Pistons & Cylinders Placement in Original Positions
 

My engine is a 2.4 911T engine and it needs a rebuild. I would like to understand well why it is important (or is it?) to make sure to label pistons and cylinders when tearing down an engine so as to be able to make sure to put them back in their original positions when reassembling an engine. I mean, isn't it possible to use different cylinders and/or pistons, new or used, or mix and match used cylinders with another set of new or used pistons? Imagine wanting to upgrade a 2.4 liter T engine by buying a set of good used 2.2 liter S pistons from one source, and a good used set of cylinders from another source (2.2 and 2.4 cylinders are the same at 84mm right?). I would have thought it would not matter at all where each part could be placed, particularly when using a set of new piston rings. Can anyone explain the ins and outs of this to me? Thanks!

All original 84mm 911E or 911S cylinders are of Biral construction, which means they have aluminum fins cast around a cast-iron liner. As such, whenever the pistons come out of the bores, whether for new rings or to replace the pistons, the cylinders must be honed.

The 911 T cylinders are all cast iron, same honing, but these don't have very good heat rejection so are not recommended for use with E or S engines.

So it doesn't make a difference if you mix and match. Perhaps you have heard this about the later Alusil cylinders, which are generally not re-ringed (big debate, search here) and so after inspection the same pistons are put back in the exact same cylinders because they have run in together.

OK, not to hijack this but does this mean I don't have to religiously track p/c matchup on my nikasil 3.2? I was worried about the shop mixing them up when they get them for a check up.

I would try to keep everything matched remember if your engine has a mismatched set of P/C it could be very dangerous to mix them specifically if you don't check piston size to make sure it matches cly. size. If you put a #2 piston in a # 1 cly. you will be in trouble...

This also important if you have two different height groups you will run into cam binding. I guess if you are using used parts I try to put them back in there original orientation.

I'm sorry, now I'm confused. First, I was told by a reputable person that Nikasil cylinders never need to be honed, only scrubbed clean. Second confusing point for me: What do you mean cylinder 1,2 ,3, etc.? I mean, I unerstand you are referring to the position on the engine, but are not all cylinders identical? I mean, a number one cylinder refers to its far rear/left position on the engine, not a specific shape or anything else, right? I think if they were different in any way, it would mean the pistons would also have to be different too. You can't put a square peg into a round hole, right? Thanks.

What I was trying to explain was that the piston has to match the cly. you have 0 group cly. you have to use a 0 piston.....I believe that everything needs to be returned to it's original place. Why I said what I did is as a warning if you have never done this before and removed everything with out marking the pistons and cly. threw them in a box then went to put it back together and didn't notice that there may have been a difference well that could be a problem....this is why I mark everything and put it back where it came from.

sorry for the confusion

Oh. OK, thanks! Looks like I'm more of a novice than I thought. What's a 0 group cylinder?

this is an example...


http://forums.pelicanparts.com/uploa...1202524518.jpg

The honing recommendation was for Biral cylinders (steel liners), not Nickasil.

-Andy