I'm lookin into the comp cam "xtreme energy", and deciding what ones im gona go with. My question is how far can the FACTORY VALVE SPRINGS work out to... will they work at .500 lift, because I know you have to replace them if you are gona run a .550 lift cam. Im proly just gona get a .500 lift cam to avoid PTV contact (it just doesnt sound fun to me if ya know what I mean) Aaaaanyway i will put a pic of the cams I intend on runing, you guys just tell me if I can use the factory valve springs. I appreciate the help.. oh and I am gona be using PI heads.

 

non-pi heads squish the valves .500, pi lift is .550. With stock lift your stock springs are fine but, you should probably spend the 250 bucks for a better set.

Have you decided on which cam? 262? 264? 268? 270? In any case, as far as I know you'll need to do the springs with all of the last 3 in that list.

Enjoy.

EDIT... That'll teach me to look at the pic. Yes you NEED springs. 274 is a hella rough cam. It's probably not the best option for you since your bottom end if stock can't even approach the RPM that allows that cam to build max power.

 

Some good info ^ Sooo basically it comes down to is I will be getting new springs no matter what....well unless I get a really weak cam, but that is kinda outa the question.

so if I have to change the springs, should I look into the .550 lift cams?... the thing I am most worried about is PTV contact.

How far can/should we rev to with a stock bottom end??

 

6k on the stock bottom end is pushing things. 550 lift will probably be ok. I know you can install PI cams in a non-PI motor to get a perf boost. From what I've been told modular motors can stand up to .600 lift without PTV interference but you'll want to check with an engine builder who's got more time inside the 4.6 valvetrain than me. VT engines is a good place to call if you can get someone to answer the phone.

Springs are a definite, you'll need a tune BIGTIME too. It'll run like a sleepy retard till you tune it properly on the dyno and won't be streetable. It's really too much cam for you.

My $.02... The 268 or 270 would be a better choice, they reach peak power at a lower rpm and are much more streetable. Still has a killer idle, and easily winds to 6K but you don't have to get that high in the band to feel the boost. All you're doing is moving the rev limit further out, and moving the power band out to meet it.

At high rpm with capable cams you have less to worry about up top than the possibility of tossing a rod and venting the block.

 

from what I have heard so far
1. it sounds like the .550 lifts are worth it afterall
2. too big of a cam = too big of a problem for my stock bottom
3. I'm getting springs no matter what

did I miss anything... I guess im leaning towards the PI cam with 270/274 adv. dur.
My only other question is why dont they say you need springs in the description of the non-pi cams, and only suggests springs for the PI cams. (Underlined on left in pic) I also attaced the full page so you could see the whole article.

 

I use VT Stage 1 cams with stock valvesprings and see 6500rpm on a regular basis. I pciked up around 20rwhp with these. The comp springs are only marginally better than stock. If you are gonna get aftermarket valve springs get Manley Nextek. This advice was given to me by the best Mod Motor builder in the world (Al Pappito)as far as I am concerned.

 

I am lookin for the hottest cam I can run... so what i'm sayin is stage 1 is not for me. I want something equivalent to vt stage 2's. that is why i think i will end up goin with the 270 cam that pushes out to .550 it has the punch up top that im lookin for... im tired of bein at the track and killin ppl off the line, only to be run down because I dont have the top end to back up my trq.