2.7 CIS Pistons US or EURO

[9magazine]

We are considering the use of new pistons in our 2.7 rebuild for 9 Magazine. The pistons don't need to be replaced, however, many of our readers have the Alusil pistons and need to replace them if doing a rebuild.

The options for replacement pistons and cylinders are a US spec set and an Euro spec set. Are there any performance gains from the use of the Euro set, and are there any potential problems using them in a US 2.7 Carrera engine?

Thanks,

Brian Minson
9, The DIY Porsche Magazine
http://www.9magazine.com

[CARRERIC]

Brian,

I am at the same crossroad. I've been following your rebuild on the 74 Carrera. I have a US 1975 911 Carrera (2.7L). The car is at the shop having the motor rebuilt. I decided instead of recond the old pistons I would buy new. The price difference was not that significant. I decided to go with the RS so I have more options later on. The US pistons were made for CIS, and swirl the gas different. However my mechanic says the RS will work great with the cis and are stronger pistons.

Eric

[Wayne 962]

Euro CIS versus USA CIS is the question. The Euros are higher compression, which is better, with limited or no side effects...

-Wayne

[9magazine]

Wayne,

What would be those side effects from the Euro CIS P&C?

Brian Minson
9, The DIY Porsche Magazine
http://www.9magazine.com

[Wayne 962]

There really aren't any. The Euro cars had fuel injection that was tuned differently, but I don't think that would make any difference with the P&Cs. Higher compression pistons - I believe if you are running a lowered deck height or a more agressive cam, you might have increased clearance problems. 99% of the time there are no side effects.

-Wayne

[Wayne 962]

Okay, wait a sec - I made some silly mistakes here. I was thinking of the difference between the USA and Euro 3.0 cylinders - I didn't read the post carefully enough - I didn't think you were talking about the 2.7 ones.

The two variety of 2.7 pistons come in 911 and 911S. The S pistons are higher compression than the 911 pistons. I do not think that there is a difference between USA and Euro (I looked this up and couldn't find any indications of any differences).

Now, if you're talking about the Euro Carrera, it has the same engine as the '73RS which is a completely different design...

So, I guess I'm confused about the question of Euro vs. USA as I don't think there is a difference on the 2.7 CIS models...

-Wayne