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JFairman JFairman is offline
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Join Date: Jul 2006
Location: S. Florida
Posts: 7,234
I've heard the rings gaps "migrate" too. I'm not a pro engine builder, I've only built some of my own engines starting with horizonatal shaft Briggs and Stratton lawn mower engines for mini bikes when I was a kid and then BMW 2002 and 635 motors 25 - 35 years ago.
A few months ago I rebuilt the top end of my 930 motor and I have a PDF copy of the factory workshop manual you can download online.

Here's a jpeg of the page from it showing the correct position of the ring gaps for a 911 motor. I installed my new Mahle pistons and cylinders with the ring gaps positioned like this and when I took the pistons out that were installed by a Porsche shop around 35,000 miles ago I was surprised they were pretty much in these same positions.

Top compression ring gap: 4 o-clock, second compression ring gap: 10 o-clock and the oil ring gap at: 2 o-clock.
Anyway, it's working good like this

Old 07-26-2014, 03:47 PM
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