Pistons, Compression, Head Issues

[n/a]

280SL now out and apart, have located all parts including the 87.5 2nd overside pistons,as there is much wear on thrust side of bores.Pistons located are 130.030.9117 so far nobody knows anything about these except they are supposed to fit..NOW...what I am told I am working with is a emission late 71-72 service replacement block..as someone mentioned before the pistons at TDC should stick out of the block half of the thickness of the head gasket which creates the quench area for this style head and gives a 9.5 compression ratio...my engine pistons are down the bore .044 (1.1mm) and gives approx. 8.5 compression...I know I can deck the block by milling approx .034 off the deck to give me some semblence of original compression of probably 9.1, the question is I also know from reading here an offset key can be obtained for the setting of cam timing,,BUT what about all the slack in the timing chain, I know the tensioner will pull this up...BUT is it satisfactory???...also the water pump and clutch fan is shot,guides are tight in bores but will be replaced with Std guides..the head gasket is # 252131 again nobody knows if that is early or Late style. also the cam in the motor is an 05 and will be replace with the 08 I now have...any help would be appreciated...I have emailed Mahle in Germany with no response so far..thanx

[n/a]

The pistons mentioned above fit the 1970-71 verson engine. The cams you mention are not interchangeable. The head gasket for the later engine has "egg-shaped" combustion chamber areas, and the early has "straight". The early head shouldn't be used on the late block. The "08" cam is also for the early engine, and the cam bearings won't interchange with these 2 cams. So many changes. Contact me with any questions. hanson_anaheim@mbretailer.com .

tom in CA

[Cees Klumper]

Replacement blocks can be somewhat tricky ... the engine Joe Alexander and I rebuilt last summer was a replacement engine that was manufactured I believe somewhere in 1971 or 1972, but it featured the old style head that Tom is referring to, but had the later style crankshaft bearings (which had an improved design). Looks like they supplied late-style short blocks that would fit with the earlier style heads.
Decking the block to achieve standard compression does not sound like the right way to go to me, but I will gladly defer to what Joe can comment about this.

Cees Klumper in Amsterdam
'69 white 280 SL automatic

[ja17]

Hello 71280SL, Cees and Tom H.,
Lots of complex questions here. It is not that difficult to figure out what the factory did originally. The difficult part is finding out what they did the thirty years since! As Cees and I came to realize last summer, It seems that they make improvements and revisions on the design of replacement parts for years after the model has gone out of production! Even if you have access to all factory literature, service bulletins, dealer only literature etc. you could not possibly keep up with  avalanche of updates changes and redesigns, of all the parts on all the models. Tom Hanson is always of great benefit to us here. There are not many Dealer Parts People like himself interested in helping out in these areas.

Here are some of my thoughts; the M130 engine compression is usually the function of the cylinder head from the factory. This is why the compression ratio is cast on the cylinder head. The standard cylinder head for the M130 engine is 9.5 to 1 (high compression). A low compression engine could be ordered which had a low copression cylinder head. These heads had a different part number and a lower compression ratio cast onto the head.
High octgane (95 octane and above) fuels became increasingly difficult to find in the modern non-leaded fuels so I SUSPECT some low compression pistons became available for these engines in later years? This would prove more economical than replacing the high compression cylinder head to lower compression.
In addition, different OEM manufacturers of pistons may have changed the construction or design of the parts over the years. Mercedes may assign different part numbers to these versions.
One thing is for sure. The standard M130 engine was high compression and USA and Euro versions had the same compression. These heads should have 9.5 cast on them. Earlier W113 cars (230-SL) had slightly lower compression (9.3), and lower compression heads were available for these models also. I have seen at least three original different configurations of the standard M130 (280-SL)pistons for the 9.5 to 1 engine. Some have flat tops (original design) some have stepped tops (later design) some have three rings some have four rings some have a large groove between the 2nd and 3rd ring some have none. They all gave the same results 9.5 to 1 compression. They were manufactured at different times with different designs some times by different OEM manufacturers. I have never ordered or even looked for any low compression pistons for these cars. I can't say that they even exist.
New pistons ordered for your engine should be for the standard 9.5 to 1 version unless specified otherwise. Check your cylinder head number and compression ratio on the head if in doubt.
I am going to bring up my old cylinder head string and will add some relevant information to it for you Don. This way this  head information will stay in a string together with other head information. I will take some photos of the early and late combustion chambers and head gaskets and pistons and post them also. We will hit your other unanswered questions along the way. Stay tuned!



