viciousknid

iTrader: (8)

Edited post 4 to show graph that didn't show up.
The paragraph under the graph states the differences.

MikeGyver

iTrader: (5)

That's way different than what I thought. Who do you trust, though: my fake graphs, or ricer's graphs?

budhayes3

iTrader: (19)

Here's my understanding, two cams with the same specs, but LSA being different, LSA will have this affect: The one with the tigher LSA will have a torque curve that peaks earlier and will provide more torque due to increased cylinder pressure. Race cars use a tighter LSA due to more torque being created under the curve from this increased cylinder pressure. An engine with a tighter LSA will have higher peak numbers but a narrower powerband, while a wider LSA will yield a broader powerband, but with lower peak numbers.

I'm sure that we all can agree that a tigheter LSA will provide a choppier idle and lower engine vacuum, with the wider LSA having a smoother idle and more engine vacuum. This is from the increased overlap of the tighter LSA.

BlackGMC

iTrader: (31)

This is just my .02.... I am by no means an expert, this is just what I have read and observed from my two cam swaps on my truck..

Duration and LSA determine the Overlap... Overlap also determines where and how much power the cam will make... A larger (positive) overlap number will make more power up mid/top than a smaller (negative) overlap.... More overlap a cam has a choppier idle, less overlap has a smoother idle.... This example is for the same cubic inches, since larger cubic inches can eat up overlap....

After reading a couple of posts on tech. A good overlap for a LS1 is +6* to give good mix between performance and DD... As cubic inches go up you need more overlap... A good rule of thumb is add 6* of overlap per 50 cubic inches and vice versa... dyno graphs that seem to die off early are IMO from lack of overlap....

Now onto the other part not greatly mentioned when picking out a cam and that is DCR (Dynamic Compression Ratio)... ICL determines how much advance is ground into the cam... ICL = LSA - Advance for example 112+4, 114+4, etc... Advancing the cam will create more Dynamic Compression, Lobe profile also contributes... I have read several articles stating 8.25 is a good number to shoot for a good mix of DD and peformance... Above 8.25, heat becomes a concern due to the compression, good flowing heads help out here.... DCR will determine how much TQ a given camshaft will make, it also determines when it will peak...

So IMO your need to play around with all the numbers to pick a cam best suited for your application...

My next cam will be 220/220 .581/.581 110+3

Search for a post by Piano Prodigy on Tech, he has a great DCR/overlap calculator that has alot of COMPs lobe profiles in it..

sonoma43

iTrader: (1)

That sums it up perfectly!!

chevrolade

iTrader: (22)

Im running a 554' 533' on a 109'lsaIT RUNS GOOD!

viciousknid

iTrader: (8)

Please make graphs for your explanation to some of us that keep getting confused.
OR if you have the money and a dyno. Buy some cams and get us some solid data.

Mangled03gmc

iTrader: (95)

Both BLACKGMC and Budhayes3, somed it up pretty good, about as clear as you can get.. So like I said earlier( only they gave a good description) both have a deciding fact, plays a roll of where and when the power comes in at....

006rcsb

so why is the peaky lower lsa so desireable? The the broad power band that a wider lsa gives seems like it would perform better, especially when you would essentially always be in the power band. Having a torque curve that peaks earlier and provides more torque because of the increased cylinder pressure it doesnt seem like the one peak would outweigh the better power everywhere else the wider lsa would achieve. unless you were keeping the engine at the 5200 rpm where the cams peak is. It seems to me like the difference between a roots and a centrifugal. Roots being a wide lsa and a centrifugal being the low lsa.

Mangled03gmc

iTrader: (95)

Because when you have a converter after your shift, the rpms doesnt drop much like a stock converter does.. I only drop 1500 or so WOT between shifts, so it keeps the engine right where the peaky power of the cam is.. On one that is wider, a stock converter does fine, but having a converter helps still... If your looking for a nice cam that can be DD you want a lower duration wider lsa, unless the advance is ground into it like blackgmc said.. So with that said, having a big converter, low gears, the peaky cams seem to work for the guys thats running them