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M127 engine valve problem

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Bambo Jr.'s picture
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My 63 220SEb M127.984 134 hp engine burnt a valve in a strange way (see picture). Instead of the seating area of the valve, there is a pinhole in the tulip area. Did this model come with sodium filled valves? What could have caused a pinhole like that? It was discovered when I made a compression check and the result in the #5 was 60psi! I squirted oil in the cylinder and another check brought the compression back to normal giving me the impression that I had a broken or stuck compression ring when in fact the oil was temporarily filling the pinhole! Removing the head was a relief upon discovering the valve as opposed to a possible broken ring and scored cylinder and possible engine replacement. Appreciate any comments for cause.

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ja17's picture
Blacklick, OH
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2002 SLK32 AMG Kompressor
1990 300TE
1988 190E
1986 560SEC
1983 300TD
1974 450SLC

Hello Greg,
The exhaust valves on the M127 engine are sodium filled. The area burned on your valve is not that unusual. The pinhole, was close enough to the edge where leakage was occuring. Burnt valves are usually caused by an extremely lean mixture or leakage of hot gases past the valve. This leakage can be a result of wear, too tight of a valve adjustment, mechanical damage or possibly carbon built up under the valve seat. Wear is the most likely cause, especially if the engine has a lot of miles on it and the head has never been recondtioned. The valve guides and/or the valve stems will wear causing the valve to eventually wear it's face or seat until it leaks hot combustion gases and burns. I believe this engine had the valve rotators under the valve springs. Make sure these are all working properly.
You are probably in for the proverbial head reconditioning. The vaves, valve seats, and valve guides will be checked and replaced or reconditioned. New valve seals will vbe installed. If your timing chain has 100,000 miles on it replace it at this time also. If the head is warped more than allowable, it should be milled or straightened . Only mill if necessary since the head will be scrap if it is milled too much. Find a good experienced machine shop to do the work or you will be wasting a lot of time and money. Keep us posted.

Joe Alexander

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Joe Alexander
Blacklick, Ohio

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JOE,
Thanks for the detailed advise. I checked and this engine doesn't have valve rotators. We are replacing all the exhaust valves as the valve seating surface doesn't allow much room for grinding. Did MBZ design them this way to reduce weight? We are installing silicone bronze valve guides and new seals and will also replace the timing chain as you mentioned. Sending it to a reputable machine shop to have the valve seats ground and from the looks of the head it doesn't appear to have any warping. I will post again when we get the engine put back together. Thanks, Gregg

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2002 SLK32 AMG Kompressor
1990 300TE
1988 190E
1986 560SEC
1983 300TD
1974 450SLC

Hello Greg,
WOW, it looks like you have spent a lot of time under that hood. Did you get your hands dirty at all getting the head off! Nice condition finbacks are so hard to find now days. The 220-SE was one of the best sedans ever made. I once owned a very nice four speed stick, sunroof 220-SE sedan.
Considering the massiveness of the cast aluminum intake manifold, I don't believe weight was a major consideration in engine design. You usually can grind the valves and seats once or twice before replacement is needed, depending on the damage. Yes the earliest versions of this head did not have the valve rotaters. If you need any factory specs the Mercedes Technical Data Booklets or shop manuals ,should help. If you do not have the specs e-mail me. It would be nice to see a photo of the entire car at some point. Good luck.

Joe Alexander

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Joe Alexander
Blacklick, Ohio

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Joe,

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Joe, Pressed the wrong key. Thanks for the reply and info. What I was referring to with regard to the weight was not the weight of the engine but the possiblity of designing the valves with minimum material and weight to lighten up the valve train for better response and possible hp gain. This M127 engine is way underpowered for the mass of automobile it is required to motivate. While I have the head off, I considered taking the cam over to a local cam grinder for a profile change. Knowlegeable MBZ people informed me that it wouldn't be a good idea with this engine. Maybe sometime in the future, if I can find a complete M130.983 185HP engine and later transmission, there will be a swap. Since I'll keep this car forever, keeping it original is not a priority. I've already transferred the battery from the engine compartment to the trunk, converted from a generator to a 63 amp internal regulated alternator, converted the radiator to a modern hi-efficiency 3 row core, installed a coolant recovery tank, replaced the ignition points with a Pertronix module, replaced the original wheel with a Nardi wood steering wheel, replaced the radio with a Becker Mexicao AM/FM/tape stereo with additional speakers and of course polished the valve cover. Attached is a picture as requested. Gregg

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Nice 220SE Cabrio !! Still has 13" wheels. Looks great. I hope you're using MB valves and valve seals on this repair. This car deserves the best.

