Does a 250SE head work on a 230SL?

[hughet]

Will a 250 SE head work on a 230 SL? I understand that they use the same head gaskets but are there any other differences?
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&rd=1,1&item=4560630819&sspagename=STRK%3AMEWA%3AIT

[Naj ✝︎]

Yes, a complete 250 SE head will fit a 230 SL engine.
However, the 230SL has a hotter camshaft and you may want to reuse it, complete with its bearings.

naj

65 230SL
68 280SL

[ja17]

Hello,
Yes the 250SE head will work fine. It has some upgrades over the 230SL head. Using the 230SL camshaft will give you a bit more hp as Naj has mentioned. You may have to keep the camstands with its camshaft. Be sure to check the length of the head bolts different configurations of camstands may require their different length head bolts.

Joe Alexander
Blacklick, Ohio

[JimVillers]

I would expect the 250 head would lower the compression of the 230 engine.  The compression ratio is the ratio of the pistion sweep volume to the combustion chamber volume.  The 250 head would have a larger chamber volume and thus would lower the compression ratio.

Jim Villers
190SL, 230SL 5-Speed, 190E 2.3-16 Kompressor

[ja17]

Hello Jim,
Interesting obsevation. However since most 230SLs have a 9.3 compression ratio and the 250SLs have a 9.5, the compression should be about the same after the switch. It appears that Mercedes may have left the combustion chambers in the head the same. They just pumped more volume into the same space with the 2.5 litre engine which raised the compression to 9.5?


Download Attachment: Cyl head chart Joe A 4-04.JPG
52.14 KB

Joe Alexander
Blacklick, Ohio

[mbzse]

quote:Originally posted by ja17

It appears that Mercedes may have left the combustion chambers in the head the same. They just pumped more volume into the same space with the 2.5 litre engine which raised the compression to 9.5?

Well, not quite the same. Literature gives the volume of the combustion chamber for M127 (230SL) head to be 45,3 to 48cc, whereas M129 (250SE/SL) volume is 48,0 to 50,7cc.  Nominal compression is 9,5:1 for both engine types.

/Hans in Stockholm

[ja17]

Hello Hans,
Thanks for the additional information. There must be more than one version cylinder head for the 230SL. I have several here stamped with 9.3 compression. Maybe the current versions available from MB are all 9.5. If you look at the cylinder head chart we have identified at least four cylinder heads for the 230SL.
It would be interesting to research which heads are available new for the 230SL and 250SL at this time and if they are the same part?

Joe Alexander
Blacklick, Ohio

[mdsalemi]

quote:Originally posted by hughet

Will a 250 SE head work on a 230 SL? I understand that they use the same head gaskets but are there any other differences?
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&rd=1,1&item=4560630819&sspagename=STRK%3AMEWA%3AIT

Hans,

With all due respect to Joe and others in our group, you should pose this question to Mike Elias at Metric Motors, or to Noel's.  Metric is in California, and Noel's is in Florida.  You can find these guys via STAR advertisements, or on an internet search.

The ONLY thing that these two companies do is to REBUILD Mercedes engines.  My guess is that they'll know what works and what doesn't and any changes.

Michael Salemi
1969 280SL
Signal Red w/Black Leather
Restored

[Benz Dr.]

230 and 250SL's have the same bore size so the heads can be interchanged. The extra cc's are obtained by the longer stroke of the 250 engine.
Compression is produced by how far the pistons protrude out of the block and the size of the cumbustion chamber. The 230's that I've seen all have 9.3 heads which is standard I believe.
On my engine ( 250 ) for the Red Rocket, I milled the top of the block about '030'' which gave me another 30 PSI, so I suppose each .001'' gives another pound of compression. The pistons are just level with the parting surface with some of them a few thousands more. Those cylinders have a few more pounds of compression but they average about 175 - 180 PSI. What I found was the max oversize pistons are shorter and so I had to deck the block or have 150 PSI compression.
The longer stroke of the 250 engine gives you more displacement and torque but not that much more HP. If you use the cam, distributor and manifolds from the early 230 on a 250 then you start to see something.

Dan Caron's
 SL Barn
benzbarn@ebtech.net
 slbarn.mbz.org

[JimVillers]

Very interesting discussion.  

Dan ... Oversized pistons are made in a manner to retain the same compression ratio.  With the increase piston diameter and the increased piston sweep volume, the pistions are either shaved on the crown or in the case of my 2.3-16 pistions, dished to lower the compression.  

Manuals can always be incorrect, but my manual has the 250SL, the 250SL and the 230SL with a compression ration of 9.5:



Jim Villers
190SL, 230SL 5-Speed, 190E 2.3-16 Kompressor

[Ben]

My part supplier told me there were three or four different pistons available for the 230SL in each oversize !

I was told to measure the compression height, the distance from centre of gudgeon pin to the crown, to ensure correct parts arrived !

