Can you just do 1 cylinder ?

[Tori]

Maybe a dumb question, but in my current tear down for valve guide repair i found #6 is badly scored. I feel like things just got a whole lot more expensive, but can you just repair one cylinder ?

I'm an air cooled newb so don't know if one can just sleeve this cylinder, or buy another stock cylinder and fresh piston and continue on with life, or is that just a crazy idea ?

All the other cylinders look great.

[Eagledriver]

No reason you couldn't just replace one. The trick is finding a cylinder from the same height group and matching the weight of the new piston to the others. There are markings on the cylinders that tell the height. If it were me I'd look for a used piston and cylinder or maybe a used set. You can take weight off a piston pin to make the weight match if the new piston is heavier

-Andy

[tocobill]

Yep, like about just need to match the height group so that your shims are the same. Hard to judge form the pics on how deep the damage is. IF its scuffed then you could probably re-plate and hone. If it needs to be replaced just post a WTB or call EBS, Henry, or Steve and see if they have a cylinder that matches the height group.

Have you measured the cylinders? Are the still within spec or do they need to be replaced? If its due for a rebuild it could turn into slippery slope of while your in there.

[Tori]

OH great, thanks guys. I was hoping that was an acceptable repair. I've done personal water craft jugs like this before and it was an approved method so was hoping it was allowed here too.

I'll try to measure tomorrow. I think the boss has dial indicators that'll measure things. If not, i know a nearby guy that should. Anyone know the spec. off the top of your head ? 87 3.2 ? I can look it up so don't go out of your way if it's not already in your brain.

[tocobill]

This is what i have out of a Bentley manual for 84-89.

[fanaudical]

Yes - That's why Porsche made them all separable.

[earossi]

It's probably more cost effective to have the bad cylinder sent out for replating and then honed to size. Bigger issue will be getting a piston that is the same weight. If possible, send the piston out with the cylinder, so that the bore is finished to properly fit the new piston. Get a piston that weighs more than your damaged piston and then you can remove weight from the new piston until you match weights with the old piston.

[DRACO A5OG]

Brother Tori, send the Wrist Pin as well for polishing.

[Rawknees'Turbo]

Tori, guys here like Bruce (Flat6pac) and CGarr (Craig), usually have many pistons and cylinders on hand to choose from and I bet their pricing is very reasonable (don't know for sure about cost - just going by their reputations here). I would definitely contact those guys before having that one repaired.

[Tori]

Thanks to all that have offered advise and the tech spec. (tocobill) I'm in a much happier place now with those options. When i first saw that cylinder today i said to myself, "well, you just spent $3000"

I think i'll dash out to the shop and get my micrometer and see what it says.

The heads are going to cgar, so i'll talk to him about a used slug and jug

[Tori]

Using a std. mircometer (yes, i know that's not the correct tool - but it's all i have until tomorrow) i can only measure down 20mm. (not the required 30mm) but with that, i got 94.86mm. My cylinder has a " 2 " not dots as indicated. So i assume i use the 95.014-95.021 spec. I guess what i'm seeing is a good thing at this point. The other cylinders do look very good, perfectly smooth everywhere, and no visible patterning.

[DRACO A5OG]

Let's hope for the best

Try to take the measurements at the groove/s to get an idea how deep it is/are.

BTW, do you see any cross hatching?

[Tori]

I was measuring the good cylinder. I'll let a pro decide on the bad one.

No cross hatching. Do these cylinders normally show that from stock ? I don't even see it in places the piston doesn't travel.

[DRACO A5OG]

Hmm? maybe not since mine was rebuilt 187K miles ago and it had cross hatching. I know that PAG used two types, one did not have cross hatching from what I understand.

[stownsen914]

I saw one suggestion to replate the cylinder. But is it Alusil? Nothing to replate in that case. And the scoring looks pretty bad anyway. If it's Nikasil it may be possible if the scoring isn't too deep.

Make sure you figure out why that cylinder had this scoring happening. If you just replace/fix it, you may wind up having it happen again. Bad injector? Piston squirter not working? Etc.

Scott

[Tori]

Thanks for that info Scott. I don't know the difference between Alusil, or Nikasil cylinders. How can i I.D. this one ?

I've not identified what caused this failure, any tips on figuring it out ?

[KTL]

The cylinder interior color is grayish. That's a sign of Alusil cylinders. Nikasil are slightly yellowish.

Also take a look at the lettering on the side of the cylinder. Mahle nikasil clearly say Mahle and KS alusil cylinders have a "stacked" KS logo like this.



Used KS piston & cylinder sets are pretty common and sold rather cheaply. So maybe you can get a complete replacement set. Seems like a lot of people ditch the KS stuff and get new Mahle or they'll have the alusil cylinders plated with nikasil and use JE or CP Carrillo pistons in them. EBS Racing is well known for providing this service of "converting" Alusil cylinders to nikasil. Not sure if they use US Chrome or Millenium Technologies to do this plating

Make sure your measurements are very precise (use an actual bore gauge with a 0.0001" resolution dial indicator) because the clearance between the piston and cylinder are very tight. If you're not measuring accurately, your clearance can be way off and you'll have a bad situation on your hands rather quickly when the engine is run. That is, if your clearance is too tight. If it's too loose, that's not good either. But much better than being too tight!

Edit: By the way I have the '84-'87 factory Porsche tech spec book in electronic format that you can download. Shoot me an email and i'll share it with you from my google drive.

[Tori]

Thanks Kevin, i agree this appears to be the Alusil. Neither brand names are seen though.

I'm not concerned with measuring this one. I'll let the machine shop it goes to do that. Most likely though i'll just try to find a good used one that matches.

[Rawknees'Turbo]

Tori, another guy that might have a proper piston & cylinder combo is Henry Schmidt of Supertech - he posts here (you've probably seen him) and has said in the past that he has shelves full of good, used Alusil gear.

[Tori]

Sweet ! Thank you sir.