Rering or salvage?

[1fastredsc]

I have this post on the regular 911 forum, but if someone here didn't see it, here it is again.

OK, i am in one pissed off mood. I'm trying to remove the P&C's as one so i can work on replacing the head studs. I spent the past four hours with no success and am ready to start throwing tools and breaking glass. There's no damn room for this ***** without without seperating the pistons from the cyliders which i don't want to do since they are in excellent shape and would be a waste of money for me to do so. Plus i don't have the patience to spend 3k on a new set. (I really needed to vent) Is there anyone out there who's had success at removing them as a pair, and if so what did you do? And if that get's thrown out of the window then what am i looking at as far as rering success probability?

[kstylianos]

fastred,

What type of P/C's do you have? If you this deep into the project, might as well use new rings ($60) and ask Superman the process he used for breaking in new rings in his Aulsil's (if you have them). I think he cleaned them up VERY WELL and used a light coating of Marvel Mystery oil (or equivalent).

If Nikasil, you could get them honed (read previous thread) and use new rings. Break in should not be an issue. If they still show decent hatch marklings, a cleanup may all that they need.

If Alusil, its another story. Porsche does not recommend honing or re-ringing. Some have had success with breaking in new rings w/ Alusil C's, but the process will definitely take longer than freshly honed or new C's.

[1fastredsc]

How do you tell the difference between the two? #'s, cylinder color, etc?

[kstylianos]

The cylinder manufactuer (Mahle or KS) is actually stamped on the sides of the cylinders (either 9 or 3 o-clock) and the cylinder surfaces have different physical properties (color, reflectiveness, etc).

Alusil: Drab, silvery looking. (KS)
Nikasil: More reflective surface and has a goldish tint. (Mahle)

I have a few pictures of each I can post later.

[911pcars]

So what's the problem in separating the piston and cylinder to access the con rod fasteners? The rings should work with their respective cylinder if separated, then reassembled. Just keep paired assemblies marked so you know what goes with what and get a ring compressor for final reassembly.

Sherwood Lee
http://members.rennlist.org/911pcars

[kstylianos]

as promised......

KS Markings:


Mahle Markings:


Alusil Cylinder Wall:


Nikasil Cylinder Wall:

[tgarnoldo]

It also easy to look at the piston, Mahle cylinders use forged piston. These have minimal side skirt. They can be seen in this Ebay listing.

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&rd=1&category=33623&item=2418423800

Arnie

[Wayne 962]

Incorrect. Mahle also used cast pistons. I won a bet on this the other day. Mahle has also made Nikasil and Alusil cylinders over the years.

-Wayne

[1fastredsc]

Ok, kstylianos, you picture helped a lot. My cylinders are definitely ausil, no question about it. My cylinder looks exactly like that first ausil that's posted. Ok, so i guess this leaves me mildly screwed, but one thing at a time, first it's to remove/change studs after luck comes my way and i get the cylinders and pistons out. Thanks guys!

[snowman]

There was once a proceedure for redoing Vega (same as Anusil as far as I know). Is this true and if so why will the same proceedure not work for these? The only reason it wasn't sucessful was the ignortant techs refused to chang their ways to accomadate them.

[911pcars]

If you remove the complete piston/con rod assembly at the crank, you'll have to use new con rod bolts/nuts for reassembly. However, if you merely remove the piston pin to separate the piston from the con rod, you'll have the rods hanging out of the crankcase. This may not be a big deal if you're at home R&Ring the head studs. However, if the machine shop is doing this, they'll want to put the crankcase onto the milling machine table and drill out the studs and/or install threaded inserts. It'll be easier to prep the machining process and seal up all the case openings if the rods are not poking out. So it all depends. Does this make sense?

Vega engines as well as BMW, Mercedes, Porsche 928/Boxster and other engines also used/use Alusil technology. In the case of GM's Vega, the common fix was to bore the aluminum block and install a cast iron sleeve ... or junk the engine. Vega's problem wasn't so much the Alusil, but the manner in which the upper part of the cylinder was supported in the block; there was none. The cylinder was free-standing in the interest of maximum heat transfer to the surrounding water jackets. After a few thousand or hundred miles, the cylinder height receded or distorted causing the infamous head gasket leaks. That and terminal body cancer (rust) were the main reasons why Vegas are now pretty much extinct.

I suppose an Alusil cylinder could be sleeved, but then that might compromise heat transfer or the maximum size of the piston. Some early 911s have Biral cylinders which are aluminum with cast iron sleeves.

Sherwood

[1fastredsc]

You know, if it wasn't enough that the 911 motor has it in for me. My balance shaft belt snapped in the 944 over the weekend.

[Wayne 962]

Well, it could be worse - could be the timing belt!

-Wayne

[1fastredsc]

True, but because of funds i have to drive a 2700 lb vibrator to work for a week before i get paid again. I wonder if i can pick up women with my mobile vibrator .

[john walker's workshop]

just pull off the cylinders. no harm in that. everyone does it. there's nothing that keeps rings from rotating. they go where they want. this way you could at least inspect and align them before reinstalling the cylinders. use the same piston in the same cylinder. if you re-ring, don't hone alusil. remove one wrist pin clip and tap out the wrist pin. then you have access to the rod nuts/head studs. would have taken 15 minutes.

[snowman]

Sherwood,

I was not refering to the sleve operation, but the oringinal proceedure for doing the cylinders. It invloved saving the original cylinders. I do not remember the details nor did I take notes when I was at the presentation that outlined what was supposed to be done, as I had (have) no real interest in doing that with a Vega. Didn't think it would apply to Porsche or I would have.

I am very familiar with the Vega problems as I purchased a new 72 Vega GT. Front fenders had holes rusted in them within the first year. Engine block, as I was told at the time, warped. When it ran it was a bargain, otherwise it was a POS. I sold it in 75 as I was concerned that the whole body way about to break in half due to rust.

My next two new cars were a new 76 Chrysler New Yorker, and the all time POS a new 79 Olds 98 Diesel.This was the last straw in a list of over 25 american cars I owned to that date. I had also had Karman Gias, english crap with a capital C, and assorted forign stuff but no Porsches as of then. Dumb ass me bought a 2002 Denali truck, now I rembember why I should NEVER buy american again. At least my 85 BMW M6 still runs fine.

[Wayne 962]

The rare occasion where I disagree with JW. Walt (Competition Engineering) said the thing to do is to keep them together and put them on a shelf and don't look at, touch, or disturb them. He said that Alusil is very unpredictable when it comes to rings...

-Wayne

[snowman]

Wayne,

I would have to agree with Walt. Let them go the way of the Vega.

[Wayne 962]

Hmm, perhaps I should have been more clear. Walt said to put them on the shelf and leave them there until you're ready to reinstall them on the engine. Don't touch them in the meantime...

-Wayne

[snowman]

OH in that case I don't agree with Walt. But I still say let them go the way of the Vega.