PI Cam swap suggestions

281cammer · Jun 12, 2008

I actually need 2 cam suggestions

1.- Buddy has a 03 GT wants to do a aggressive(sounding) cam in his GT. He will be doing a blower install shortly. What would be a good recommended cam for his car where he won't have PTV issues.

2.- Here's the trickery one. Another Buddy has a 98 GT PI swapped car. He went to local shop today and they told him that there wasn't any aftermarket cams available for his car that wouldn't give him PTV issues. Which I could understand being Pi swapped cars have 10.1 C/R so the smaller CC lead to PTV issues I'm sure

I greatly appreciate any help received
Steve
__________________

CobraRed_96_GT · Jun 12, 2008

1. He shouldn't be doing cams for the sound, that's kinda sad. But at any rate he should be getting blower cams, stage I or II - all blower cams sounds a little less "lopey" than their equal stage NA cams.

2. That's BS. He can use comp cam xe268H's which are a NPI cam, or comp cam xe262AH's or CMS Stage I N/A cams (what i chose) which are both stage one PI cams. Crower and Crane are also choices. Those in a stage II might even fit just fine when degreed properaly. And it's the piston's dish that's the problem, not the head volume.

Skidzz · Jun 12, 2008

I have a PI swapped '96 with Comp 262AH cams and it runs great. That guy that told you it can't be done is an idiot.

281cammer · Jun 12, 2008

We'll when I say for sound he wants power from them too, he just wanted something with a good lope to it. Like we all do.

Will Smith · Jun 14, 2008

most of these guys hit it right on the money... the NPI cams have a .500 lift and shouldnt be a problem when degreed in. so any choice there should be ok... the PI cams have a .550 lift and u might run into PTV issues with that but maybe a stage 1 like said above when degreed in will work...

just remember what every cam he chooses he need to have the support mods to handle it... YOU CAN "OVER CAM" A CAR

CobraRed_96_GT · Jun 14, 2008

Will Smith said:
most of these guys hit it right on the money... the NPI cams have a .500 lift and shouldnt be a problem when degreed in. so any choice there should be ok... the PI cams have a .550 lift and u might run into PTV issues with that but maybe a stage 1 like said above when degreed in will work...

just remember what every cam he chooses he need to have the support mods to handle it... YOU CAN "OVER CAM" A CAR

+1, i see more threads about people installing stage II/III's with problems or little gains than i see threads of people loving their new cams.

5spd GT · Jun 14, 2008

Will Smith - Peak lift has NOTHING to do with piston to valve clearance.

Will Smith · Jun 14, 2008

5spd GT said:
Will Smith - Peak lift has NOTHING to do with piston to valve clearance.

peak lift, duration, and seperation have everything to do with it...

Ryan441 · Jun 15, 2008

i have a blower cam w/ about 500 miles on it ill sell it pm me

5spd GT · Jun 15, 2008

Will Smith said:
peak lift, duration, and seperation have everything to do with it...

No peak lift has nothing to do with it.

Take a 108* intake centerline, 3.543" stroke, and a factory 5.933 rod.

The piston will be down the bore 2.561", while the valve is open .500"-.600".

So how is that going to hit?

Just for sake of argument let's take a camshaft with .500, or even .600" of peak lift.

Now take the factory 4.6L stroke of 3.543". Why would anyone want to open up the valve all the way (.500"-.600"), when the piston is at TDC?

The pressure differential and volume are next to nill.

Also, do not think one 112* LSA is the same as another 112* LSA (same with duration) and that they will act the same.

So how does one figure out the LSA?

If you know the Intake Centerline (ICL) and the Exhaust Centerline (ECL), you can add them together and divide by 2, as follows:

Say you have a 107 ICL and a 117 ECL.

(107+117)/2 =112 LSA.

Keep in mind, that a LSA of 112 does not mean the camshaft will act the same as another camshaft with a LSA of 112. The LSA is determined by different valve opening and closing events, figuring out the ICL and ECL from them, and doing the above math. I will use two typical camshafts below, to show how you cannot compare a camshaft based on the LSA alone. It is just a little piece in the design of a camshaft.

The Ford Racing Z303 camshaft has the following valve events at .050":

Intake Opening: 7* BTDC
Intake Closing: 41* ABDC
Exhaust Opening: 51* BBDC
Exhaust Closing: 3* BTDC

IO+IC+One Stroke = Duration for Intake @ .050" or 7+41+180 = 228*.

