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I'am in the process of rebuilding my 951 engine - I got to the honing to size, lapping and exposure stage and I would like to share the experience I had.
Here in my country I found only one machine shop witch previously honed Alusil cylinders. They use the KS system witch changed over time. In the past KS used exactly the same method as Sunnen and it's the one described in the workshop manual. They provided a tool for every stage of the job and they even had a brochure with detailed instructions for more engine blocks including the 944 and 928 engine blocks. For some time now KS switched to a new method, witch they say it's used in series production. This new procedure requires only two tools (apart for the diamond cutting tool for rough cutting). one it's the honing stones ( also does the polishing) and the other it;s the exposure stone ( witch does the job of the an-30 paste and felt strips). Since the time for exposure with the new stones it's not specified anywhere I calld KS and the tell me that the time for exposure it's 10-20 seconds and it's good if I hear some squeaking noise.
After exposing for 120 seconds it's still a bit shiny.
First thing I was thinking after I got the block back from machine shoo was exposing with AN30 paste ( but it's a pain to get some here), and since I don't have a Profilometer to check the surface I took some photos of the cylinder surface.
I'am in the process of rebuilding my 951 engine - I got to the honing to size, lapping and exposure stage and I would like to share the experience I had.
Here in my country I found only one machine shop witch previously honed Alusil cylinders. They use the KS system witch changed over time. In the past KS used exactly the same method as Sunnen and it's the one described in the workshop manual. They provided a tool for every stage of the job and they even had a brochure with detailed instructions for more engine blocks including the 944 and 928 engine blocks. For some time now KS switched to a new method, witch they say it's used in series production. This new procedure requires only two tools (apart for the diamond cutting tool for rough cutting). one it's the honing stones ( also does the polishing) and the other it;s the exposure stone ( witch does the job of the an-30 paste and felt strips). Since the time for exposure with the new stones it's not specified anywhere I calld KS and the tell me that the time for exposure it's 10-20 seconds and it's good if I hear some squeaking noise.
After exposing for 120 seconds it's still a bit shiny.
First thing I was thinking after I got the block back from machine shoo was exposing with AN30 paste ( but it's a pain to get some here), and since I don't have a Profilometer to check the surface I took some photos of the cylinder surface.
Hi.
For info I did the same work on an engine with a company that also used the sunnen method priveously and now used the method you describe.
My engine failed with scored bores after only 500 km. Inspection showed measurements and clearances to be ok so bore prep was probable cause of failure. It was however never fully determened what caused the failure I had since many variables influence. The Sunnen method is "self limiting" as I understand it and the "production" method is not and in a non controled environment (carefully measured) I guess its easy to overdo it resulting in that the silica is not exposed enough. My bores also looked shiny.
For info I did the same work on an engine with a company that also used the sunnen method priveously and now used the method you describe.
My engine failed with scored bores after only 500 km. Inspection showed measurements and clearances to be ok so bore prep was probable cause of failure. It was however never fully determened what caused the failure I had since many variables influence. The Sunnen method is "self limiting" as I understand it and the "production" method is not and in a non controled environment (carefully measured) I guess its easy to overdo it resulting in that the silica is not exposed enough. My bores also looked shiny.
//PF
that's reassuring. I do heard about this. in fact that is why I'am questioning so much the finish of the cylinder wall. Can you tell me what might have been the other variables that lead to bore scoring. Do you also have a picture with the scored piston?
I also saw that if I use Mahle powerpak pistons 100.50 bore size does not work for all the pistons in the set.
For example Mahle says that minimum cylinder to piston clearance in 0.09mm and one of the pistons in the set measures 100.425 mm resulting that it needs a 100.515 bore to be on the minimul clearance.
I will try to find and old block with a good, factory prepared cylinder and take some pictures to have some comparasion. Does anyone have any ideea where to find some AN-30 paste in Europe ( except Romania Sunnen dealer)
I will try to find and old block with a good, factory prepared cylinder and take some pictures to have some comparasion. Does anyone have any ideea where to find some AN-30 paste in Europe ( except Romania Sunnen dealer)
I sure don't know, but if you commit to doing this the original way and you can't find it, I'll source you some here and ship it to you.
I would have a partial can on hand but I leave it with the machinist that used to do my blocks.
I'm interested in buying a can of an30 also if someone is kind enough to buy it and send it here.
Alex: awesome idea with microscope. I'm looking at used microscopes right now.
My cylinder walls look completely dull after AN-30 massage. Left is AN30 massaged, Right is like it came out of machine shop. (they said its how it's supposed to be).j
I have seen a few NOS and reworked Alusil bores on engines that still run strong today and they all had a somewhat matt finish with zero scratch at all.
Those bores definitely do not look how Alusil bores should.
Thank you. I tryed to buy from Goodson last year but they redirected me to their local Sunen dealer. I'll keep in mind and in case I won't find here I will send you a message.
I'm interested in buying a can of an30 also if someone is kind enough to buy it and send it here.
Alex: awesome idea with microscope. I'm looking at used microscopes right now.
My cylinder walls look completely dull after AN-30 massage. Left is AN30 massaged, Right is like it came out of machine shop. (they said its how it's supposed to be).j
Also no hone like marks/scratches visible.
I also did buy the microscope for this job. I used 4x Objective with 10x Eyepiece (ocular) resulting in a 40x (4x10) magnification. I also had a 10 objective but the focusing distance it's almost zero and since I can not place the microscope perpendicular to cylinder wall I can not focus with that.
If you buy a microscope I think the best one would be one that you can fit inside the cylinder in such a way that the objective it's perpendicular to the cyl wall.
09-12-2017, 05:36 PM
Cylinders honing to 100.50
that's reassuring. I do heard about this. in fact that is why I'am questioning so much the finish of the cylinder wall. Can you tell me what might have been the other variables that lead to bore scoring. Do you also have a picture with the scored piston?
