New rings ?!
 

Ok, the question is not new and the debate will probably go on.

I got a thip two install new rings and two (2) cylinder gaskets on each cylinder. The extra gasket should then prevent the rings to break at the "turn-point" as the distance will be slightly shorter.

I am not sure what to make of this tip. Any ideas ?

If I understand your tip; by installing additional copper gaskets under the cylinders, this increases the space between the top ring and the "ridge" that forms on used cylinders, thus preventing ring breakage. Have I got that right?

If so, you could avoid this maneuver by having a machine shop remove the "ridge" from the cylinder. BTW, if there is significant ridge on a standard cylinder, your piston-to-cylinder clearance may be borderline. Have this dimension checked as well. The engine will be noisy and not last as long.

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

What ridge? Have you looked at a used Nicasil cylinder? I've only seen a few but I've never noticed a ridge aside from a little carbon. These cylinders have a very hard surface. All the used ones I've ever seen still have the original cross hatching marks.
I would reconsider any other "tips" you receive from this source.
-Chris

Even if a ridge formed (which I'm not saying it does), this wouldn't make any sense, since the ring would be bumping up on either the top or bottom 'ridge' and cause vibration to the ring...

-Wayne

Generally speaking, you only see a ridge on the top of the cylinder and a taper as you travel down the cylinder bore. The additional shim sounds like a band aid approach since you'll likely be reducing the compression ratio with the lower deck height, yes?
my .02 cents

Dave

There's no reference whether this "tip" was for cast iron, Nikasil or Alusil cylinders. I'd say this mostly applies to cast iron cylinders which is a softer material than either Nikasil or Alusil. The "ridge" is more distinctly formed at the top due to exposure to the combustion temperatures, corrosive gases and lack of lubricating oil. The operating conditions at the bottom end of ring travel are not as severe.

Sherwood

To clarify, I have no clue if this is a good way to do it or not, jus seeking your opinions. :) I always listen to other people and then make up my own mind. ( I will reuse my rings as everything is within spec )

Rings are cheep compared to taking the engine apart to change them, very cheep. Cylinders MUST be honed for new rings to seat properly, and the cylinder and piston must be in spec. There is always a ridge, if you cannot see it you are not looking hard enough or do not have the right tools to measure the cylinder. If you install new rings without removing the ridge you will have big problems, probably broken rings within seconds or a few thousand miles at most.
You can buy a cylinder hone for about $50 ( the silicone ball type is best ) or have a shop do it for about the same price.
If you reuse your rings, its ok to do nothing But you must put the everything back in the exact same place it came from. If the rings have over 20,000 miles on them I would never reuse them and I am cheeper than cheep.
People and shops that use tricks like you are discribing are the ones that give auto shops a bad name, they are just crooks,or stupid or both.

A cutting tool is usually needed to remove ridge from the top of a cylinder. Cylinder honing devices aren't designed to do this ... portable types anyway. Perhaps a rigid honing tool on a fixture might do it.

Sherwood

I am assuming that the ridge is very very small, like discribed. If it needs a ridge reamer its out of spec to reuse as is. A rigid, stone hone, requires skill to operate if you are going to do more than deglazing. Aquiring the level of skill on a single engine is unlikely.
Chances are the cylinder is no longer perfactly round, even if its in spec, and new rings, which are perfactly round, will never seat properly. A machine shop can hone the cylinder back to round, but it is unlikely it will still be within the original spec. On newer engines the piston/cylinder fit is only ONE thousandth or less on some models. An old engine might allow for a one or two thousandth inch increase in bore size without any consequence.

The least expensive way, other than using the original rings on a low mile engine,is to get the next size piston, with new rings, and have the pistons bored/honed out to match..

correction not PISTONS but CYLINDERS bored/honed

Chances are brandett's SC motor has Alusil cylinders, in which case honing is not an option.

Even for as little as 1 thousand hone?

Snowman,
AFIK you don't usually hone or bore a (non-iron) Porsche cylinder to remove a little material. If you remove material you must replate them. Even if you could remove a thou, "over bore" pistons are not available off the shelf.
I've measured a (very) few 911 cylinders and they do wear oval but the wear is still minimal.
-Chris

I'd love to hear one of our Porsche shop people weigh in on this. They're the ones who have seen dozens of engines, while us hobbiests get to see a relatively few. That being said, I've rebuilt a bunch of 1970's 911 engines and have **never** seen or felt a ridge, even on engines than have had over 200,000 miles on them. This includes T's with cast iron cylinders, E's and an Alusil 2.7. It has always surprised me, because my experience with older U.S. engine blocks is that there is **always** a ridge.

By the way, a finger is a pretty good (amazing, really) ridge sensing tool. You can easily detect fractional thousandths just by runnning your finger lightly over a surface.

The 2.2T I took apart had ridges, very definite ridges in the cylinders. Don't know the mileage. I honed about 0.0005 to get them back to round.

PS A bore guage that measures 0.0001" is a big help in measuring this. I also clamp the cylinder in a fixture that simulates the head. Torquing the bolts to the same as the head is torqued to is highly recommended. THe resulting cylinder will break in within the first 5 minutes of running. How to tell the thing really sealed right? It should spring back when on the compression cycle when you crank it over by hand, IE feel like cranking on a spring.