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560SL 1986 244k miles astral grey / black
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Emotional reason vs economical reason, both are probably correct, but do what feels best for you Jyuma!

Ps if Mahle is giving you trouble with sending a piston to the states, let me know, they might be more flexible sending it within Europe first and I’ll send across the pond.
 

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1983 380 SL
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2,506 Posts
Discussion Starter #162
Emotional reason vs economical reason, both are probably correct, but do what feels best for you Jyuma!

Ps if Mahle is giving you trouble with sending a piston to the states, let me know, they might be more flexible sending it within Europe first and I’ll send across the pond.
Thank you for the offer. I'm still waiting to hear from Mahle. You all will be the first to know when I do.
 

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1983 380 SL
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2,506 Posts
Discussion Starter #164
J, you inspire us all. I sure hope there's no more ticking when you're done.
Thank you for your kind words but don't encourage me, there are some who think I've already gone too far with this engine and they're probably right. :unsure: :unsure: :unsure:
 

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1999 SLK55 AMG + 6 speed swap, 2001 CLK55 AMG - parts
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74 Posts
So just a few things from personal experience:

1. I have seen light hones/bores done without the re-application of the silicone coating with zero effects. At the end of the day, your oil is doing most of the lubricating on that surface
2. I have also DIY honed cylinders that had gouges much like yours, got new pistons and rings and rebuilt with zero noticeable effects. As long as you are not re-gouging the piston, there is no harm done. Is there a chance of blow-by? of course! but it is minimal and, again, I witnessed no long term ill effects.
3. have you considered Tig welding the gouges and then boring to original diameter? I've seen that done too. I'm not sure how it would react with the Alusil though. (if the block is actually saturated with it)

Just a few thoughts! I'm enjoying the project and I think you are doing all the right things!
 

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1983 380 SL
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2,506 Posts
Discussion Starter #166
So just a few things from personal experience:

1. I have seen light hones/bores done without the re-application of the silicone coating with zero effects. At the end of the day, your oil is doing most of the lubricating on that surface
2. I have also DIY honed cylinders that had gouges much like yours, got new pistons and rings and rebuilt with zero noticeable effects. As long as you are not re-gouging the piston, there is no harm done. Is there a chance of blow-by? of course! but it is minimal and, again, I witnessed no long term ill effects.
3. have you considered Tig welding the gouges and then boring to original diameter? I've seen that done too. I'm not sure how it would react with the Alusil though. (if the block is actually saturated with it)

Just a few thoughts! I'm enjoying the project and I think you are doing all the right things!
Thanks for your response. I have learned much about my Mercedes block along the way but perhaps the most surprising thing I learned is that there is no "coating" on the cylinder walls of an ALUSIL block. That's one of those urban myths.

An ALUSIL block is cast with a mixture of molten aluminum with particles of hard silicon mixed in. The silicon is found throughout the entire casting of the cylinders. The cylinders are then honed using standard honing technique and brought to final spec via ever finer honing stones. Once the cylinder is honed to spec, the honing stones are removed and replaced by stiff felt pads.

The cylinders are then coated with a honing paste called AN-30 which contains among other things... silicon particles. The cylinders are then honed for a specific amount of time, usually no more than 90 seconds, using this honing paste who's function it is to wear away the aluminum from between the hard silicon particles cast into the cylinder walls.

The final hone with AN-30 does not increase the diameter of the bore... it just removes microscopic amounts of aluminum from between the hard silicon particles. These microscopic holes help retain oil in the cylinder walls as the rings glide over the hard silicon particles without contacting the aluminum between the silicon particles.

That's how an ALUSIL system works. It is imperative that the coating of AN-30 be completely cleaned off the cylinder walls before reassembly as the silicon in the paste would be destructive to the cylinder walls and just about everything else in the engine. Meticulous care must be taken to remove every trace of the AN-30 paste.

I already honed the #6 cylinder with AN-30 paste and it did nothing other than produce a matt finish which is exactly what it is supposed to do.