Joe Alexander
Blacklick, Ohio

[ja17]

Hello 71280-SL
Here is a photo of the early and late version M130 (280-SL) head gaskets for the 9.5 compression heads. They are not interchangable. The late version "oval" combustion chamber head gasket is on the left and the early version "square combustion chamber is on the right. Notice how close the cylinders are together! Do not oveheat these engines.

Download Attachment: Head gaskets M130 engines.JPG
40.57 KB

Joe Alexander
Blacklick, Ohio

[Benz Dr.]

Tom's quite right on this one. The heads, blocks and cams are all different between early ( up to mid way in 1969) and late engines.
 Stepped pistons are lower compression I believe. I ended up with a set of these for a 230SL last year and it just wouldn't make high compression. I've seen 230SL's that were rocket ships with up around 165 PSI but this one was dead even at 140. At least he can run regular in it.
I also believe that max over size pistons are shorter above the pins. This would be consistant with the piston being too low in the bore at TDC. The reason for this is that it's expected that both the head and the block will have been milled somewhere along the way so they give you pistons with reduced crown hieght to prevent the valves from hitting the pistons. Decking the block may be your only option. I put new pistons in my car (Red Rocket) last year and everything was perfect and it still was only about 145PSI. These pistons sit down in the block too far. NEVER cut the head for any reason unless needed. Blocks you can get but heads are twice as much in used condition.
Cutting this much will affect valve timing. Moving one tooth on the cam is equal to 18 degrees on the crank. The important thing is to have .9 mm between the intake valve and piston at 5 degrees ATDC on compression/power stroke. This is where the intake valve and piston come into cose contact so you need to find the highest valve in the head and check that one. You need a dial gauge set on the valve spring retainer while you push the valve down. I put a light spring in place of the regular spring so I can push it down by hand. This is also easier when timing the cam to the engine. Once I have it set up I replace these  valve springs and then install all the rockers after I have oil pressure. ( remove the head to replace these  springs - it's only placed on the block and not screwd down very much)

regards,

Dan c

Daniel G Caron

[n/a]

"can of worms"...bought 08 cam when old one lost two lobes...can I now change cam towers and bearings to use this cam?.you folks have just posted MORE INFO than I have been able to find in the entire year. thanx...here is what I am dealing with here now that we have some pros looking on...block marked ONLY 24D-74 and 130.011.1401, pistons are flat top marked std #89, rod 48mm stanped bearing marked 4-74 pn 114.0711, main 59.1mm bearing stamped 1-74 pn 130.0802, head marked 130.016.3201 280 SE/A NO compression mentioned anywhere, cam #05  114.051.0101, I am told the pistons I am about to buy are FLAT TOPS #130.030.9117 I figured we would install one after boring and find out where deck height is and then DECK Block a nominal amount to bring piston somewhere near the top of block so as to not lose too much compression but this all depends on the compression height of the new pistons. again thanx all.

[Ben]

When I ordered the 1st oversize pistons for my '64 230SL the dealer asked me for the compression height as in the distance from the centre of the gudgeon pin to the top.

I was told they needed this as there was so many variances. What I got was exactly the same, 4 rings, but in 82.46 diameter made by Mahle in lovely little Mercedes boxes. They cost €110 each !

Merediths book shows various changes !

