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Jim2 Jim2 is online now
7.0:1 > 11.3:1 > 7.0:1
Join Date: Oct 2003
Location: Calgary
Posts: 2,146
Granted this appears to have been done on the RCT, someone should measure the dome/crown thickness of the NA piston because this sounds like a huge CR drop (11.5 down to 8.5). Perhaps someone can do a mathmatical calc based on the cross section bore area and determine the needed reduced dome height.

Years ago I messed with turbo Datsuns and toyotas, on one application we machined the dome for reduced compression height and the piston eventually split across the crown. It was however a cast piston, and by comparison the 3.6 pistons may be forged or cast with different metalurgy.

Another trick with Datsuns was to install shorter rods from another Datsun motor. Is there any possibility that some of the other Porsche rods have a slightly shorter beam and retrofit into the 3.6?

Back in the 80s JE had huge expansion factors but I've read that their metalurgy is far improved since then. I'd be inclined to ask what clearance they spec for the turbo 3.6 bore. For my Datsun race motor they specified 8 thou on a 96mm bore, but again, this was 20 years ago. Not streetable at all.
Old 03-02-2008, 07:33 AM
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