How important is lobe separation in camshaft selection?

LXSTASY · May 23, 2005

I am in the process of a HCI build-up. I already have AFR 165's (cleaned up on exhaust), ported and gasket matched cobra intake, BBK longtubes (1-5/8), Dr. Gas 2-1/2" X-pipe. I plan on running 24# injectors with a C&L 76 mm mass air.

My question is on camshaft selection. I am looking at the comp cams XE270HR. There are two versions of the cam with different lobe separations. One is 112* and the other is 114*. The specs are 218/224 @.050 and .512/.512 with a 1.6 rocker. From what I vaguely understand is that the lower the l/s (112*) the more power it makes in higher rpm. Conversely the higher the l/s is the beter it will idle. I would like the cam to idle well without headaches, and a chip will come later in time. Would a 114* l/s be a better choice or can I get away with a 112*?

Would the 112* make more power than the 114*?

Dan

90Notch · May 23, 2005

I would use the 112LSA and never look back

Michael Yount · May 23, 2005

You really can't generalize much when it comes to cams -- go here, open every tab and read. You'll see what I mean - it's the valve events that are important. Duration, LSA, etc. just fall out of calculations AFTER valve event timing is determined.

http://www.wighat.com/fcr3/

skip nay · May 23, 2005

106-108
all motor and nothing more and want the most out of that motor

108-112
motor maybe a little less hot or small amounts of nitrious

112-116
motor lazy but you can use lots of nitrious, blower, and/or turbo with alot more boost

Hope this helps you out. Just a simply way of explaining and then you can decide what you need or call a cam place and they could help you more.

90Notch · May 24, 2005

For your parts the 112LSA has less emphasis on the exhaust, which the 165s don't need. It also closes intake earlier and opens exhaust later giving less overlap but still enough to keep idle issues from happening & making more power.

LXSTASY · May 25, 2005

So for the most power with a good idle a 112* would be the best?

90Notch · May 25, 2005

Yes, earlier clsoing intake will make more torque sooner and less overlap will make more power up high. These should equate to more power over a wider rpm range (area under curve). Also, the the tighter LSA (in your setup) is a closer match to what your setup requires. Both cams have both low durations and enough overlap to give you a smooth idle.

nosmatt · May 25, 2005

skip nay said:
106-108
all motor and nothing more and want the most out of that motor

108-112
motor maybe a little less hot or small amounts of nitrious

112-116
motor lazy but you can use lots of nitrious, blower, and/or turbo with alot more boost

Hope this helps you out. Just a simply way of explaining and then you can decide what you need or call a cam place and they could help you more.

REALLY?

LMAO

anyway, michael said it already.......

but, i will ask ya, does your rule of thumb apply to say a 306, with an afr 205 head, and a tfs r intake, that wants to rev to say 6800rpm???

which lsa is perfect now?

now, same combo, but with ported e7 heads????

OHH, AND IS A STOCK 5.0 LAZY DOWN LOW? about the only place it has anything actually.......know what the lsa is on a stock 5.0?

LXSTASY · May 25, 2005

So a 112* will make more power over a wider band and should idle fine b/c the overlap isn't that big?
Correct me if I am wrong anywhere.

SPEED FREAK · May 25, 2005

nosmatt said:
REALLY?

LMAO

anyway, michael said it already.......

but, i will ask ya, does your rule of thumb apply to say a 306, with an afr 205 head, and a tfs r intake, that wants to rev to say 6800rpm???

which lsa is perfect now?

now, same combo, but with ported e7 heads????

OHH, AND IS A STOCK 5.0 LAZY DOWN LOW? about the only place it has anything actually.......know what the lsa is on a stock 5.0?

I'm curious now... What is the LSA on a stock cam? I never cared to look before.

*edit* Ok they seem to range from 116 - 118 ha ha ha.

90Notch · May 26, 2005

"Correct me if I am wrong anywhere."

No correction needed, right on all accounts.

Michael Yount · May 26, 2005

LXSTACY - I guess I see it differently than 90Notch. You simply can't make generalizations of the type that many are making in the thread when it comes to cams. It depends on the particular set up....just not much of a way around that.

90Notch · May 26, 2005

Mods: 3:73's, hurst shifter, mac shorties, bassani x w/cats, flowmasters, underdrive pulley, C&L 76mm MAF, chrome ponies, B springs, subframes, Southside upper C/A's, battle boxes, Aluminum D\S, Nitto drag radials, smoked headlights, 8500k HID's
In process:
AFR 165 58cc Stud Mount
Ported Cobra
Steeda Aero Wing (ordered 5/23)
LT's, Dr. Gas X. Chrome Tails
Black Leather Seats
UPR C/A's and CC Plates
Bumpsteer Kit
+More

I am in the process of a HCI build-up. I already have AFR 165's (cleaned up on exhaust), ported and gasket matched cobra intake, BBK longtubes (1-5/8), Dr. Gas 2-1/2" X-pipe. I plan on running 24# injectors with a C&L 76 mm mass air.

Would the 112* make more power than the 114*?

LXSTACY - I guess I see it differently than 90Notch. You simply can't make generalizations of the type that many are making in the thread when it comes to cams. It depends on the particular set up....just not much of a way around that.

Mike I'm confused, he provided us with his specific setup then asked of two cams which would make more power. What generalizations are being made?

Michael Yount · May 26, 2005

I think you and I just have a difference of opinion about it. No big deal. I can't conclude what would happen with just a change in LSA in his circumstance. I'd want someone like Buddy or Ed to model it and tell me what the impacts of that change might be. Think about it - you can change the LSA - and depending on how that's done, that can impact the intake opening/closing event, the exhaust opening/closing event or both of them. So simply moving to a 112 LSA doesn't dictate how the valve timing will change. And it's the specific valve timing that will tell you how the power and torque characteristics are gonna be affected. LSA is just a calculation that falls out after the timing events are set.

That's why I say it's probably an over-generalization to say that a certain change in LSA will cause certain specific changes in the engine's character.

But -- take it with a grain of salt. Just my perspective.

90Notch · May 26, 2005

"I can't conclude what would happen with just a change in LSA in his circumstance. "

Sure you can, the different LSAs have different vlv events associated with them that are easily determined. Reread my posts and you'll see that my opinion is based on the difference in the intake events, exhaust events and overlap from this cam having a 112 LSA rather than 114LSA. Buddy's chart tells the same story I do.

Aliate X · May 26, 2005

What kinda LSA is in a B-Cam, just to give me an idea of what kinda idle were looking at here with certain LSA's.

SPEED FREAK · May 26, 2005

My understanding was that the comp cams XE series cams have ridiculously quick ramp rates (valves open and shut faster) so in this case I would have to say that the difference in the lsa is more closely related to idle quality than anything else (give up most of the overlap with the 114*) Either cam will work really well I'd assume i have always seen great results with the xe 270... It will be going in my next project.

Michael Yount · May 26, 2005

90Notch said - "Sure you can." And that's where we disagree. You've mistaken your use of pronouns. YOU can. I can't. I don't see your interpretation of the issues the way you do. I'm ok with that.

maverick0716 · May 26, 2005

The stock cam has an LSA of 116

How important is lobe separation in camshaft selection?

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