JE pistons on standard cilinders (100mm)..which gap/tollerance?

[dan67]

Hi, i have big "drama", JE pistons on 100 mm standard barrels (964 3.6 on 911 body) i have measure over 22/100 the gap!!! very very big...but if possible normal for JE...can you tell me something!
thanks/GRAZIE!

dan

[KTL]

Just received a set of JE pistons for my 98mm cyls and the instruction sheet that accompanied them says the piston-cylinder clearance should be at minimum 0.0030 inches

Is the 22/100 you state actually .22mm? .22mm is 0.0087 inches which is still quite a lot of clearance.

[Bob Kontak]

Got to get these numbers figured out. 0.003 is three thosandths of an inch.

22/100ths of one millimeter is 8.8 thousandths of an inch.

Pretty sure JE is a little sloppier than original tolerances but don't know the specs.

[KTL]

Whoops.... Thanks for the correction on my description Bob. The number is correct. I just stated it in words incorrectly.

Max P-C clearance (wear limit) per the older 78-81 Porsche spec books is 0.15mm (0.0059") for Nikasil and I recall the newer '84-'88 spec book I have stating the min was reduced to 0.12mm (0.0047"). Wayne's rebuild book says 0.15mm is 75-81 and 0.12mm is 82-89

New installation spec is generally 0.025mm to 0.042mm for Nikasil/Mahle from 74-89

So .22mm is well beyond even the older max P-C clearance allowance.

[Mysterytrain]

Dan, It will run but it will smoke everytime you start it. I would get the correct sized pistons.