Alright, I have read the cam stickies a couple of times now but call me stupid, I still don't quite have a good grasp on relating a cams specs to how it will perform . I understand basically how it works but when I see someone list cam specs in a thread I don't really know exactly what the numbers are telling me. I am going to throw a couple of cam specs out there so that I can be better educated on the difference between them.
As I see it a 220/220-114 is a smaller cam than a 230/236-112 right?, and what effect will having more of a LSA with the same duration have? IE: 224/224-114 compared to a 224/224-112. I just want to be able to know what to look for when I get the money to do my cam. Any help is appreciated. Thanks.

 

a lower LSA will idle choppier and hit the peak HP quicker in the RPM's

 

Okay--I may confuse you, but the two biggest factors of determing how a cam will perform is the Dynamic Compression Ratio (DCR) and Intake Centerline (ICL).

Basically, though, a 224/224 cam is not going to make the same peak power as a 234/234 cam, because the duration is measured at .050" lift and tells us how long the valve is held open. The longer it is held open, the more air that can enter the engine. A wider LSA (numerically higher number) will peak later, offer a better idle, and provide a wider powerband. Lower LSAs do the opposite, producing narrower and more peaky powerbands that usually produce more torque. The LSA tells us how the valve events (VE) will take place. This is where the ICL can affect performance. Still with me?

For example, a 224/224 114 LSA installed at 114 ICL will peak higher in the RPM range than a 224/224 112 LSA installed on a 112 ICL. That usually is good for a small percentage of extra ponies, because the powerband is shifted slightly up and broadened slightly. The difference is the midrange is softer on the 114. That's because a tighter ICL is crucial to upping the DCR (which itself is a derivative of the static compression, or the number you see like 10.1:1 for the LS1). More DCR means more torque, because DCR is basically cylinder pressure for this discussion.

Now, you can have a 224/224 114 LSA cam installed on a 112 ICL, which is usually shown as 114+2 LSA on a website or cam card. This is known as advance. This does the same thing, but gives you slightly different VEs from a 224/224 112+0 (112 ICL and no advance). Advance will widen the exhaust VEs and cause even more cylinder pressure to build.

Now, a 234/234 cam will have a much lower DCR for a given static compression (like 10.1 of the LS1) if the LSA and ICL are the same as the 224/224. That's because a larger cam will "bleed" compression and reduce vacuum due to it having more overlap. Overlap means high RPM power, but more overlap reduces overall drivability (however, a good tune can reduce most of these affects within reason).

If you combine these two we have the following: A 224/224 114+2 cam will peak lower and provide more torque than a 234/234 114+2 cam. The 234/234 will make a lot more peak horsepower and will feel "peaky." But, a 234/234 110+2 cam will provide similar torque (due to similar DCR), and will peak about the same place. But it will make more midrange and topend power of the smaller 224/224 cam, because more air is getting into the engine. But it will make a lower absolute topend number than the same 234/234 on a 114+2. The 114+2 would be a dyno queen and the 110+2 would win the race due to more power in usable RPM range. The 110+2 will also idle a lot rougher and may not clear some aftermarket cylinder heads.

So, if you want just a nice cam for the street, you might look into a 224/228 split with an aggressive lobe like the Comp Cams XE-R or LSK (harder on springs, but provides better fuel economy, drivability, and low end torque) with a 112+2 LSA or 112+4 LSA.

 

Thats a pretty good description, just start reading the cam guide sticky and some of those cam descusion threads and you'll learn a lot. After a few weeks of reading and i was starting to be able to designing my own cam(playing with ve tables). It was really nice to be able to start reading things and understanding them, and be able to know what exactly i was ordering. My new cam that i just ordered today from Thunder Racing is a 228/232 .639/.643 112 +2 both on those LSK lobes. Have to say that Geoff at Thunder is a GREAT guy.

 

Awsome thanks alot for the info guys. Yeah basically with my exhaust the way that it is (very little restriction) and the ram air hood combined with the slp air box, most of my power right now is up at the top of the rpm range. I was thinking that I should find a cam that will build its power mostly in the mid to upper rpms to match what I already have so that they will work well together. I definatley want a nice choppy idle and as much power as I can sqeeze out of my setup(keep in mind that I still only have stock heads right now) but also something that I could drive every day. That being said I can deal with some drivabilty issues, but I also don't want an all out drag only car. Thanks again for the info and any more would be great.

 

if you dont have a ls6 intake i would suggest you get that before a cam install, after that you are set up pretty good for a cam instll. For what you are looking for i would look in the mid to high 220 range.

 

Damn Jake fusion,....thats realy good "stuff" Ive been trying to find out how "big" I can go with a cam and still pass emmisions! (its a left coast thing) Ive done just about everything up to internals and Ive read some interesting things about cam only. Oh, ya I have a LS1 late "99" C-5 what do you think ??

 

should go with the other cam stickys top work

 

Gotta keep Overlap to -6 or lower @.050", i.e. bigger negative number, or 43 or less at .006" for a ballpark estimate. It's hard to say, though, unless your tuner knows how to tune around it and has experience with certain cams. Obviously, having headers or aftermarket cats are a surefire way to fail the visual inspection.

As I've never had to go through it, I'm just repeating what I've heard. So, take it with a grain of salt.

 

Thankyou Sir..........

 

Thanks JakeFusion, your input helped out alot. I was just using the 224 cams for the sake of discussion, I am pretty sure that I want to go with a bigger cam though. I am thinking of going with the reverse split cam from Thunder Racing (230/224 .575/.563), but on what LSA I have not decided yet. On their website there is dyno graph with a car running that cam on a 111 LSA on stock heads, and the only major differences from that car to mine is the LS6 intake,ported TB, and a tune. The powerband for that cam is rated from 2200-6800 RPM. Would changing the LSA to say a 110+2 bring the power band down a little from 6800 to say 6200 or so. I know with a tune I could rev higher than stock, but I don't think I want to be running too much higher than 6200-6400 RPM with the stock bottom end.

 

Lowering the lsa will bring the "peak" power down just a little but would actuly carry the power out further if that makes sense. It won't peak as high but the graph wont drop off as soon. Anyways that cam has been putting down some good numbers and you have a free flowing exhuast to back it up. Give Geoff a call at Thunder and talk to him about what you want, he's a great guy.

Justin

 

Thanks Man.

 

Damn that is alot of lift! What springs are you gonna run with that cam and why the high lift in the first place?

 

Using LSK lobes, thats just the way they are. Anyways i'm running comp 921's shmmed to .050 coil bind. Geoff at thunder said with that they should last just as long as a xe-r cam and rev to 7k all day long (we'll find out).

Justin