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

[ja17]

Hello 71280-SL,
The bad camshaft could have very well been the source of your low compression. If an intake lobe is worn the engine cannot pull in a full charge of air to compress. By chance was the bad cylinder the one with the bad camshaft lobes?
A race shop can calculate the volume of a cylinder and combustion chamber to give you the exact compression. They measure in cubic centimeters the displacement with a liquid. This can be done while the engine is apart. More to come, out of time right now.

Joe Alexander
Blacklick, Ohio

[n/a]

Gent's, my name is Jamie and I'm doing the work on '71's car.  Having a good time at it in spite of MB's lack of info on parts.  This project is pretty mysterious, as I took it apart it was obvious it had been apart before.  Find a difficult bolt to remove and the head was already rounded off. :0  Bolts with different torque all around.  Couldn't tell where the motor was leaking, because it was covered in grime and oil up to 1/4" thick on the oil pan.  The auto trans had it's life blood dripping on the garage floor too.  In the end I had about 20 hours getting it out and torn down.  Dropped the block, head and piston combo off at the machine shop.  Crank is fine, block has a slight ridge and a wavy surface on the bore from the rings failing.  Check the picture, #3 and #6 piston (low comp 1mm in the bore at TDC) had the ring lands blown out.  Head gasket was failing number 3, 5 and 6 rust streaks from water seaping in the chamber by the gasket.

The cam fiasco is aggrevating, but then we didn't realise what was under the valve cover before he ordered parts.  Why MB would change the cam tower bores by 1mm is beyond me...

Please keep the comments and help coming.  I'll reply back with more as I get info from the machine shop.

Jamie

Cirrently rebuilding a '71 SL

[ja17]

Hello 71280-SL,

The result of my search.... The pistons you mention 130 030 0117 are Mahle #176-02, three ring, 87.5 mm bore and are meant to give you 9:1 compression! They are flat topped.
The pistons you need to give you the original 9.5:1 compression are Mercedes #130 030 9717 Mahle #175-02. these are "stepped" pistons a newer design than original, but do give you the correct high compression. These are also a three ring piston.
This information is from some fairly old catalogs of mine so I have no idea if these part numbers are still current.

The original 9.5:1 engines were designed to run on 95 octane or above fuels. Don't make to big a deal over the 7 lbs of compression you would be giving up with the other pistons. Any advantages gained with the high compression would probably be off set by the loss of power from retarded ignition timing from 93 octane fuel.
 More to come!



Joe Alexander
Blacklick, Ohio

[ja17]

Hello and welcome MD Rebuilder,

Yes it can be confusing. It seems that the factory never stops re-designing and improving the original design. Often times these subtle changes come with a long list of additional parts required to perform the upgrade!

Concerning the camshafts, depending on how many parts you wish to change any of these cams will work on these engines. Naturally most people upgrade to the improved, newly designed  versions in most cases.

A brief camshaft history for the W113 engine; the earliest camshafts had internal oil bores like the crankshaft for oiling. The cam bearings were of a smaller diameter, the rocker arms and cam lobes had smaller rubbing surfaces and the ball stud adjusters bolts were 14mm instead of the later 17mm. Sometimes the foot of the camtowers was thicker or thinner causing the head bolts to be different lengths in some models.

Mercedes decided that a solid camshaft would be stronger so later camshafts were solid and an external oiler tube was added to the newly designed camtowers (cam bearings). The next major change came a year or two into the 280 series when Mercedes re-designed the camshaft to have wider lobes and rubbing surfaces on the rocker arms. The valve adjuster "ball studs" were changed and now had a 17mm valve adjustment bolt. This seemed fine for a while until they decided the cam should have a 1 mm larger diameter on the main bearing journals (around 1969). This change required the replacement of the camtowers with the newly designed camshaft.
In addition to all these significant changes, during this period the factory occasionally would improve camshaft timing,  material or construction of these new camshafts which entered the mix with their own ID numbers.
In general the 280-SL specific camshafts and 230-SL camshafts are the most radical.
The #08 camshaft you mention is even less desirable than the mediocre #05 in terms of power.

