Cam lift for PI swap

Outlaw97GT · Feb 26, 2009

I got my heads and head changing kit, and my wife bought me the PI intake. So now Im saving up for the cams and LT headers, and vavle job on the heads.

Question is on the cam lift. I have been searching and finding that some say you can use a .550 lift cam and other say you will have PTV problems with anything over .535 lift.

The cams Im debating are...
Patriot cams, .540/.550... If I can use a .550 lift?
Comp 270AH, .550/.550... " "
Comp 268H, the worry free cam

Any opinions?

And before anyone jumps in with the "patriot's are junk" bs, Ive seen their products first hand in Mustangs and F-Bodies... So I know better. And with the price drop to 450.00 for stage 2 cams, I bet alot of ppl will be running them soon.

Thanks

96StangGT · Feb 26, 2009

I currently have the Comp Cams 270s installed and didnt have to change a thing with pistons or nothing it didnt hit the pistons or anything the clearance is fine...and sounds pretty sweet too :headbang:

Outlaw97GT · Feb 26, 2009

Sweet that is what I wanted to hear.... Thanks man!

So how does the car feel now?

96StangGT · Feb 26, 2009

Yea i took a chance b/c i heard the same stuff from ppl saying VTP problems and didnt believe them and i had NO probelms...but yeah it made a difference for sure and i love the choppy idle it gets too, and i have stock headers and non ported n polished heads and it still sounds badass...yeah definately go with a 550 lift for sure...

ccasion14:

glittle75 · Feb 27, 2009

it has nothing to do with max lift on a cam.

NOTHING

its the duration that kills your PTV clearances. when your valves are at max lift, the piston is at least an inch down in the hole.

how long ( Duration) you hold the valves open for is what gets you. PTV issues occur at .100 lift or lower most of the time, becaus the valve is being held open to long, and the piston smacks it before it can close all the way.

im running Comp 274's (Stage 3) in my PI swap, and didnt have any issues. you just need to degree them to make sure the timing is PERFECT.

i thought i had PTV issues with them, but it was just the valvetrain settling, 300 miles into the swap, and she's ready for dyno time.

turned out i was just "overlistening" to the motor during break-in. you'll do it too, when you have work done, every little noise sounds like pots and pans falling

Mr Jones 4.6 · Feb 27, 2009

glittle75 is correct lift does not matter most of the time, what matters is duration. With your stock dish pistons you can pretty much run any cam and be ok just get them timed!!

to give you example when i was building my engine I decided to go with flat top pistons and Comp 262 cams, and when we timed them they clear the piston fine. At the same time we built my motor we also built another motor identical to mine except he was using 268 comp cams and when we went to time them they had PTV issues. So we then replaced the 268s with VT 2s and it timed perfect without PTV issues.

So that just shows that mine and his cams had the same lift but he had more duration and it hit the piston, then when he went to VT2s it has a little less lift and duration was setup different and it worked out. Now I know a guy that is running flat top pistons w/o valve reliefs and he put in 270 comp cams but he timed them as close as he could before it touched the piston, but the thing about is he cannot get the full potential out of the cams. Now whether to say that is would add another 5hp or 15hp if he were able to time it completely thats hard to say.