Cast or Forged Pistions

[steve lewis]

Hi all,

Just been reading the factory Technical Specifications small pocket book (76/77 ,911, Carrera 3.0, turbo ,2nd Edition) I brought from Ebay and it lists the Carrera 3.0 as having Cast aluminium pistions I was informed they were fitted with Forged pistions like the turbo ? As my car has a low knocking sound especially. under idle and was told its due to the car having forged pistions. anybody know for sure? this book has a couple of errors re: the Carrera 3.

[David]

I'm not positive, but I don't believe any Porsche's come with forged pistons.

[andyjboy]

David - all '66-'73 911S models + '73 2.7RS & '74-'76 2.7 Euro Carreras used forged pistons.

Steve - as far as I am aware all CIS-equipped 911 models ('73.5 2.4, 3.0 Carrera & SC models) used cast pistons.

[masraum]

Originally posted by 125shifter
I'm not positive, but I don't believe any Porsche's come with forged pistons.

I believe the 3.2L cars came with forged pistons, but I could be wrong. Either way, it's not pertinent to the original question.

[Bill Verburg]

Originally posted by steve lewis
Hi all,

Just been reading the factory Technical Specifications small pocket book (76/77 ,911, Carrera 3.0, turbo ,2nd Edition) I brought from Ebay and it lists the Carrera 3.0 as having Cast aluminium pistions I was informed they were fitted with Forged pistions like the turbo ? As my car has a low knocking sound especially. under idle and was told its due to the car having forged pistions. anybody know for sure? this book has a couple of errors re: the Carrera 3.

C3 and the 2.7 911s from that era all used cast aluminum pistons, as did the SCs

forged was used on some but not all 3.2 Carrera, Mahles were forged, KS were cast

[Geo9146GT]

All CIS/DME pistons thru 3.2 '89 production, except 930 turbos,were cast, whether Mahle or KS. I have this on no less an authority than Bruce Anderson

[Lukesportsman]

Yes, the new Mahle (replacement) are forged but factory were cast unless turbo as Geo states.

[Bill Verburg]

Originally posted by Lukesportsman
Yes, the new Mahle (replacement) are forged but factory were cast unless turbo as Geo states.

Seems to me that Geo repeated my post

[masraum]

I was just going by what I remembered from Frere, but reading it again, it sound like he's saying that the late 3.2L 10.3:1 pistons were forged, but that doesn't mean the US low compression pistons were forged.

"New higher pistons, now forged again for greater strength*, pronvide the increased compression ratio and the valve timing has also been altered by advancing the existing camshafts by 3* to give the folliwing valve timing..." Frere, 6th ed p81

The footnote indicated by the "*" after "strength" says, "Forged pistons had been used in the 2.0-, 2.2- and 2.4-litre 'S' engines, and had last been used in normal production 911 models for the 2.7litre Carrera. The Turbo has, of course, always had forged pistons."