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Tom Hanson
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Mercedes-Benz Classic Center USA
MBUSA, LLC
thomas.hanson@mbusa.com
949 598-4842 direct.

Prior MB cars: 2010 ML350 Bluetec, 2003 C320 Coupe, 1986 300SDL, 1971 300SEL 6.3, 1973 450SE, 1959 220S, 2011 C300

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1990 300TE
1988 190E
1986 560SEC
1983 300TD
1974 450SLC

Hello Greg,
I should have known, a very nice cab, in euro trim.
Regrinding the camshaft can create problems. If the camshaft is not hardened afterward, (as original) it probably will not last. A stock 230-SL camshaft is much hotter and would switch out easily. Yes changing over to the later M130 engine (as used in the same chasis 280 series) would be a fairly easy swap. Find a nice 280-SE donor sedan.
Be sure to use an original new head gasket. New "old stock" head gaskets will not have the latest improvements in materials and design.

Joe Alexander

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Joe Alexander
Blacklick, Ohio

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A 250SE engine would go nicely in there as well.

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Tom Hanson
Supervisor, Parts Operations
Mercedes-Benz Classic Center USA
MBUSA, LLC
thomas.hanson@mbusa.com
949 598-4842 direct.

Prior MB cars: 2010 ML350 Bluetec, 2003 C320 Coupe, 1986 300SDL, 1971 300SEL 6.3, 1973 450SE, 1959 220S, 2011 C300

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Valve job complete

Finally got the head back on, completing the valve overhaul. The job was an interesting discovery in that this engine had been rebored and the valves having been ground prior to my possession. That is why there were no ridge lines in the cylinder bore and explained the thinness of the valves. Ended up replacing both exhaust and intake valves (not cheap), installing silicone bronze valve guides with seals and replacing the timing chain. Machine shop said the head was slightly warped and therefore shaved it, which required shimming one of the camshaft towers. I'm assuming I might get a small increase in compression value. Can't believe the difference in smoothness, pep and acceleration that I now have! Amazing what a pinhoe in one cylinders defective valve can do to performance. Since access was so easy with the manifold off, I also changed the motor mounts which was fortuitous because the right one was bad. Boy it feels good when your car is purring!

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2002 SLK32 AMG Kompressor
1990 300TE
1988 190E
1986 560SEC
1983 300TD
1974 450SLC

Hello Greg,
Great that you are back in action already! You will probably see a bit more increase in compression on the front and rear cylinders, since shaving the head removes most material material from the front and rear of the head. Of coarse the compression in the bad cyllinder will be much better. The improved material, silicone bronze guides should last longer than the originals.
It is recomended that you re-torque the cylinder head hot after first warm-up and again at around 500 miles. An oil change during or after the valve job is good also. Any dirt or contamination from the work will be drained off with the oil.

Joe Alexander

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Joe Alexander
Blacklick, Ohio

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HUH?

"Shaving" (sic) the head had better not "remove most material from the front and rear of the head".If my machinist did that,he'd be buying a new head for me.
Can I watch while you change the oil "during the valve job"?.

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2002 SLK32 AMG Kompressor
1990 300TE
1988 190E
1986 560SEC
1983 300TD
1974 450SLC

Hello Steve,
Think about it. When the head warps it arches in the center. Cutting it flat again removes material from the ends (cylinders one and six mostly). I am not talking major amounts, just thousanths of an inch. Some shops today attempt to straighten the heads first prior to shaving or milling them so less material is removed.
The oil can be easily changed while the cylinder head is off and being re-conditioned or as soon as it is installed.

Joe Alexander

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Joe Alexander
Blacklick, Ohio

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