Sorry for the long winded explanation but I thought it might be as interesting to others as it was to me. :)
 

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1983 380 SL
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2,506 Posts
Discussion Starter #167
I just heard back from Mahle. They were very sorry but they stopped making the piston I need 7 years ago. They suggested I try the aftermarket. Unfortunately I have not been able to locate any 1st or 2nd repair pistons for the 380. Looks like the decision has been made for me. Insert the sleeve and bore it to a category 1 or 1+, these are the only pistons I have.
 

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1987 560 SL, 1990 300E 4Matic
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473 Posts
A long shot for sure, but this ad has been up on the MB club of America classifieds. He could happen to have a NOS piston on hand.

Also, I just came across these "0" stamped pistons on ebay. Looks like $75 ea.

 

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1983 380 SL
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2,506 Posts
Discussion Starter #169
A long shot for sure, but this ad has been up on the MB club of America classifieds. He could happen to have a NOS piston on hand.

Also, I just came across these "0" stamped pistons on ebay. Looks like $75 ea.

Yeah, I saw those but they're even smaller in diameter than the ones I already purchased. My block is marked 2 as are my original pistons (88.010) they're one hundredth of a mm over the standard 88.000 which is .00039 inches (3.9 tenths) which is extremely tiny but it must mean something if MB went out of it's way the categorize the pistons as 0, 0+ 1, 1+, 2, 2+.

My path has been pretty much determined for me... sleeve #6 and bore it to spec for a 1+ piston. It will cost me $400 bucks but I'll live with that if it solves my problem. And with a nod to @AlterSchinken I'll go with new rings... why not?
 

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1983 380 SL
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Discussion Starter #170
I'm looking into buying new rings but I can't make any sense out of the size requirements. My pistons are all stamped with a 2 and 88.010.

88.010 is 3.9 tenths over standard... that's .00039 inches. I can't even measure that on my caliper. The smallest increment my caliper can measure is .0005 (5 tenths) and when I can get my caliper to read 5 tenths I can't see any daylight between the jaws of the caliper... minute dust particles alone take up more room.

When replacing rings you're supposed to place the ring inside the cylinder and measure the gap. Proper procedure calls for filing the ring ends to adjust the gap. Huh? I can't measure tenths! Am I spinning my wheels over nothing? Does it really matter that my pistons are 88 mm + .00039 inches rather than 88.000 mm +0000 inches?

What should I be ordering... and while we're at it... Autohausaz has rings for under $30 per set but I've seen rings for my engine going for over $80 per set. Is Autohausaz selling shit rings or are they cast versus chrome? What should I be buying and where should I be buying them?

Thanks
 

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1985 380 SL
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88 Posts
I'm looking into buying new rings but I can't make any sense out of the size requirements. My pistons are all stamped with a 2 and 88.010.

88.010 is 3.9 tenths over standard... that's .00039 inches. I can't even measure that on my caliper. The smallest increment my caliper can measure is .0005 (5 tenths) and when I can get my caliper to read 5 tenths I can't see any daylight between the jaws of the caliper... minute dust particles alone take up more room.

When replacing rings you're supposed to place the ring inside the cylinder and measure the gap. Proper procedure calls for filing the ring ends to adjust the gap. Huh? I can't measure tenths! Am I spinning my wheels over nothing? Does it really matter that my pistons are 88 mm + .00039 inches rather than 88.000 mm +0000 inches?

What should I be ordering... and while we're at it... Autohausaz has rings for under $30 per set but I've seen rings for my engine going for over $80 per set. Is Autohausaz selling shit rings or are they cast versus chrome? What should I be buying and where should I be buying them?

Thanks
Since you are not "reconditioning" the other 7 cylinders the select fit classes really don't matter. If you are able to lightly fine hone and lap with the compound the bores will be even bigger. The rings are the same for all of the different classes. The select fit process is mostly about controlling noise. Since the bores with wear will be bigger than original you shouldn't have a problem with ring gaps being too small, but they should be checked to account for manufacturing tolerances. The gaps will likely be out of spec on the big side in any case. I see the cheapest rings are made by Schoettle (never heard of them) but they are sold by FCP Euro which is a good supplier. Then there is Goetze, a division of Federal Mogul and manufactured in Germany.
 

