RaNsOm

iTrader: (2)

a buddy of mine is selling his GTP cam and I'm thinkin about buying it, he only wants $200 for it, specs are 221/221 .561/.561 on a 114 lsa, but a lot of M6 guys in my club are going with a 112 lsa cam. My question is what advantages come with having a lower lsa?

JackZ28

Power adder cars like a wide angle lobe separation. A wider lobe separation angle will yield less overlap (remember, LSA effects timing events?), which is where the intake valve opens and the exhaust closes.

<small>[ September 26, 2002, 10:26 AM: Message edited by: SSG--Z28 ]</small>

HITMANSS

The 112 LSA cam has more overlap, as the same valve timing events are happening in fewer degrees of rotation. This will make the idle somewhat rougher, and push the power band a little higher.

The 114 LSA cam has less overlap, so the idle will be smoother, and emissions will be slightly lower. The powerband will also be slightly lower.

As was already stated, nitrous & s/c engines benefit from a wider LSA.

770Guy

I went with a 110 lsa on my TR 224/224

Colonel

"The 112 LSA cam has more overlap, as the same valve timing events are happening in fewer degrees of rotation. This will make the idle somewhat rougher, and push the power band a little higher."

You have that backwards about the power band. A narrower LSA will move the power lower. A wider one will move it higher. You are correct about the overlap and the idle though.

Gangly

Uhhhh Hitman SS, I believe you got that backwards. with a 114 LSA, the power band will be higher, on a 112 LSA the powerband will be lower but will have a lumpier idle like you said.

SSLink

For some reason there is still a lot of controversy about the effect of lobe separation on the power band, particularly over on the LS1.com board. My understanding has always been that a tighter (i.e. 112 in this case) LSA increases peak torque and moves the peak and powerband lower and narrower, all other cam specs being equal. Dyno graphs of the T1/B1 bear this out. Although the lower vacuum causes a rougher idle and some bucking right off idle, you come into your peak torque at a lower RPM, due to inreased overlap and higher effective compression. If you can stand (or even like) the lope, this helps, rather than hinders, street performance. PSJ or other valvetrain gurus care to comment? I like a 112 LSA for an M6.

RaNsOm

iTrader: (2)

so in other words, I wont make as much power. All the cammed/headered M6 guys using the TR224 or similar cam have a 112lsa and are shifting around 6400-6500rpm, so in order to make the same power I'd hafta go to say, 6700rpm, haha, which i would have to be crazy to do. So I'd just be shifting around 6.5k but be making a little less power I suppose.

SSLink

Differences in performance between your cam on a 114LSA and one on a 112 with otherwise identical specs would be small. However you will have a smoother idle, slightly lower midrange torque and make roughly the same horsepower at slightly higher RPM. I do agree that you may want more headroom than a 6500 RPM shift to get the most out of a 221 duration 114 LSA cam's powerband, particularly if you run ported heads. I have a 218/218-.563/.563-112LSA and I shift at 6400-6500.

Colonel

SSLink is right on with his ideas.

The best example I can think of is the B1 v/s T1...

B1= 221/221 .558/.558 114 LSA
T1= 221/221 /558/.558 112 LSA

Same cam, different LSA.

Best I recall (Tony, please correct me if I'm off a bit here), the B1 made almost exactly the same peak HP (maybe just a couple of ponies higher which is within dyno variance) as the T1 but did it about 150-200 RPM higher. The T1 had a higher peak TQ by more than a couple of ponies and did it at a lower RPM.

So basically, the T1 would be the better M6 cam where low end power is more of a drivability concern due to lack of a TQ converter. The B1 would be the better A4 cam where idle quality is more of a concern due to the surging/hunting problems that the A4s are more susceptical to.

And really, there isn't THAT much difference between the two but we like to nit pit so... <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

<small>[ September 26, 2002, 04:45 PM: Message edited by: Colonel ]</small>

AFTICA

iTrader: (8)

There sure are a lot of different opinions on what the LSA does to HP, TQ, and at what RPM.

Check out this link from another board;
http://www.ls1.com/forums/showthread...&highlight=lsa

Good points on both sides of that long discussion on LSA, but who's correct?

Colonel

XTROOPER has it backwards. The fact of wider LSAs tending to move the powerband upwards has been well known (and well proven) since way before I was born. Read some of Smokey Yunicks books. <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

AFTICA

iTrader: (8)

Well, I agree with you Colonel, but there sure are alot of people who don't agree with us

JWRENCH

Well I don't claim to be a cam expert but I tried a factory Z28 cam in my 5.3 truck with a 119LSA. It pulled harder from 4500 up but if I held the brake and put the gas to the floor it wouldn't even spin the tires. In other words if it wasen't screeming it wouldn't pull a greasy string out of a dogs ***. So I'd say the higher the LSA the higher the hp peak point. <img border="0" title="" alt="[Roll Eyes]" src="images/icons/rolleyes.gif" />

m1a1

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Colonel:
<strong>XTROOPER has it backwards. The fact of wider LSAs tending to move the powerband upwards has been well known (and well proven) since way before I was born. Read some of Smokey Yunicks books. <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" /> </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">I always thought that increasing overlap would move the powerband upwards. I still don't understand how decreased overlap helps the engine breath at high rpm, but I have accepted it.

I agree with you because I have seen the T1/B1 dyno sheet, but I have a question. Why is it that all the performance cams have smaller LSA's? If you wanted to move the powerband further up (what most people are looking for), why not just increase the LSA? And you get a better idle too!

<small>[ September 26, 2002, 09:23 PM: Message edited by: m1a1 ]</small>

AFTICA

iTrader: (8)

It's hard to disagree with the theory that decreasing the LSA takes the peak power point up, but I will try to explain it as I know it.

What those poeple on LS1.Com are missing is that decreasing the LSA will take the powerband up,but not the PEAK power RPM. It comes on later & stops sooner than a higher LSA,but the average powerband is higher. It's a narrower band of power.The wider the LSA the wider the powerband & the higher the PEAK not AVERAGE powerband will be

Colonel....did I explain that correctly??

98TAauto

iTrader: (2)

ive seen where some guys are making peak power around 6300-6400 with the 114 <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />