Fenris Ulf

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by kewlbrz:
<strong> </font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Fenris Ulf:
<strong>Then why does a B1 (114 LSA) peak higher than a T1 (112 LSA)? All of the popular hot rodding mags have done dyno shootouts with varying LSAs and the wider LSAs ALWAYS pushed the powerband up higher.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">good question.

i would also ask why do engines built for high rpm extreme conditions have tight LSA's ?</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Thatts easy to answer. As the LSA brings the peak down when it is tightened, the engine builder adds even more duration to the cam to push it back up into the higher powerbands. These kind of cams are way unstreetable with an EFI setup in most cases and are matched with heads that have crazy flow to take advantage of the large durations.

FaSS Blac

Cam Tech is very confusing. All I do know is the MORE duration you use, the higher your power band shifts up also. Me, I like my power band down low, (street car) where it can do ME the most good. How do you think those stock eliminator cars spin up to 7,500-8,000 rpm? They have to keep stock valve lift, but it's open season on duration!!!! Ask one of these guys what their lift is. The'll tell you. Ask them what their duration is. Better have on your track shoes, cause the pipe wrench is gonna be crackin something, and it might be your NUTS!!!!!!!!!! I'm pretty sure though that small LSA's will cause more valve overlap thus creating more over scavenging in the cylinders. This is why factory cams have wide LSA's (114, 115, 117) it reduces overlap which as a side reduces over scavenging and gives us that nice SUV idle Grand Ma loves so much. Does it reduce power? Yes, it does to a certain extent. Intake, intake/exhaust port volume, header size, etc. all play a role in producing the most power. Those hill billys in NASCAR aren't as dumb as some people thought they were, (I'm GUILTY, but now have seen the light). The perfect cam is NOT something the average Joe can obtain. Just realize using a 112 LSA cam in a street car may not let you pass emissions in the Big Hair State (N.J.). I did pass emissions with a '95 LT1 383ci Hot Cam Motor. Don't think I could have without dyno tuning on a 350. The bigger the motor, the more you can get away with as far as rad cams. Ohh, BTW, I was using 1.7 rockers on my 350 LT1 WAYY before the anyone even heard of an LS1!!! Have to watch out for those cylinder pressures though. Broke 5 stock pistons in a stock cammed, ported, shaved head 350 LT1. Turned 12.50 @ 111 mph on a 1.85 '60. Pistons broke because of cylinder pressure spiking. Did you ever wonder why all aftermarket cams.......what the!!!!! It's 4:32PM!!!!!! Atco opens in an hour!!!!!!! Latter dudes!!! <img border="0" alt="[devil]" title="" src="graemlins/gr_devil.gif" />

BigTex

iTrader: (16)

AFTICA..."Your example is generally correct.I would like to know how you calculated the LSA for the 218 cam though.I don't think the calculation is that linear and there are more variables involved."

I was speaking in "general" and did no real calculations, just the understanding that longer durations and the same LSA = more overlap. No doubt that there are many more variables that would go into the equation. We haven't even touched on lobe profiles.

I realize that the LSA is ground into the cam and does not change. By "effective" I was trying to say the the LSA is relative to the duration: a big cam (duration) with a larger LSA has the same overlap ratio as a small cam with a tighter LSA. This is what HP-GURU is getting at too.

LS1derfull

There needs to be mention here that Bill Jenkins is right about his LSA and its effects on power,
BUT that is on a max effort 7500 to 9500 motor with 30 year old design cylinder heads and their in-adequacies taken into consideration. LS1 with medium sized street cams is different. A wide LSA with 224* duration will turn just as many rpm as a 112* but will give up peak power and torque for a trade to have a broader, flatter power curve.
Exhaust back pressure also dictates correct LSA for street car, not a consideration on Hi rpm small blocks of pro stock.Jenkins used overlap to make up for "under valved,low flowing intake ports" of those times(compared to today, not to his competitors of coarse!) <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />

BigTex

iTrader: (16)

Let me throw this thought into the mix:

If the concern over LSA is controlling valve overlap, then does having more valve duration lower the "effective LSA" of the cam? Just the nature of longer duration makes more overlap.

Meaning this -
Say cam A has longer valve events like a 230 / 230 and cam B has shorter events like 218 / 218. Cam A has more overlap than B, making its powerband higher. So even with the same LSA for both cams, the 114 LSA will allow more overlap on the 230 than the 218. That said, the 218 cam would need a 110 LSA to have about the same ratio of overlap to duration as my 230-114 example.

Does that train of thought make any sense?

HP-GURU

Also if you look in the back of the comp cams catalogs, you will see for the same profiles that tightening LSA shortens powerband.

Instead of arguing about this, we need results
on LSA's of 104, 106, 108 on LS1's.

Something like a high lift lobe with 218@.050" and 106 LSA would be interesting.

It would have similar overlap ( or air exchange ) as a 224 on a 114LSA but opens the intake later. Should prove to be a grumpy tq monster that doesn't try to stretch the potential of the long runner intake.

The LSA's have to tighten up eventually on the 346's trying to make huge peak power with the LS6 intake.

HP-GURU

Big Tex I just went there with you.

A shorter duration cam with same overlap as a big duration cam should be as or better driveable than the big duration.

RaNsOm

iTrader: (2)

I understand finally <img border="0" alt="[Fluffy]" title="" src="graemlins/fluffy.gif" /> . Correct me if I'm wrong here.....lets say for instance a 112LSA cam makes peak power at 6500. Then a 114LSA would make power around 61-6300ish...which would explain why a stock LS1 cam with an LSA around 119 I believe makes power in the 5500rpm area. Correct?

FISH 99 WS6

So for example would the TR224/224 114 LSA have a broader powerband and make peak hp at a lower rpm than on a 112 LSA? The 112 LSA would have a narrower powerband and peak a little higher? Is that right?

MelloYellow

I haven't read all the details here, but it looks like the LSA change is important in the way the final CL is done depending on the ground advance.

Maybe it's the lower CL on our 112 cams that moves the powerband down. Typically 106-108 CL on a 112 and a 110-112 CL for a 114.

<small>[ September 28, 2002, 08:02 PM: Message edited by: MelloYellow ]</small>

racer7088

Grumpy as did Smokey both were pioneers in their time but they are also behind the times now and no longer the best. Grumpy would probably take back that LSA comment if you asked him right now.

Pro-Stock and Comp Eliminator stuff can be as high as 120 LSA whereas hobby stocks and bombers as low as 102 LSA. One turns 10,000 rpm and one turns 5500 rpm. Stock production cars have wide LSAs to idle nice and have good emmissions and not because it's good for low rpms at all. You can also ways gain a lot of low end by running a tight LSA and a small duration cam. Duration is still more important than LSA anyday. With really big durations you'd have so much overlap that you need to start spreading the lobes and they always do in general. The better the intake to exhaust ratio usually the tighter you can grind the cam and the worse such as a pro stock or high rpm cylinder head the more you will have to spread the LSA.

AFTICA

iTrader: (8)

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by RedHotZ28:
<strong>I understand finally <img border="0" alt="[Fluffy]" title="" src="graemlins/fluffy.gif" /> . Correct me if I'm wrong here.....lets say for instance a 112LSA cam makes peak power at 6500. Then a 114LSA would make power around 61-6300ish...which would explain why a stock LS1 cam with an LSA around 119 I believe makes power in the 5500rpm area. Correct?</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">I still believe especially after what's been posted in this thread that the wider LSA will move PEAK HP RPM up so then your statement would be backwards.Also I think the stock cams are around a 116 LSA.

AFTICA

iTrader: (8)

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by FISH 99 WS6:
<strong>So for example would the TR224/224 114 LSA have a broader powerband and make peak hp at a lower rpm than on a 112 LSA? The 112 LSA would have a narrower powerband and peak a little higher? Is that right?</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Here again,my opinion is that your statement is backwards.The 114 will have a broader powerband but will make PEAK hp at a HIGHER RPM.

HITMANSS

Thought I'd throw in my two cents worth, just to muddle the waters.

All other cam specs being equal, a wider LSA results in less overlap, while a tighter LSA results in more overlap. Less overlap means better idle, better emissions, and better low RPM torque and throttle response. If the peak HP is also achieved at a higher RPM, then that's the best of both worlds, no?

Well, maybe. The peak HP might occur at a higher RPM, but it may not be as high a HP number as could be achieved with the lower LSA. in general, I think it's clear that the wider LSA results in a broader, flatter TQ curve. That's what important.

This is a great discussion, BTW.

SSLink

I think the bottom line is that a tighter LSA narrows the torque band with higher peak torque. On a street engine spinning 1500 to 6500 this allows the torque to come on stronger, sooner at 2000 RPM up, effectively lowering the powerband. This has been graphically illustrated on graphs I have seen of the B1 vs. T1, with the latter showing slightly better midrange torque. What happens to torque below 2 grand (where we spend little time) or above 6500 is of little consequence to most of us. On an oval track race engine normally turning 7000 to 9000 RPM (NASCAR setups idle at like 2500), a higher LSA spreads the torque band, providing more torque into the lower operating range of the race engine (what happens below 6K doesn't really matter). Thus a street rodder (all about standing start acceleration)and a oval track racer (all about top speed within a narrow power band) might have different perspectives on the effects of LSA. Just my $.02.

JS

iTrader: (4)

I think a 113 LSA might be the best of both worlds depending on valve timing of course.

I'm gonna try advancing my cam to a 109 ICL off its (113ICL) to see what effect it has on ET/MPH.

My cam had no adv ground into it...
Its 113LSA in at 113ICL,But not for long <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />

JS

SSLink

TTT.