Will CMS stage 1's work on NPI heads with no upgrades?

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10-11-2008, 03:02 AM

llamatymer

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Will CMS stage 1's work on NPI heads with no upgrades?

Hey guys, i'm wondering if there will be any issues with putting stage 1's in npi heads?

Thanks,

-Matt

10-11-2008, 06:32 AM

lizzyfan

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You must upgrade the springs in the heads

10-11-2008, 12:07 PM

myslow2002gt

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Quote:

Originally Posted by lizzyfan

You must upgrade the springs in the heads

While that's true, you are missing the real issue here.

NPI heads have a .070" shorter valve installed height than PI engines, causing retainer to seal clearance at .540" lift. VT/CMS Stage 1 cams have .550" lift on the exhaust.

In order to run that much lift with a NPI head, he will need .060" offset retainers, or remove the head and have the valve pockets machined.

10-11-2008, 01:02 PM

llamatymer

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Hmm, maybe I'll just wait until I finish porting the PI heads... Out of curiosity where would I get all pf the materials necessary to make them work with NPI because I'm thinking of going FI, and I can't do that with the PI heads because of the higher compression, but if I can stay NPI then I could go with FI.

Thanks a bunch everyone,

-Matt