EO+EC+One Stroke = Duration for Exhaust @ .050" or 51-3+180 = 228*.

Now find the ICL and ECL.

Intake Centerline is found by: (Intake Duration/2) - IO BTDC. In other words...

228/2 = 114. 114-7 = 107* ICL.

Exhaust Centerline is found by: Exhaust Duration/2 + EC BTDC. In other words...

228/2 = 114. 114+3 = 117* ECL.

107+117 = 224/2 = 112* LSA.

Now quickly, one can do this for the Lunati 51014 camshaft. It has the following valve timing specs at .050" and a LSA of 112, like the Z303 camshaft:

Intake Opening: 1* BTDC
Intake Closing: 37* ABDC
Exhaust Opening: 49* BBDC
Exhaust Closing: -3* ATDC

Intake Duration is 1+37+180 = 218*. The ICL is (218/2)-1 = 108*.

Exhaust Duration is 49-3+180 = 226*. The ECL is (226/2)+3 = 116*.

LSA = (108+116)/2 = 112* LSA.

Now you see that both, the Z303 and the Lunati camshaft have the same LSA, but different individual valve events and ICL/ECL figures. So how can a camshaft with the same LSA, act the same, or idle at a particular level?

It cannot because of many different factors and an endless amount of possibilities.

CobraRed_96_GT · Jun 15, 2008

Ha. 5spdGT, I knew someone was going to challenge that one. I was ready with a response if so - but not nearly as detailed as that one.

eliteJAE · Jun 16, 2008

5spd GT said:
No peak lift has nothing to do with it.

Take a 108* intake centerline, 3.543" stroke, and a factory 5.933 rod.

The piston will be down the bore 2.561", while the valve is open .500"-.600".

So how is that going to hit?

Just for sake of argument let's take a camshaft with .500, or even .600" of peak lift.

Now take the factory 4.6L stroke of 3.543". Why would anyone want to open up the valve all the way (.500"-.600"), when the piston is at TDC?

The pressure differential and volume are next to nill.

Also, do not think one 112* LSA is the same as another 112* LSA (same with duration) and that they will act the same.

So how does one figure out the LSA?

If you know the Intake Centerline (ICL) and the Exhaust Centerline (ECL), you can add them together and divide by 2, as follows:

Say you have a 107 ICL and a 117 ECL.

(107+117)/2 =112 LSA.

Keep in mind, that a LSA of 112 does not mean the camshaft will act the same as another camshaft with a LSA of 112. The LSA is determined by different valve opening and closing events, figuring out the ICL and ECL from them, and doing the above math. I will use two typical camshafts below, to show how you cannot compare a camshaft based on the LSA alone. It is just a little piece in the design of a camshaft.

The Ford Racing Z303 camshaft has the following valve events at .050":

Intake Opening: 7* BTDC
Intake Closing: 41* ABDC
Exhaust Opening: 51* BBDC
Exhaust Closing: 3* BTDC

IO+IC+One Stroke = Duration for Intake @ .050" or 7+41+180 = 228*.

EO+EC+One Stroke = Duration for Exhaust @ .050" or 51-3+180 = 228*.

Now find the ICL and ECL.

Intake Centerline is found by: (Intake Duration/2) - IO BTDC. In other words...

228/2 = 114. 114-7 = 107* ICL.

Exhaust Centerline is found by: Exhaust Duration/2 + EC BTDC. In other words...

228/2 = 114. 114+3 = 117* ECL.

107+117 = 224/2 = 112* LSA.

Now quickly, one can do this for the Lunati 51014 camshaft. It has the following valve timing specs at .050" and a LSA of 112, like the Z303 camshaft:

Intake Opening: 1* BTDC
Intake Closing: 37* ABDC
Exhaust Opening: 49* BBDC
Exhaust Closing: -3* ATDC

Intake Duration is 1+37+180 = 218*. The ICL is (218/2)-1 = 108*.

Exhaust Duration is 49-3+180 = 226*. The ECL is (226/2)+3 = 116*.

LSA = (108+116)/2 = 112* LSA.

Now you see that both, the Z303 and the Lunati camshaft have the same LSA, but different individual valve events and ICL/ECL figures. So how can a camshaft with the same LSA, act the same, or idle at a particular level?

It cannot because of many different factors and an endless amount of possibilities.

this belongs in a sticky somewhere, very informative

Fastwrx15 · Jun 16, 2008

Stock PI camshafts or Comp XE262.

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