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1983 380 SL
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2,506 Posts
Discussion Starter #172
Since you are not "reconditioning" the other 7 cylinders the select fit classes really don't matter. If you are able to lightly fine hone and lap with the compound the bores will be even bigger. The rings are the same for all of the different classes. The select fit process is mostly about controlling noise. Since the bores with wear will be bigger than original you shouldn't have a problem with ring gaps being too small, but they should be checked to account for manufacturing tolerances. The gaps will likely be out of spec on the big side in any case. I see the cheapest rings are made by Schoettle (never heard of them) but they are sold by FCP Euro which is a good supplier. Then there is Goetze, a division of Federal Mogul and manufactured in Germany.
Thanks. What about the rings being sold by Autohausaz? Any good? Shouldn't I be using Chrome rings?
 

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1983 380 SL
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2,506 Posts
Discussion Starter #173
I stopped by the machine shop today to visit my block and talk to the owner. We discussed what to do and we mutually decided on boring the cylinder for a sleeve and then honing the sleeve to fit the 1+ piston I brought with me. We had a good laugh over the tolerances… well, I laughed he just smiled and said we routinely hold tolerances to tenths.
I asked how long and he estimated 2 weeks... so I'll order the bearings, rings and gaskets and just keep cleaning parts until the block is done. Once I get the block back I'll tackle TimeSert'ing the head bolt threads and begin reassembly.
 

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1987 560 SL, 1990 300E 4Matic
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Since you're going to sleeve your cylinder, would one of the "0" ebay pistons be an option (less, if any boring of the sleeve needed than for a +1 piston) or would matching the other +1 pistons be the better option in terms uniformity?
 

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1983 380 SL
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Discussion Starter #175
Since you're going to sleeve your cylinder, would one of the "0" ebay pistons be an option (less, if any boring of the sleeve needed than for a +1 piston) or would matching the other +1 pistons be the better option in terms uniformity?
A category 1 piston measures 87.995 mm and a category 1+ is 88.000 mm a difference of .005 mm which in decimal is less than 2 tenths. Five tenths is 1/2 of 1000th of an inch. So the difference between a category 1 piston and a category 1+ piston is about 2 ten thousands of an inch. By those factors it really doesn't matter if I use a category 0 or 1 or 2, the difference is minute. The only consideration will be how much honing the machine shop will do after the sleeve is inserted and rough bored to the initial dimension.

I already bought 4 used pistons on eBay. That's where I got the 2 category 1 pistons and the 2 category 1+ pistons. The machine shop is going to use an .090 sleeve (I believe the actual dimension is .093). The 2nd repair size is +1 mm which is .039 inches so he'll bore the cylinder by something just over 2 x's the 2nd repair size ( .093) and then hone the sleeve to fit the 1+ piston exactly + tolerance in tenths). It should work out fine. The thickness of the cylinder walls is just shy of 1/2" (.500) so after boring, the thickness of the cylinder wall (not counting the sleeve) will be right around .400. Again, it s/b OK. If this were a high compression high rpm high power engine I'd worry about a cylinder wall of only .400 inches thick, but the low power 380 should tolerate that wall thickness without any trouble.

The saga continues. :)
 

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'85 300tdt (sold),'64 220b,'63 220Sb ,85 monte carlo ss 406SBC(4 sale),1976 vega wagon(sold)
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So just a few things from personal experience:

1. I have seen light hones/bores done without the re-application of the silicone coating with zero effects. At the end of the day, your oil is doing most of the lubricating on that surface
2. I have also DIY honed cylinders that had gouges much like yours, got new pistons and rings and rebuilt with zero noticeable effects. As long as you are not re-gouging the piston, there is no harm done. Is there a chance of blow-by? of course! but it is minimal and, again, I witnessed no long term ill effects.
3. have you considered Tig welding the gouges and then boring to original diameter? I've seen that done too. I'm not sure how it would react with the Alusil though. (if the block is actually saturated with it)

Just a few thoughts! I'm enjoying the project and I think you are doing all the right things!
1. It's not a silicon application. The silicon is part of the aluminum. 17% actually. The honing is an acid paste with a felt type applicator that removes the aluminum and leaves a silicon bore for the piston to ride on.


