C4rrera

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!

kromdom

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

C4rrera

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.

kromdom

LN Engineering
MB Motorsports
Flat 6 Innovations

check out post #316 in the BLOWN ENGINE link. Best of luck.

alpine003

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?

C4rrera

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.

C4rrera

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.

Ahsai

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.

Imo000

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.

C4rrera

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.

Imo000

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.

C4rrera

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...

C4rrera

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

Ahsai

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

george_west

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.