Ported or PI Build

97S281 · November 1st, 2010, 01:51 PM

But you have a more friendly CR with ported NPI heads on the stock bottom end than you have with pi heads on an npi shortblock. That makes them more boost friendly than running the p.i. heads on the stock npi shortblock. you can also run a higher lift with a longer duration with the npi's.

The difference in CR in the shortblocks is the dish on the pistons. The long block is different because of the piston's dish and the size of the combustion chambers in the 2 different heads. The motor I am building right now is using a .020+ bore 12cc dish piston with a 54cc head ( svo if ya didn't know ), with a set of matched cometic head gaskets. It's all forged. My CR comes out to be 9.01xxxxx. I will be running 9-11 lbs of boost with custom ground blower cams and a svo blower. Unfortunately, I will have to run a water/meth injection system to keep everything cool because you cannot intercool the svo blower.

lilspanky9119 · November 1st, 2010, 02:12 PM

hmm...Sort of understand, remember I am new to this stuff. I am picking up on most of it though. I do plan on going f/i wayyy down the line so I will be sticking with the NPI heads and hopefully porting them soon. You can also go with more aggresive cams after you port the NPI heads correct?

thanks for all the information

November 1st, 2010, 01:51 PM	#21
97S281 Rollin' 18/ pushin' 2 1997 Saleen S281 Join Date: Feb 2007 Location: The lost highway Posts: 6,673 iTrader: 13 reviews	But you have a more friendly CR with ported NPI heads on the stock bottom end than you have with pi heads on an npi shortblock. That makes them more boost friendly than running the p.i. heads on the stock npi shortblock. you can also run a higher lift with a longer duration with the npi's. The difference in CR in the shortblocks is the dish on the pistons. The long block is different because of the piston's dish and the size of the combustion chambers in the 2 different heads. The motor I am building right now is using a .020+ bore 12cc dish piston with a 54cc head ( svo if ya didn't know ), with a set of matched cometic head gaskets. It's all forged. My CR comes out to be 9.01xxxxx. I will be running 9-11 lbs of boost with custom ground blower cams and a svo blower. Unfortunately, I will have to run a water/meth injection system to keep everything cool because you cannot intercool the svo blower. __________________ MODS IN GARAGE NCMM ORIGINAL BLOWN 96-98 CREW MEMBER # 1 Last edited by 97S281; November 1st, 2010 at 01:53 PM.

November 1st, 2010, 02:12 PM	#22
lilspanky9119 Enthusiast 98 Mustang GT 4.6L v8 Join Date: Jul 2010 Location: 386 FL Posts: 579 Blog Entries: 1 iTrader: 0 reviews	hmm...Sort of understand, remember I am new to this stuff. I am picking up on most of it though. I do plan on going f/i wayyy down the line so I will be sticking with the NPI heads and hopefully porting them soon. You can also go with more aggresive cams after you port the NPI heads correct? thanks for all the information __________________ 3:73 gears, Steed tri-ax, Mac o/r pro chamber mid pipe, w/ 2 chamber 2.5” Flowmasters,C&L upper plenum, Livernois PI intake swap kit, Steeda timing adjuster 16', FR 70mm throttle body, FR aluminum driveshaft, Lowering springs, BBK CAI Last edited by lilspanky9119; November 1st, 2010 at 02:18 PM.

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