Cam Help

[Willys47]

I have been reading up on camshafts and I keep seeing in the specs. Cam Lobe separation (ie 108 or all the way to 114) I can't find a awnser in my books.So what does it do to the operation or output of the engine? please can some one tell me.

[1BAD70CHV406]

A cam with a lower LSA is less streetable and likes more RPM. It will produce more HP and Torque in most cases but is less streetable. anything below 110 is generally not a real good street cam bc they dont like to idle.

[Wild83C10]

Originally Posted by 1BAD70CHV406

A cam with a lower LSA is less streetable and likes more RPM. It will produce more HP and Torque in most cases but is less streetable. anything below 110 is generally not a real good street cam bc they dont like to idle.

Agree.

Narrower LSA have a smaller powerband but will put up bigger peak and average numbers. If you want to read strictly on LSA then pick up the current issue of Chevy High Performance, very good article.
If you are building a street motor then 110 is probably the best LSA, but call a cam manufacture and let them spec a cam for you. Cammotion is pretty much only a custom cam manufacture, great tech guys, you don't have to wait an hour to talk to someone either. The cams are reasonably priced too.

[Willys47]

THANK YOU it's something good to know

[americanmusc1e]

Originally Posted by Wild83C10

Agree.

Narrower LSA have a smaller powerband but will put up bigger peak and average numbers. If you want to read strictly on LSA then pick up the current issue of Chevy High Performance, very good article.
If you are building a street motor then 110 is probably the best LSA, but call a cam manufacture and let them spec a cam for you. Cammotion is pretty much only a custom cam manufacture, great tech guys, you don't have to wait an hour to talk to someone either. The cams are reasonably priced too.

unless you have LS motor they run wide LSA's

[Super73]

LSA = Lobe Seperation. A wider LSA equals less overlap if that is the only thing changed on the cam. More overlap tends to move the TQ band up in RPM making it seem like it has less TQ, but in reality it has pretty much the same it just moves it up in RPM. Since HP is derived from TQ*RPM/5252 moving the TQ up in RPM the motor makes more HP.

Now, a narrow LSA such as a 106 does not make it more or less streetable than a cam with an LSA of 114. It has to do with valve events and total duration of the cam, where you want you power ect.

My first combo in my truck had a 223/228 @ .050 with a 106 intake center and a 106 LSA. I was running LS6 heads on it and I wanted to keep power band's rpm similar to a stock LS6 vette. Even though the cam was bigger duration wise it still peaked at a similar RPM to a stock LS6 cam but made a bit more power through out the curve.

A wider LSA is also typically used with a N20 application as it will open the exhaust valve earlier to reduce pumping losses.

There is a lot to a camshaft, no perfect duration, no perfect ICL or LSA. It's all compramises and a cam should be tailored for your wants.

[Willys47]

So if I have this right a smaller lsa will give you your torque in a short rpm range kind of like a power band.I think got this now cheers

[americanmusc1e]

Originally Posted by Super73

LSA = Lobe Seperation. A wider LSA equals less overlap if that is the only thing changed on the cam. More overlap tends to move the TQ band up in RPM making it seem like it has less TQ, but in reality it has pretty much the same it just moves it up in RPM. Since HP is derived from TQ*RPM/5252 moving the TQ up in RPM the motor makes more HP.

Now, a narrow LSA such as a 106 does not make it more or less streetable than a cam with an LSA of 114. It has to do with valve events and total duration of the cam, where you want you power ect.

My first combo in my truck had a 223/228 @ .050 with a 106 intake center and a 106 LSA. I was running LS6 heads on it and I wanted to keep power band's rpm similar to a stock LS6 vette. Even though the cam was bigger duration wise it still peaked at a similar RPM to a stock LS6 cam but made a bit more power through out the curve.

A wider LSA is also typically used with a N20 application as it will open the exhaust valve earlier to reduce pumping losses.

There is a lot to a camshaft, no perfect duration, no perfect ICL or LSA. It's all compramises and a cam should be tailored for your wants.

you da man

[Super73]

Based on the .050" valve events you listed, I think the cam you are listing is ground on a 112 intake center with a 112 lobe seperation. I don't see 9.5 static netting you 8.5 dynamic. How are you basing your DCR calculations? Off the .050 lift number or the .006 lift number?

In order to get a IVC point of 37.5 ABDC at .006 lift (seat timing which is where DCR is derived from) you would have to have:

211* with an ICL of 112 @ .006
215* with an ICL of 110 @ .006
219* with an ICL of 108 @ .006
223* with an ICL of 106 @ .006
227* with an ICL of 104 @ .006

I'm guessing you are basing you dynamic compression ratio off you .050" lift number and need to be basing it off you .006" lift number. Typical aggressive hyd cams have about 50-60* more duration at .006 than they do at .050. That being said:

A cam with 211* of duration with an ICL of 112 with 50* more duration at the .006" mark would actually equate to 7.7 dynamic compression with 9.5 static. You would have to have 10.5 static to equal 8.5 dynamic.

With a cam having 211* at .050 and 60* more for the .006 number on a 112ICL and a static of 9.5 your dynamic would be 7.4. You would need 10.9 static to equal 8.5 dynamic.


Can you send a link to the MFG's web page with all the cam details?

[Willys47]

I hope you can see this pic this is the formula I use from the book (Max Performace Chevy Rat Motors) it said toal chamber volume = the total swept volx% of cylinder vol divided by the gas type-1 sothe out come of this is to give you the cr that will work best for your cam

[Super73]

The scan is way too small.

How did you figure your DCR based on your cam specs and SCR?

[Willys47]

Originally Posted by Super73

The scan is way too small.

How did you figure your DCR based on your cam specs and SCR?

I was trying to fine the cr that the cam needed to work right now. I need to get the right combo of parts to make it all work. I have never got this detailed about putting a motor together and I want to do this one right and cover all the details.I have been reading all I can and trying to work out all the math.Its realy is a fun learning curve for me, I have never done math for fun untill now!

[Super73]

Typically you want to choose valve events first based on what or how you want the motor to run, then build for max dynamic compression based on the fuel you will run. The fuel is the limit before predetonation becomes an issue. There is more too it than that like head chamber shape, head material, quench ect. But a generic rule of thumb is 8.5 DCR is about the max you can run on pump gas.

With that being said, I was trying to help you work that backwards based on our camshafts intake valve closing point but you only provided .050" numbers not .006" numbers. You are not starting to build compression until the valve is fully closed. Since the intake valve is closing after bottom dead center, the later it closes the less DCR you have.

You are almost always going to make more TQ and HP with more dynamic compression. You mined as well max it out at the 8.5 DCR.

The cam you were looking at going with, can you provide a link to the MFG's page or give us the .006" duration numbers? Then we can work your 8.5-1 DCR backwards and figure out what SCR would be required. Then we can look at the heads you are using, gasket thickness, bore, stroke and figure out what you will need in a piston to achieve your final DCR.