting statement by that guy.

[DaveB]

Yeah it is interesting. One of the other commenters suggests the mismatch between the 86mm bore block and the 82mm head might cause problems, but the ‘two cross-country trips’ seems to negate that.
Wouldn’t that combination make a very high compression ratio? And conversely (question for Joe, or anyone) if the 250 head on a 230 block lowers compression, is that combination really a significant improvement?

[MikeSimon]

Owning a 280SL which used two different M130 blocks and consequently two different heads, I would be more concerned about the correct match of cooling passages. Which is an issue with the 2.8L

[Benz Dr.]

Yeah it is interesting. One of the other commenters suggests the mismatch between the 86mm bore block and the 82mm head might cause problems, but the ‘two cross-country trips’ seems to negate that.
Wouldn’t that combination make a very high compression ratio? And conversely (question for Joe, or anyone) if the 250 head on a 230 block lowers compression, is that combination really a significant improvement?

The improvements are concentrated around the valves on a 250. The 230 and 250 blocks employ the same bore but the stroke is longer on the 250. A good 250 engine should produce about 165 - 175 PSI while optimal compression numbers with a bit less for a typical 230 engine. So I would conclude that a 250 head would be a small improvement.

[Guanaja]

testing

[Benz Dr.]

When you buy new pistons they will be slightly shorter than the stock units you removed. This is done to compensate for the slight increase in compression ratio from increasing the bore size.
I've looked at this as lowering the compression ratio on our engines to below normal amounts resulting in a performance loss.
 The pistons should be at least level with, or slightly proud of the parting surface, by .010 - 020'' This can be accomplished by decking the top of the block to obtain the desired piston protrusion. This is a sure way to increase performance but piston to intake valve clearance must be strictly observed.

You can't switch early and late cylinder heads on a 280SE engine or you will have a gasket failure. Compare a 250 head gasket to an early 280 and see if they're different. 

[bracurrie]

To me this is a bizarre discussion . Whatever the possible gains why compromise possible drive-ability.  A higher compression would require fuel that would be hard to get. A lower compression would not result in higher performance (yes, I did stay at a Holiday Inn).
I am sensitive to this discussion because I just bought a new head for my M130.980. I am blown away that they are available from Mercedes.
Brad

[Benz Dr.]

To me this is a bizarre discussion . Whatever the possible gains why compromise possible drive-ability.  A higher compression would require fuel that would be hard to get. A lower compression would not result in higher performance (yes, I did stay at a Holiday Inn).
I am sensitive to this discussion because I just bought a new head for my M130.980. I am blown away that they are available from Mercedes.
Brad

I wouldn't worry too much. 91 or 92 octane will work well on a 9.5 cylinder head.

[MikeSimon]

I am sure, later heads had only 9.0:1. Mercedes for some reason, at least here in the US did not want to admit to that and removed the embossed compression mark from the head. I have a head in my possession original from a 1971 280SL that says 9.0 on it.