Dan.......you've mentioned before that there is very small clearance between piston and valve at some point in the cycle, if you had say a 250 engine with high compression pistons,a milled head and 230SL cam would you get contact......................or just a bit more power ??

Regards,
Ben in Ireland.
'64 230SL 4sp.

[hughet]

This has turned into an interesting discussion! especially in view of the fact that when I first got my 230SL 17 years ago unleaded gas was disappearing and I was afraid that the quality of gasoline would be such that I would need to lower the compression ratio or start buying additives.

I had just come off of a rebuild of a 66 Jaguar e-type where I used 8:1 low dome pistons like they were using in the sedans in place of the 9:1 high dome pistons that came in the car. It worked out very well. The 4.2 Jags came tweaked up to 265 horsepower and de tuning them from 9:1 to 8:1 only resulted in a loss of 20 HP and made them easier to tune. Jaguar even had a flattop piston that get you down to 7:1 if you wanted a Jag but lived in the colonies!

At that time Mercedes varied compression ratios by installing different thicknesses of head gaskets. They had thick gaskets to kick down the compression to 8:1 for underdeveloped countries where you could only buy 85 octane gas and regular ones for the USA and Europe where the fuel quality was higher. I decided not to do it because the thick gasket was a special order item and the car really doesn't have an abundance of power anyway.

I need a head because I can no longer adjust my valves and I am afraid to speculate about whether my core is good enough to rebuild. If I go with this head how low will the compression be considering a shorter stroke and larger chamber?

As an interesting side note, my car came with a "Mercedes-Benz Service Amerika" book listing all of the service locations in North and South America in 1964. I am looking at it now and I see that the first page for each country lists the quality of fuel available there. For example, regular gas in Argentina was 76 octane and premium was 86. 72 and 83 in Uruguay. 68 and 75 in Bolivia. Yikes! Do any of you have this book? It would be very handy for time travelers.

[mbzse]

quote:Originally posted by Joe A (ja17)

Hello Hans,
Thanks for the additional information. There must be more than one version cylinder head for the 230SL. I have several here stamped with 9.3 compression. If you look at the cylinder head chart we have identified at least four cylinder heads for the 230SL.

 I was quoting from the M-B Book of tables 1966 ed. Now, I note that the 1969 ed. does _not_ give the combustion chamber volume..? I also see the 1969 ed gives reference to a 9,3:1 version 230SL (M127) head. Hmm, interesting, we learn together here...

/Hans in Stockholm

[Benz Dr.]

There are at least 3 different 230SL pistons. Early ones have 4 rings while later ones have 3 rings and a larger piston pin. Early conceting rods are drilled to oil the piston pin while all others are not. There's also a low compression piston that has a milled area on the top.
Standard pistons are flat on top but may be different thickness from the piston pin hole. NEVER mill the head to increase CR. You can have up to .015'' of piston height above the parting surface of the block but just level is probably best for most engines. The clearance between intake valve and piston is taken at 5 degrees ATDC on the power stroke. You need about .035'' minimum or the valve could hit the piston once deposits form after a few years of running.
I can't remember how this goes but I think that long stroke with large bore gives you lots of torque at low RPMs but not much HP.
 Short stroke with small bore gives you lots of HP with low torque which is what we see in 113's.
My farm tractor produces 155 HP at 2,200 RPM but will pull a plough with 5  16 inch bottoms ( 6 1/2 feet wide ) through heavy clay soils at about 6 MPH. That's torque!

Think of a super tanker. 3 foot piston diameter, 3 foot stroke and maybe 40 RPM.
Think of an F1 racer. 2'' piston 1'' stroke 19,000 RPM.

Dan Caron's
 SL Barn
benzbarn@ebtech.net
 slbarn.mbz.org

[Ben]

All good info Dan !

My understanding is that long stroke gives good torque and flexibility but its not good for high RPM's due to the inertia whilst short stroke and large bore is what gives all that high end HP but poor torque !

These are described as over square or under square engines !

Regards,
Ben in Ireland.
'64 230SL 4sp.

[A Dalton]

A simple analogy..
Torque at the crank center  is increased as the rods center line distance  from the center of a crank[ radius]increases.
 Same as you put a cheater bar on a wrench to break those nasty lug bolts. If you grab your 12" lug wrench  and apply 100lbs pressue , your lugs don't move .. but you know they will move real easy with a 28" longer lever [cheater bar]. You have not changed the applied force, but have increased the torque force to break the lug nut by lengthening the lever.
So, if the stroke is long, the same force will have more torque than if the stroke is short.
That's why a 2 lunger John Deere will pull a stump and your 283 Chevy won't..but your 283 will blow the doors off your tractor at a light..
 I use the 283 eng as a comparision b/c their fame came from being one of the first big bore/short stroke automobile engines to be put into a common , production car ..
The Ford guys didn't know what happened at the drag races !!!!!