pistons

I have a 79 911 3.0. the pistons have a high dome to one side the shape of an egg. My questions are one are these stock ? if not how much hp do they add ? and is the piston installed so the dome portion is oposite of the spark plug ?

Difficult question to answer without a picture of the pistons!

If you can find someone with a set of the official workshop manuals, you'll find a section in the engine suppliments that shows photographs of all the various types of pistons.

Typically, the CIS pistons do have a large bulge on the exhaust side of the piston, and a smaller "cut-away" on the inlet side which promotes tubulence. This is sort of orange segment shaped.

Another good guideline is the word MAHLE on the inside of the piston is on the exhaust (down) side.

Hope this helps.

- roGER

Bruce Anderson's "Porsche 911 Performance Handbook" has pictures of just about every imaginable piston. If you've got the piston out of the engine, you probably should own a copy of this book.

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Greg
72 911S

Thank you guys looks like ill be looking for two things one the mahle stamp and two Bruces book. Thanks again