cam advice please

[96SCstang]

ok, i have a 96gt of course with the stock npi heads. i have pi cams in now which has a lift of close to .550 i believe. i just purchased some comp cams xe274 camshafts from a member of this site for a really good deal. they have a lift of around .500. my question is i didnt put springs on with the pi cams with a lift of around .550 so i shouldn't need springs for these cams....right? i know that other things play into needing springs like duration and rpms. i dont plan on revving past the stock rpm range so i dont believe this will be an issue and the duration is not anything too extreme. it is quite a bit more than stock but is it enough to do springs? the only reason i am asking is because in the next year or two i plan on doing a fully built bottom end with some trickflow heads and i dont really want to spend the money on springs if not neccassary. plus it will be way easier to swap out the cams. please all you guys that actually know about cams and springs chime in with advise. thank you!! :SNSign:

 

[bnmc98]

Those cams need springs. If you don't plan on going more than stock RPM don't bother putting them in. YOu will lose power at those rpm levels. YOu need deep gears and to rev that thing for any gain on those cams. Remember to degree them. If you really want a cam for your stock heads I have a set of Bullet Racing cams that will fit perfect. They are these, never been run. http://www.modularheadshop.com/Cams.htm#2V_-_STAGE_2_-_NATURALLY_ASPIRATED_
you can PM if interested. no loss in low end and will work with stock springs.

 

[CobraRed_96_GT]

Firstly, PI cams Lift 504"/.531"
As you mentioned, it not all about lift, it's about the slop of the lobe too as in how quickly the cam calls for the valve to be reseated. XE274's are like stage III cams, you're basically going to get a very nice choppy idle and near no gains. You'll lose a good chunk of low rpm torque and gain very little to nothing if you don't rev it out.

Secondly, why did you get a stage III N/A cam for your boosted car? A MUCH milder blower cam will make more power than those N/A cams for you. I bet those cams have a bitch ton of overlap.

If you were N/A and maybe ported NPI's i'd recomend these as even as Stage III's they are made for NPI heads and therefore only lift to .500 for that reason and shouldn't need to rev out of the ball park, but definitely to 6100 or so. Even in that case they should have springs with them.

 

[96SCstang]

yea to be honest i wasn't sure if they were going to be right for what i wanted to do but they were a really good deal and i can sell them for what i paid if not more if need be. i was told by a few guys that they are not bad for FI cars. something about the centerline being good or something lol. i dont know a whole lot about cam specs and i dont pretend to. that is why i ask so you guys wouldn't recommend even putting these in then huh?

 

[96SCstang]

ok...i have a couple more questions then. can you explain these numbers to me. i think i know but i am not sure.

intake: open_7deg. before top dead center
close_48deg. after bottom dead center

exhaust: open_57deg. before bottom dead center
close_2deg. after top dead center

the overlap you talk about is on the exhaust stroke and intake stroke correct. so the exhaust valve and intake valve are open at the same time for a total of 9 deg. of rotation correct? is that too much and if so what is an acceptable amount for a FI car?

and you say i have to rev the hell out these cams to see any gain but the spec. sheet on the cams says the range is 2000-6000 rpm which i what i rev to now, so these would be fine in that respect....right? i am not trying to sound pompus i just want to learn.

also they have a lobe center angle of 114deg. and an intake centerline of 110deg. what does this mean? if you dont want to explain this all please just tell me to buzz off and i'll search elsewhere lol. i know it's alot but i just want to know that these cams are no good before i give up on them. if i have to do springs then so be it. it wont be the end of the world if the cams will help make some more power. i am already at 398 rwhp now and am only looking for aroud 415-420. sorry for the long post gentleman.

 

[CobraRed_96_GT]

Well, 96S - i'll give you two things, you dont have a problem asking questions and you ground them with specs. Give it some time with that attitude and you'll be the one answering these threads.
By my calculations at 236/240 at 114LSA 110ILC would make the schedule 8/48 58/2 which would mean 10 degrees overlap - but that's just my math, if Comp says it's the other schedule then trust that as even left to right side head cams can differ from one another then be averaged.

9-10 degrees is huge. To give you some reference, here are a few comparisons.
Overlap has been known to help on turbo apps, specifically ones with low backpressure as to avoid reversion. The VT stage 1 n/a's in my car right now worked well on Hotmustang's TT set-up - and that's in part because of their 6 degrees of overlap and due to his turbo's being twin 62's which means hardly any backpressure as far as turbo apps go. But turbo's are semi-unique that way, they need the quick exchange of gases up top to help sustain spool while it's worth the consequences elsewhere.
Superchargers a different. Overlap can help a centri, but taken too far and you'll just see a lot of cons and few pros. If 6 degrees is okay for a low pressure turbo, it's likely a bit much for a centri unless it's a serious upper rpm build (maybe 4V heads ect); so 9-10 is out of that realm for sure.

Back to comparisons, my custom blower cams (for my PD blower) have .5 degrees of overlap - which i prefer to build boost early and the un-high rpm requirment for my set-up to make power across the board.
A much more centri-blower friendly cam are VT stage 2.5 blower cams which are known to build boost very nice in the mid-range and help kill it up top for centri's and it has 3.5 degrees of overlap.

I recomend reading this:
Last Call Racing Customer Forums • View topic - Camshafts
Especially the begining and the end part (concerning turbos) for overlap. I intend to add more this week with more 4.6 specific info.

Edit: And it saying 2000-6000 doesnt mean a lot, especially with a supercharger.