pi heads conversion + which cams

chevyboy_z28

New Member

Jan 1, 2004

66

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0

Wixom, MI

Mar 22, 2007

#1

• Mar 22, 2007

• #1

ive got a 98 gt with stock internals and was wondering what options i have as far as cams if i convert to pi heads. I know there are several options for pi headed cars, but in converting to pi heads i raise the compression of my npi motor to 10:1. now with bigger cams in pi heads, on a npi shortblock will i have ptv clearance issues?

basically what im dealing with is this, stock npi shortblock+ patriot stgII heads (ie600 lift springs), + which cams? all the comp cams for pi heads have .550 lift, and the ones i was looking at getting (xe278ah), i was told that i would definately have ptv issues, with having a npi shortblock?

 

stangman

15 Year Member

Jul 10, 2003

2,690

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in a 3 bed, 2 bath

Mar 22, 2007

#2

• Mar 22, 2007

• #2

vt stage 1 cams pretty much anything larger & yu're going to have ot have valve reliefs cut in your pistons

 

CobraM23

Founding Member

Oct 16, 2002

266

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16

Johnson City, TN

Mar 22, 2007

#3

• Mar 22, 2007

• #3

VT stage II NA cams here. No PTV problems either.

 

chevyboy_z28

New Member

Jan 1, 2004

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Wixom, MI

Mar 22, 2007

#4

• Mar 22, 2007

• #4

what kinda gains are to be had with the stock npi heads and a decent set of cams? will the vt stg1s work with npi heads?

 

Skidzz

Tinkerbell

Apr 11, 2005

328

1

19

Salt Lake City, UT

Mar 22, 2007

#5

• Mar 22, 2007

• #5

I've got comp 262's and they are great. No PTV contact and they added around 20 rwhp on top of the gains from the pi swap. But, if you are going to do it, get cam gears with it and have them degreed in for even more gains. That's something I didn't do, and it kept me from hitting my goal of 275 rwhp.

 

Skidzz

Tinkerbell

Apr 11, 2005

328

1

19

Salt Lake City, UT

Mar 22, 2007

#6

• Mar 22, 2007

• #6

chevyboy_z28 said:

what kinda gains are to be had with the stock npi heads and a decent set of cams? will the vt stg1s work with npi heads?

Click to expand...

20-30 rwhp gains, depending on the grind. I don't think VT even makes a cam for NPI's, but comp does. My advice would be not to even change the heads. Get the PI intake and an adaptor, and then get some comp 268's for the NPI heads. You can even buy them from VT's web site for $565 right now, but you might find them cheaper somewhere else. That way, you will still put down probably over 250 rwhp and you will keep the compression low, so you get still run on regular gas and get a blower later on, not to mention you'll save a lot of $$$

 

chevyboy_z28

New Member

Jan 1, 2004

66

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Wixom, MI

Mar 24, 2007

#7

• Mar 24, 2007

• #7

would it be worth it to go with the crower spring kit offered on the vt site, or are the comp srings (best seller list) good enough. ie the crower springs come with retainers, and are allegedly good up to .660 lift. i know thats prolly overkill for me right now, but there only $60 more than the comps?...i know the vt stg1 ones dont require a spring upgrade, but ide rather be safe than sorry (i dont cut corners to save a lil cash)

 

four six

Member

Jan 19, 2006

506

2

18

Hobart, IN

Mar 24, 2007

#8

• Mar 24, 2007

• #8

VT stage 1 or 2

I love the sound of stg 2

 

chevyboy_z28

New Member

Jan 1, 2004

66

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Wixom, MI

Mar 24, 2007

#9

• Mar 24, 2007

• #9

yea i like the sound of the stage2s also, and i think theyd work well with my current mods if i had ported pi's and a strong shortblock.