Honing and Re-coating Cylinders

Hi Guys, Quick overview, I've been kinda lurking for awhile but this is my first post. The information here has been immensly helpful, there are some great minds here. I purchased a roller 996 last fall. Over the winter tore down the motor for a rebuild. The motor ran well when I bought it, but had non ferrous metal in the oil filter. The previous owner also informed me he last oil pressure for a second. Shut down the engine and put it on a trailer. I found the remnants of a cam chain tensioner guide in the oil pick up, the plastic was most likely the culprit. I did not want to risk it and opted for a tear down. Work travel has delayed progress, but now I'm back at it. This is a project, my first porsche. I wanted a challenge, and I think I found it. When I split the case I found one of the cylinders had a score in it. Besides that, every cylinder was flawless. Looks like it was caused by one of the oil rings actually, even though there is no evidence of a damaged ring. To my question: This is a project, not a money pit. Does anyone have experience with honing the coating out of the cylinders and recoating them? Matching to the pistons of course. I have found a company relatively local that claims a lot of experience in recoating porsche cylinders, and are very reasonable. I'm just looking for opinions on the positives and negatives. I would do all 6 cylinders. And re-coat the piston skirts. I attached pictures for reference. Thanks!

a few threads about engine tear downs/rebuilds, one of the most current ones: https://rennlist.com/forums/996-foru...wn-engine.html and one specifically for scored cylinders: https://rennlist.com/forums/996-foru...k1-or-mk2.html

Thanks for the links, I did read through both those previously, well not all 37 pages, but most. The company appears to offer a service similar to hartech. I'm really wondering why I haven't seen more of it. People mention it from time to time on here.

LN Engineering MB Motorsports Flat 6 Innovations check out post #316 in the BLOWN ENGINE link. Best of luck.

Please keep us updated if you decide to try the recoating. I don't know too many that have gone this route. BTW, how do you manage to find time to even work on the Porsche with the Fiat, bobber, and piano?

Thanks. There is a little info there regarding resleeving, but thats not what I'm referring to. I'm talking about what they did here: https://rennlist.com/forums/928-foru...plating-4.html Although this is not a good example, I was trying to find information and doing a similar thing in a 996 motor.

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It is tempting. I'm trying to gather as much information as I can before I make a decision. Haha. The Fiat was last summer, the bobber was last winter, and the piano well, its not mine. Long story ha.

Addressing the cylinders is a major cost and the proper fix is resleeving. The choices are iron and nickies. There are lots of material about the two if you search. I chose nickies because it's proven and Jake Raby uses it on all his engines.

That mark wasn't left by any of the rings, it goes passed where the rings stop at the bottom of the bore. Something either got caught between the piston and the cylinder or the piston intself caused it. You have a picture of that piston handy? What do the conrod and main bearings look like? If the piston is still OK (not great but OK) and depending how deep that mark is, you could put it all back together and just keep an eye on the oil. BUT considering you don't know how bad the oil consumption was before, this might be the last least expensive option. I have my engine is apart too at the moment but for a different reason.

Thanks for the reply Ahsai. I understand resleeving is the tried and true method. I'm just exploring my options. I'm willing to try something different if its viable.

Unfortunately I don't know anyone that makes oversized pistons that can be used just by boring out the cylinder. Sure would be nice if someone made them.

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Very true. Thanks for the insight. I will post some more pictures this weekend. The piston did not have any damage besides a slight glaze in the respective location. Ill also get some pictures of the bearings. That is the reason I tore down in the first place. I have considered putting it back together like this, but that would be tough. To do all this just to have a picture of the score in the back of my mind...

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I plan to use the stock pistons. The plating process allows for use of stock pistons and oem rings.

This is a good read https://rennlist.com/forums/996-forum/550974-lokasil-beyond-50-000-miles.html

I believe the reason re-sleeving is necessary, as opposed to replating, is due to roundness. You can only correct out-of-round so much with replating and hone. Might be worth looking into though. Maybe ask the plating service how much out-of-round is acceptable for replating and returning to stock bore size.

Oil consumption- Until you measure for ovality and taper, isn't the idea of just slapping it back together a little suspect ? If you do reassemble, be sure to place all the rings back exactly where they were on each piston & bore. If you muddle them up , or use new rings & have bore/taper, you certainly will have an oil consumption+compression issue.

Yes everything would be fully inspected before it went back together even if I left the score. The question really isn't what would need to be done if I was to leave it, I'd cross that bridge when I've reviewed all the options. It's more the viability of replating the cylinders of these motors assuming they check out as a good candidate for the process.

Have you decided to proceed with replate? Would the bores be Nikasil, same as gt3 or turbo?

Usually not an option, due to cylinder taper, and ovality being well outside the safe zone. The wear surface is just one consideration of a cylinder.

The plating is very similar to Nikasil, called Nicom. The supplier claims it is compatible with all rings designed for use with Alusil or Nikasil. I am currently in the process of discussing how they would go about evaluating the cylinders as good candidates for the process (roundness, taper), expected life cycle, warranty, and any available referrals for other watercooled porsches.

U.S. Chrome.... They have good sales people. Been there. Done that.

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So Jake, That was the point of this post. What was your experience?

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Please email me at [email removed]

Hartech in the uk are the best guys at honing cylinders, they fit a strengthening ring on the top of the cylinder which actually pulls it back into round then re hone the cylinder, if the scoring is minimal it may be able to be honed out, this is a lot cheaper than sleeving which they also do if it's too bad, I think they charge something like £80 per bore for the process, this protects again a D chunking also and there are also some mods done to the coolant galleries, this might be viable for you to ship them over , you can re use your stock Pistons, I did this to mine, it also means you can fit new rings and they will bed in ok not trying to run in an oval bore , I can't find much about the process on their website to give you a link but if you call them and speak to grant he will sort you out he's very knowledgable !!

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Thanks! I've also been looking into Hartech, I've seen some good reviews around here and other forums.

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So how long or how many miles have you put on since you had this done? Do they offer any kind of warranty on their process? Sounds like another viable alternative.

Yes it's another option if you are doing a rebuild and your bores are OK as in no scoring and you maybe have just a bit of ovality and taper as they all will. It's a cheaper way to at least do something with them and get just as good results, then be able to fit new rings and strengthen against d chunking. They are good guys there and will always help!! I would imagine they will stand by their work but if it's part of your own build there's only so far they would go I would expect, they do offer full builds also with warranty and various upgrades are available similar to what jake offers. I just found the re rounding process really helpful with my budget as sleeves can really give you a kick in the er wallet!! They get the bores back within an except able tolerance , the special honing tool is just made for these type of bores which also re finishes the bore to a factory finish and the ring removes the chance of d chunking so if your bore isn't damaged, light scoring can be worked with but obviously if it's knocking like hell your going to need a sleeve, they do a really heed sleeve also which is like the ones in the metzger engine , nikasil plated aluminium, they are very nice but obviously a lot more money!!