Piston ID help...and cylinder

[speedo]

Getting ready to sew up a 2.7 engine and have questions concerning

Pistons: top of pistons have markings that are either "A A2" or "A2 2"....what do these markings mean? I have a second set of pistons with no top markings, but the insides have 090208, 935, 1275. Are some of these the early 8-1 CR and some the later 8.5 CR?

Cylinders: the markings on the outside bottom of the skirt is a triangle with a "6" inside and either a 1 or a 2. Do these represent different height groups? The cylinders that corespond to the second set of pistons above, are alusil and have only the markings "854/1A+ or 854/2a+.

Combo question: my best set of cylinders are the set with the 6 inside the triangle and the 1 or 2 on the skirt...if these are the same height...the one with the "1" appears to be nicasil. I realize you can't run nicasil pistons with alusil cylinders, but can I run an alusil piston with a nicasil cylinder?

I have basically the 5 alusil cylinders w 1 nicasil cylinder and the 6 good alusil pistons with the "A A2" and "A2 2" marks. As these are my best , will these all be compatible with each other.

Or if not, am I forced to run the cylinders "854/1A+ and 854/2A+" and the pistons with the 090208-935-1275 that I know are all alusil.

Thanks for any guidance

[tom1394racing]

Lars

You can't run Nikasil with Alusil and you can't mix Alusil P&C's with Nikasil P&C's in the same engine.

The number in the triangle on the cylinder denotes the cylinder ht group. Generally speaking, cylinders must be of the same ht group on each bank of the engine.

There are several variants of the 90mm CIS pistons. The CR can be either 8.0 or 8.5 and the piston can be made of either Alusil or Nikasil.

I've got a reference listing of the piston part numbers and several boxes of each type. I've also got spare Alusil cylinders if you need some.

I'm not on my home computer right but sometime tomorrow I'll post the reference listing and some pics.

[speedo]

Tom,
Thanks for repsonding. For clarification, I know I can't mix and match the nicasil (N) and alusil (A) in the same engine. My shop that helped with a case line bore told me I could run an A piston in a N cylinder. I have a complete set of A p and cs...I just need to id the pistons so I am using the 8.5 pistons. Here are the pics of the three different pistons
All CIS and 90mm





The two on the let are similar withe the variation on the "A A2"and "A2 2" markings, while the one on the right has what looks like a "1" and perpendicular to that is a small "2". The first two also have abreviated skirts and the third has a more full skirt.

Suggestions are appreciated...I just basically want to use 8.5 pistons.

[speedo]

I was surprised to find that after I had aquired the plug and tap for the oil bypass mod...that my case didn't need it. I thought all 2.7 cases needed it?
I thought that Porsche didn't incorporate the mod until the 3.0 7R cases.
This is obviously a 1977 case. I'm glad to not to have to do it, but I checked the other 7R 1977 case and it is not done?

[tom1394racing]

Lars

Here's the best information I have on the 2.7 CIS piston types.

Engine size Mfg CR P/N
2.7 CIS 90mm KS-Alusil 8.5 90202
2.7 CIS 90mm KS- Alusil 8.0 90208
2.7 CIS 90mm Mahle-Nikasil 8.5 90L58
2.7 CIS 90mm Mahle-Alusil 8.5 90L61

If you need any of these or 90mm cylinders (Alusil or Nikasil), let me know

[sww914]

They changed the oil route mid-'75. My case needed it but my friend's later '75 didn't.

[euro911sc]

Speedo,

Note that there may be different diameter groups as well so if you are mixin' an matchin' be aware. I had this issue on my 3.0, though I am not sure it extends to the 2.7... just thought I'd mention it.

Best regards,

Michael

[tom1394racing]

Porsche "classed" the piston and cylinders by diameter groups to make it easier to assemble pistons and cylinders in matching pairs with the correct clearances at the factory. Classes were 0, 1, 2 etc. At the factory, the technicians would make sure they used pistons and cylinders of the same diameter group.

When matching used pistons and cylinders it is necessary to measure the piston and cylinder diameters to ensure proper clearance.