2. Are you saying you abrasive honed an Alusil Mercedes (or other) engine block then rebuilt it? I have no experience with that but knowing the technology im fairly certain that's not a good idea, it may work but it's not going hundreds of thousands like a factory engine. Aluminum pistons can't ride on aluminum.

3. This could work to fix the scratch but I'm not even sure you can Tig the Alusil without it going nuts from the silicon present, plus no silicon there in the repair so when the acid home is done it would eat it more than the rest.


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'85 300tdt (sold),'64 220b,'63 220Sb ,85 monte carlo ss 406SBC(4 sale),1976 vega wagon(sold)
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A category 1 piston measures 87.995 mm and a category 1+ is 88.000 mm a difference of .005 mm which in decimal is less than 2 tenths. Five tenths is 1/2 of 1000th of an inch. So the difference between a category 1 piston and a category 1+ piston is about 2 ten thousands of an inch. By those factors it really doesn't matter if I use a category 0 or 1 or 2, the difference is minute. The only consideration will be how much honing the machine shop will do after the sleeve is inserted and rough bored to the initial dimension.

I already bought 4 used pistons on eBay. That's where I got the 2 category 1 pistons and the 2 category 1+ pistons. The machine shop is going to use an .090 sleeve (I believe the actual dimension is .093). The 2nd repair size is +1 mm which is .039 inches so he'll bore the cylinder by something just over 2 x's the 2nd repair size ( .093) and then hone the sleeve to fit the 1+ piston exactly + tolerance in tenths). It should work out fine. The thickness of the cylinder walls is just shy of 1/2" (.500) so after boring, the thickness of the cylinder wall (not counting the sleeve) will be right around .400. Again, it s/b OK. If this were a high compression high rpm high power engine I'd worry about a cylinder wall of only .400 inches thick, but the low power 380 should tolerate that wall thickness without any trouble.

The saga continues. :)
You have zero to worry about with wall thickness. 6.0 AMG engines are 100mm bore in a block with the same bore spacing. A 560sl is 96.5 bore. .400 is a massive wall. A 400sbc center wall at .060 over is like a business card thick.

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1983 380 SL
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2,506 Posts
Discussion Starter #178 (Edited)
In my reading on the topic of ALUSIL blocks I never came across a reference to there being acid in the paste, maybe there is and I just don’t realize it.

The can of AN-30 ALUSIL honing paste I have does not mention acid. Here is what it says it contains...Mineral Oil, Silicon and Calcium Stearate. According to Wikipedia Calcium stearate is produced by heating stearic acid and calcium oxide. Perhaps it’s the stearic acid portion that is considered acidic but I can’t imagine it being too acidic as it is also used as a food additive.

The front of the AN-30 can simply specifies “Silicon Compound”. The way it was explained to me is that the silicon in the paste etches the aluminum from between the hard silicon particles in the ALUSIL cylinder wall which exposes the silicon to the surface which is what the rings will ride on. The microscopic indents between the hard silicon particles retains oil for lubrication but the piston rings never contact the aluminum, they only contact the silicon in the cylinder wall.

The machine shop will be inserting a cast iron sleeve which will then be honed to final size and finished with a standard cross hatch pattern. No AN-30 treatment will be required as the sleeve is cast iron and not ALUSIL. The other 7 cylinders will be final honed using AN-30 silicon compound for not more than 90 seconds and preferably just 60 seconds. What you are looking for in the final ALUSIL hone is a matte finish with no cross hatch. The final hone with AN-30 does not increase the bore size.
 

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'85 300tdt (sold),'64 220b,'63 220Sb ,85 monte carlo ss 406SBC(4 sale),1976 vega wagon(sold)
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You could be right. I was under the impression it removed the aluminum chemically and left a shallow "silicon crystal matrix" (sticks out in my memory) proud of the aluminum to serve as bore surface and oil retainer similar to what the crosshatch purpose is. I have an extremely low mile m119 that has a casting flaw causing head gasket failure and the cylinder wall is an even dull surface. I'm aware the an 30 won't be used in the steel insert.

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