Joe Alexander
Blacklick, Ohio

[n/a]

Joe, pretty good info, I appreciate the effort to type it all in.  I'm probally going to shake my fist in rage at the cam issues.  You stated about newer cams that fit the towers.  Is there an aftermarket for these designs.  I almost wonder if I could send the buggered 05 cam I have to Crane Cams and get them to wittle one out of billet steel with better timing and lift curves.  Seems like it would eliminate these problems and probally cost less than the 08 cam and nused cam stands.  It would also be nice to put a roller follower setup in.  That's the engineer part of me coming out.

The parts expense is going to hurt very much.  For $175 for a fan clutch I'm going to scour the junk yards for a sutable replacement and go that route.  The goal for the car is to look stock, but run much better than a stocker while keeping the mechanical FI setup.

Cirrently rebuilding a '71 SL

[hands_aus]

Hey MD Rebuilder,

The fan clutch is available aftermarket.
The one I bought was made by Behr (one of MBs parts suppliers) and at half the MB price. It was sold to me by the MB workshop.

You are better off using an aftermarket unit rather than a second hand unit.

Bob (Brisbane,Australia)
early 250 SL, RHD

[n/a]

to: Dan Caron and Joe Alexander ...have received letter from Mahle Piston Co...they state that the correct piston which is really all that is available is their #001 76 02  which equates to the OE ref. 130.030.91.17, this piston is their 2nd oversize (1mm) which increases engine to 2823cc, since I now have months of research on this product I find no mention outside of someones post on this board that the piston correctly installed will stick out of the block by l/2 thickness of cyl head gasket which is .080, can you hands on people confirm this? although I have mechanic and race oriented machine shop which will probably cc the cyl head and machine top of block to get us in the right area. Of prime importance here is the valve to piston clearance...Again I am shooting for a finished compression of 9.8-1  thanx all.

[Benz Dr.]

What you want to do is go by the maximum amount the pistons can protrude out of the block then subtract the minimum valve to piston clearance from that. So with the head installed you need .9mm clearance between the intake valve and piston at 5 degrees ADTC.
If you have 2mm clearance right now and the head has .5 mm material left before it's a door stop you need to subtract that from the total amount. This will give you .6mm clearance when the cylinder head is machined down to 84mm minimum thickness. You should keep in mind that things happen and never go below any minimums at any time.
Since I not only had to machine my cylinder head but also the block I think a safe margine on the block would be at least .5mm with maximum piston protrusion.
In other words, you should still have .5mm of material that can be removed from the top of the block before the pistons are at maximum protrusion. Removal of this .5mm would leave a margine of only .1mm between the valve and piston with a minimum thickness head. This would be safe for operation but would leave you with nothing should the block ever be damaged.

Dan c

Daniel G Caron

[Shvegel]

Hi,
  Didn't have time to read all the posts so if this is covered please ignore this post.
  All things being equal if the oversize pistons were installed at the same height as stock pistons the compression would actually be higher than the stock bore piston due to the increased area of the piston. maybe they are actually shorter in the pin bore to crown height for that reason.

[Benz Dr.]

Maybe I'm wrong but I think that increasing piston size will only increase total CC's and not compression ratio. All things being equal compression ratio should stay roughly the same. When you decrease the cumbustion chamber size by milling the head or block this will increase compession ratio. When the 250 SL block was created all they did was increase the piston travel
and it only increased by .2 compression ratio.

Dan c

Daniel G Caron

[Shvegel]

More air being stuffed into the same space will raise compression just as decreasing the size of the combustion chamber by milling the head.
 I don't have time right now to do the math(just bought a house and am in spackle hell) but a 1mm increase in bore x the stroke is a subtantial amount of additional space that is compressed into a similar combustion chamber. A quick spatial calculation leads me to believe you would need about a 3mm drop in compression height to equal the same compression ratio.