J&E forged pistons (smoky engine)

[Alan.UK]

Just a quick questions. Do J&E pistons cause excessive smoke until they reach operating temperature and the clearances are correct?

Has any one else used J & E pistons, these ones are 85 mm (I believe in a 2.4 E) with approx 20 k on them. On start up it is very smoky, but the leak down readings are all low between 2-6%

Any advice

Alan

[Scott Clarke]

Alan-
I would think that the pistons are not the problem. Smoke upon start up is a clasic 911 trait. It seems to be an issue with valve guides and valve guide seals. Because these sit low in the engine, oil tends to collect there and seep past the seals. This collected oil, either in the intake or exhaust ports or even in the exhaust system, is likely what is burning when you start the car. Worn guides mean that the seals have a hard time doing their job, but even with brand new guides, some seepage is likely. Viton seals are said to be better than most at preventing this problem.
-Scott

P.S. Note that seal problems would not be evident in a leakdown test.