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Discussion Starter · #1 ·
Can anyone tell me the difference between the PI and no PI motor???
Is it intake/cam, or exhaust, or a combo of the three???
 

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the physical differences are intake/cams/heads

the differences between the various power levels offered in different vehicles with identical PI engines is mostly attributed to different exhaust systems and more agressive tuning in the EEC
 

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Baby Huey
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Heads,Cam, Intake
 

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The difference is mainly in the intake, the heads and the cams, and different cars have different tunes and exhaust systems.
 

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Different pistons also.
 

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PI inake & PI heads with higher lift lower duration cams, larger ports and valves, 42cc heart shaped combustion chamber, 17cc pistons are the main differences
 

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twin turbo 281 said:
PI inake & PI heads with higher lift lower duration cams, larger ports and valves, 42cc heart shaped combustion chamber, 17cc pistons are the main differences
Cams are the same duration-just more lift.
JL
 

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huh iunno your probally right I had always read the duration was shorter for improved torque?
 

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High-Mileage 4.6L Thrasher
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GreenBird said:
Crower says NPI are 202/207 and PI are 200/209
I checked 4-5 sets of cams out if curiosity's sake when I was degreeing mine last time,and found that all of them were +/- 2-3 degrees of each other on intake and exhaust lobes,with neither NPI or PI being consistently less or more.
I'm taking the stance of them all being the same spec,and the manufacturing tolerances are +/- 2-3 degrees.
JL
 

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Johnny Langton said:
I checked 4-5 sets of cams out if curiosity's sake when I was degreeing mine last time,and found that all of them were +/- 2-3 degrees of each other on intake and exhaust lobes,with neither NPI or PI being consistently less or more.
I'm taking the stance of them all being the same spec,and the manufacturing tolerances are +/- 2-3 degrees.
JL
You still running stock cams to get your 12sec times.

Chris
 

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High-Mileage 4.6L Thrasher
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seawalkersee said:
You still running stock cams to get your 12sec times.

Chris
The car went 12.98 with stock cams.
JL
 
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