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  #1  
Old 04-29-2011, 04:59 PM
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Cleaning the block/cylinders for new head

Finally got the head back for the '79 300SD and going to install it this weekend. Any thoughts to offer this rookie as to the "proper" way to prep the work area? Specifically have stuff on the block surface that would come off really well with a green scrubby or a wire brush and some Marvel Mystery Oil. Want to get it "hospital clean" before laying the new head gasket down. Also, there appears to be some hardened material on the upper cylinder ring sleeves that would be great to clean up also.

Thanks!

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  #2  
Old 04-29-2011, 08:38 PM
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A flat razor and appropriate holder will be your most valuable tool. Buy at least 20 of them. Keep the razor at a shallow angle and flip it over often. Replace just as often.

Some like the green scrubby, I have used it when the pistons are out or as a last resort on a stuborn stain when pistons are in. But it is not ideal... neither is any abrasive that will leave remnants behind.


The razor is also great for the carbon buildup at the tops of the sleeves. However, there is no reason to remove carbon from the inner cylinder when doing a head job. Just remove the carbon from the head surface and all headgasket remnants.
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  #3  
Old 04-29-2011, 08:47 PM
Gene
 
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Sir, do not use a Scotch brite pad ANYWHERE NEAR THE EXPOSED CYLINDERS! It leaves behind abrasive. It'll RUIN things.

I used a gasket scraper, and a vacuum to ensure I sucked all the debris out of the cylinders, even after stuffing them with rags. We used to use a stone to "stone" the deck as well. I wouldnt muck with the carbon at the cyl tops unless it's severe.

This is "cleanroom" time.
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  #4  
Old 04-29-2011, 09:42 PM
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I prefer a twisted wire cup on a side grinder. a little spray of gasket remover works wonders. (don't use the wire wheel with the spray on the block!!!!)
with the razor blades, to remove the residue from the spray.
then clean up well with brake cleaner, and use the cup on the grinder to get it hospital clean. more brake spray, and a tad of compressed air.
wipe with lint free rags. totally stuff all the pots with rags first!
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  #5  
Old 04-29-2011, 10:27 PM
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Thanks for the insight. I had read somewhere to blow out the bolt holes to get the junk out of them as well. Is the risk that minute particles of whatever can slip past the rings? Also, am I shooting for a completely silver surface on the block or just getting it so it's smooth, but a stain or two is left behind.

Not to be a total neophyte but what happens if some minute particles of crap get down inside the pistons during this process? My plan is to change the oil at least twice after putting it all back together, once virtually right away (minutes) and another after a very short timespan (hours). Or is all it takes is one speck of _________ and you're hosed?

Much like a great paint job, I know it's all in the prep and want to do it right.

Lastly, in the FSM it makes no mention at all of any type of adhesive for the gasket. Just lay it down and tighten (slowly) in sequence?

Thanks again. Really much appreciated!
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  #6  
Old 04-29-2011, 10:34 PM
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blow the holes out with compressed air, keep a rag around the hole while you blow it out to catch oil etc.

In a perfect world, the machine shop would skim the block for you. But here, the best you can do is bare metal.. it will do more damage to try to remove ALL the staining. One good indicator that a stain is benign is to use the angle of light to judge the surface in that region and compare it with the texture on the stain. As long as the surface texture is maintained throughout, you have done what you can.
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Old 04-29-2011, 10:38 PM
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getting junk in the cylinders is not cool.... but its gunna happen.

Thats why you want to keep them dry and make sure the only material that can fall in there is carbon and gasket bits. Using a flat blade reduces the chance of putting foreign material into the cylinders that could be potentially harmful to the pistons, rings etc..


no adhesive... some like to use a copper spray... but its silly for an iron head. Just clean the block when you are done with spirits, or xylene... brake cleaner.. .whatever leaves the least residue that you like to use.
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Old 04-29-2011, 10:41 PM
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lets say a few strands of steel wool fell in a cylinder.... you are not going to lose compression on that bore to any noticeable degree.

but if you used a bunch of sandpaper on the entire surface... you get the idea.
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  #9  
Old 04-29-2011, 10:41 PM
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Thanks JT. This project started out as just R&R the head gasket on a really nice 300SD that otherwise was in really good nick and I got for a song because the PO didn't want to deal with it. Once I got the head off, the "while I'm in there I might as well..." took over and I ended up sending the head out to be totally redone, prechambers, everything. Then figured I'd rebuild the turbo. Figured since the turbo was off and the starter was right there...might as well get the starter rebuilt. New water pump. Rebuilt the vacuum pump. Blah blah blah. It is a labor of love on these W116s though. Really do respect this and want to do it right.
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  #10  
Old 04-29-2011, 10:44 PM
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its very true.

You won't regret a thing. The first one I did, I slapped my old head back on after a visual inspection and a few wiggles of the valves thinking it was 'good enough'... bad move. I just had the head rebuilt properly a few months ago.

Do it right ONCE!

Hope you plan on posting pictures (especially that rebuilt turbo.)
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Old 04-29-2011, 10:47 PM
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If you have the engine on a stand, turn it over and blow the cylinders out. Then I pour a little oil around the pistons in the bores, turn it over by hand once, wipe, turn over, wipe. The oil will tend to stick contaminants to the cylinder walls where you can wipe it off.
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  #12  
Old 04-29-2011, 10:49 PM
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Phil helped me quite a bit sourcing parts for the vacuum pump rebuild and other bits I got off the site here. On the turbo I ended up getting the ************** kit. Pretty straight forward. I had the shop that did my head balance the turbo also after I rebuilt it. Figured, got that far why cheap out. It was only $40 to have them do it. I did take some pics. I'll post em up.
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1975 450SL
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  #13  
Old 04-29-2011, 10:52 PM
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Still in the car Jeff. I left it at TDC and don't want to mess with anything if I can avoid it! But if it comes to dropping the oil pan and doing that, I guess WTF. Not looking for more work though! Roy lives about 20 mins from me. If I become the cowardly lion I'll ring him and raise the white flag! But I'd rather do it myself. Pride you know.
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1975 450SL
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  #14  
Old 04-29-2011, 11:41 PM
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Blowing out the holes with compressed air is not good enough ...by a long shot...

You need to get two taps for those holes.... proper size of course...one regular and one bottoming ... used last..... then put heavy grease on the tap.. or you can also put a stick of candle wax into the hole and then run the tap in.. this will both clean the threads... very important for getting proper torque readings on the head bolts.. and take all the junk out of the hole.. I think there may be an advantage to using a ' gun or spiral flute ' tap ... or they make one which does a better job of expelling the wax... this is much faster than the perfectly acceptable way of using heavy grease to catch the junk and bring it back out through multiple insertions... cleaning it carefully between each procedure....
... What is that saying ..." pride goeth before the fall " ?
If you have any doubts go to Roy....you have a LOT invested in many ways... no time to mess up at the very last..
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  #15  
Old 04-30-2011, 12:50 AM
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Its true, you need to clean the threads well... but a tap is not necessary unless you have some seriously rusted bolts that come out.

The chances of finding a tap that perfectly matches the threads are small.... too many manufacturers. You will end up cutting metal in each hole, making a mess and weakening the threads.

All you need is a bolt, some brake cleaner / xylene and rags. Shine a light into the bore: no gunk at the bottom?... done. Have gunk?.... keep cleaning. (pipe cleaners?)

Then use a clean bolt with no imperfections to chase the threads. Grind off one or two sides of the bolts threads to catch dirt like a tap would.

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