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Those are RS pistons, designed for 9.5:1 compression up from 8.5:1. They'll give you more room for cams that the stock CIS pistons and with something like S cams, modS cams or maybe GE40 or DC40 cams and carbs or MFI or EFI you'll have a really fun motor. You have the case with a 7R suffix, it's the strongest magnesium case that they made at least for street cars, that's good. The 2.7's are widely known for pulling the head studs out of the case. The case must be Timecerted or case savered in the head stud holes if it hasn't already been done. The 2.7 was the largest street motor built from the magnesium case and it was the first of the smog years so to lower emissions Porsche added a 5 bladed fan which increased operating temperatures and added thermal reactors to the exhaust which increased cylinder and head temperatures, all of which made the cylinders expand a great deal more than the steel head studs, causing them to eventually pull the studs out of the case. Your head studs should also be replaced with either Dilivar, the 993 fully threaded Dilavar, or the Supertec head studs or maybe ARP or Raceware. Head studs are somewhat of a religion and as far as I know religious discussions are specifically prohibited in the rules so I will refrain from stating my beliefs. If you search the engine rebuilding forum you will learn plenty.
You need to buy 2 books. Bruce Anderson's Porsche 911 performance handbook and Wayne Dempsey's book (he owns this place). I got mine used on ebay and amazon for about $13.00 each. Money well spent even if I never built an engine, which I have.
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