220s ( 1959) inlet valve clearance

1953-1961: 180, 180a, 180b, 180c, 180D, 180Db, 190, 190b, 190D, 190Db, 220a, 220S, 220S cabrio., 220S coupe 220SE, 220SE coupe, 220SE cabrio.
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efirestorer
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220s ( 1959) inlet valve clearance

Post by efirestorer » Tue 23 Jul, 2013 1:15 pm

Question for technical gurus , have just had head refurbished by reconditioner , and noticed in workshop manual ( for 220S ) reference to " permissible depth of valve disc in relation to cylinder head separating surface ". Measuring mine ( having had a skim on head face down to height of 84.8 mm ) the worst clearance is .63 mm , manual says .8mm. Do I take it back to have seats machined / let in further - to get the .8 clearance or can I use the specification shown in 220Sb manual where a minimum distance between inlet valve and piston with the crankshaft adjusted to 5 degrees after TDC is .9 mm?. If using the finny method , what is a reasonable figure to use for the head gasket thickness?.

efirestorer
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Re: 220s ( 1959) inlet valve clearance

Post by efirestorer » Fri 09 Aug, 2013 12:49 pm

All sorted - A. reconditioner readily agreed that he should have checked clearances and he reworked the valves to get the specified .8 mm clearance.
B. I also checked when all reassembled and with inlet just opening and 5 degrees ATDC had at least 1mm clearance between piston and valve.
C. reconditioner also suggested could probably have got away with the close clearance but to be safe , best to correct it.

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Mercmad
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Re: 220s ( 1959) inlet valve clearance

Post by Mercmad » Sat 10 Aug, 2013 1:35 pm

Yep,when the engine is run in andf you are pulling full revs,the valves can nick the pistons. Just goes to show how precise these guys were in the 50's .In fact i am rebuilding a 1937 170V engine for a customer and the factory manual calls for the same degree of acuracy....on a sidevalve engine!!
:laughing6: :laughing6:

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Greg in Oz
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Re: 220s ( 1959) inlet valve clearance

Post by Greg in Oz » Mon 12 Aug, 2013 12:19 am

If pistons and valves touch each other in a sidevalve engine, things have gone horribly wrong! :think: :Doh:
107023 - 350SLC: 1973, 3sp auto, icon gold, parchment MBtex (sold July 2012 after 29 years ownership)
107026 - 500SLC: 1981, 4sp auto, thistle green, green velour
124090 - 300TE: 1990, 4sp auto, arctic white, cream-beige MBtex
124090 - 300TE: 1992, 4sp auto, malachite (spruce green), black MBtex
201024 - 190E-2.0: 1985, 5sp manual, black, black MBtex
201028 - 190E-2.3 Sportline: 1990, 5sp manual, arctic white, blue leather
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Mercmad
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Re: 220s ( 1959) inlet valve clearance

Post by Mercmad » Mon 12 Aug, 2013 8:17 am

ImageI posted this before Greg,when a Sidevalve piston meets a valve it is indeed an ugly sight... :laughing5: :laughing5: :laughing5: .I meant the overall dimensions and assebly of this baby mercedes engine requires a lot of effort to meet the factory specs. It should perform well though. The original engine was full of silicone sealer to prevent water leaks... and Mazda pistons which stopped 10mm below the deck height. talk about low compression!!. The inside of the head was full of the silicone so water wasn't circulating anyway.
:smurf: :smurf:

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Cyril Perrier
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Re: 220s ( 1959) inlet valve clearance

Post by Cyril Perrier » Fri 20 Jun, 2014 1:17 am

Good day efirestorer
I have just read your post with much interest. I am also the owner of a 1959 220S Ponton and I am having the same issue you had 5 years ago. In brief I had my cylinder head skimmed and the reconditioner did not do anything to the valve clearance to compensate for the height lost, as indicated in the manual. Now the cylinder head has been put back on the engine but cylinders 1 and 2 are fouling their plugs with carbon. I tried interchanging their plugs with those of two other cylinders that burn ok but cylinders 1&2 still fouled the new plugs. I don't know if this could be due to the fact that the depth of the valve seats have been reduced. Do you by any chance remember what were the symptoms your car had before the reconditioner reworked the valves? Or can anybody advise on this? What symptoms should I expect with the valves as they are currently. Thanks in advance for any advice.

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Cyril Perrier
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Re: 220s ( 1959) inlet valve clearance

Post by Cyril Perrier » Fri 20 Jun, 2014 2:22 am

In reference to my above post: I forgot to say that I did a compression test of the cylinders. The two that are fouling their plugs have the highest compression of the 6. They read 175 and 160.

efirestorer
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Re: 220s ( 1959) inlet valve clearance

Post by efirestorer » Fri 20 Jun, 2014 9:17 pm

Cyril , My car was running fine before skim - head had to come off for a stripped thread in rocker post attachment and was skimmed to ensure a perfect surface for the head gasket. I did not reassemble after the head skim until the clearance issue was sorted. Sorry can't help with your problem.

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Cyril Perrier
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Re: 220s ( 1959) inlet valve clearance

Post by Cyril Perrier » Sat 21 Jun, 2014 1:01 am

Thanks for your prompt response 'efirestorer'. Anybody else can help on this issue? Thanks in advance.

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Mercmad
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Re: 220s ( 1959) inlet valve clearance

Post by Mercmad » Wed 02 Jul, 2014 8:38 pm

Cyril Perrier wrote:Good day efirestorer
I have just read your post with much interest. I am also the owner of a 1959 220S Ponton and I am having the same issue you had 5 years ago. In brief I had my cylinder head skimmed and the reconditioner did not do anything to the valve clearance to compensate for the height lost, as indicated in the manual. Now the cylinder head has been put back on the engine but cylinders 1 and 2 are fouling their plugs with carbon. I tried interchanging their plugs with those of two other cylinders that burn ok but cylinders 1&2 still fouled the new plugs. I don't know if this could be due to the fact that the depth of the valve seats have been reduced. Do you by any chance remember what were the symptoms your car had before the reconditioner reworked the valves? Or can anybody advise on this? What symptoms should I expect with the valves as they are currently. Thanks in advance for any advice.
Plug fouling has nothing to do with valves, I would say that in fact that the rings were worn and now that you have better valve sealing ,oil is being sucked up into the combustion chamber. Also, if the head was only skimmed,but nothing done to the valve guides or seals you will get oil leaking down into the combustion chamber under deceleration as vacuum is increased.
If it is fuel fouling (really black dry fouling) I would suspect the front carb being out of adjustment or not synchronised with the rear carb. Oil fouling is wet and very black. Another cause of fouling on a Mercedes engine is the use of resistor plugs and carbon string leads. Use only the copper core leads and NGK BPR6 ES plugs. if you want to prevent fouling from oil, use BPR 5 ES plugs.
Pontons run far better if you get rid of the points and condensor and go to a pertronix ignitor set up.

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