Cam Guide

III. Internals

Preface:

The LS1 like any other engine works as a system, treat is as one, you want to get as much air in and out as you can. The plethora of mods out there will allow you to do that. Things to consider before you start on your modding process:

1) There is no "best" part when it comes to mods.
2) When you want to start modding your car come up with a tangible plan.
3) Do not go into modding blindly; you will end up wasting money, time, and effort.
4) Do your research before you buy mods.
5) Find out your states/counties emissions requirements before choosing mods
6) Be realistic on what your going to do with your car
7) Usable power under the curve is what you want to shoot for, do not just look at peak gains
8) Work within your budget
9) If your are still under warranty Contact your own dealership and discuss your warranty and modding issues.
10) Work on matching your parts well, meaning:

- do not buy 2500+ stage 3 heads that flow 330cfm@.600 if you have a stock cam or very low duration/lift cam (i.e tr220)
- LSX intake and 90mm TB for a basic bolt on car
- dont run 230+ cams on stock manifolds or shorties
- dont run a big cam and a small stall (i.e tsp231 and a vig 2200)
- dont over/under gear your car (i.e tr230, a4, 2.73's)

(Credit given where applicable. Info/pics taken from personal experience, around the Internet, and ls1tech/ls2.com.) Special thanks to the guys on ls1tech (J-Rod, JMX, ect)


A. Cams

What they are: http://www.ls2.com/boggs/cam/cranecam.jpg

What they do: Cams are the “brain” of your engine and dictate how your engine will perform; power, idle quality, valve events, ect.

What to look for:

- Get a basic understanding of cams before purchasing. It’ll also help you understand the info/advice that is given on the boards.

- ALL gains are relative to your own setup

1) For example if you installed S2 heads and a tsp231 cam and only put down 390rwhp tuned don’t fret if you started with a base of 290rwhp.

- When researching cams look at the average gains. Don’t look at the highest gains you see (395rwhp with say and ls6 cam) and expect to get the same results when the average is 360-380rwhp depending on setup

- Can a cam be your first mod; yes. Should a cam be your first mod; no.

1) Cams need to breath, that means a complete intake and exhaust setup. The bigger the cam the more prevalent those mods become.
2) A4 guys; match your stall and cam appropriately

- Don’t be afraid of older or smaller cams (T1/B1, tr220, comps 218, ect). They might not use the latest and greatest lobe technology or break speed records but they are proven cams and are great for the guys looking for 400 > * rwhp cam only.

- Take Internet reviews of cams with a grain of salt and use them as reference only. Contact your local fbody club or ask around your local regional forum and find as many guys who have cams as you can. Hear and drive/ride along with as many different cam setups as you can. The reason for this is everyone has there own idea of what streetable is since that is a RELATIVE term. Decide on your own what streetable is to you

- Don’t let someone talk you into a cam if it doesn’t meet your requirements and fit your specific applications and goals.

- Keep in mind there is more then one way to make the same amount of power

- If you have the sniffer for emissions either go with the cam of your choice and pray you find a good enough tuner and have luck on your side or keep the duration 226 and under on a 114 and a decent tune and you should be fine.

- When buying a used cam ask for the cam card and/or serial numbers. Take that serial number and email or PM the company or board representative with that serial number. They will be able to tell you if in fact it is one of there grinds and if it’s the one you had planned on purchasing. That is the only way short of having the cam spec’d on a cam doctor to know exactly what cam you are buying. Here's the serial number from my old TR230.

- Don’t get caught up in peak HP. These are ls1 boards not Honda boards . Under the curve power is where it’s at.

- To make things easier most sponsors offer cams as a package deal that includes all that you’ll need for an installation. Here was my old cam kit.




I. Cam Overview:

- http://www.ls2.com/boggs/cam/camanatamy.jpg

- Your starting point:

Stock 98-00 trans am cam

Duration@.050 198.86 intake 209.25 exhaust
Lift .498 intake .497 exhausts
LSA 119.45

Stock 01-02 trans am cam

Duration@.050 196.37 intake 208.72 exhaust
Lift .464 intake .479 exhausts
LSA 115.92


When buying a cam it comes with a cam card. This card gives you the exact specs of the cam. Here is an MTI/Lunati B1 cam card and a LGM G5X2 cam card.


A. Duration:


- The amount of time (in degrees) that lift is generated is called the duration of the lobe. Camshafts operate at half engine speed. This is easy to see because the gear that turns the camshaft is twice the diameter of the crank gear that drives it. That means that the cam spins at half engine speed. Because of this, camshaft duration is always expressed in crankshaft degrees. This makes it easy when it comes time to degree the cam to ensure it is positioned accurately in the engine.

- As you can see in the 2 cam cards there is duration @ .050 and duration @ .006. Duration @.050 is pretty much industry standard and that’s what you’ll see when looking at cam specs from the various sponsors and what most people are talking about when discussing duration

- Duration @.050 and Duration @.006 is a way you can determine the difference between two or more cams with the same given duration at .050. For example a TR224, TSP 224, and Comps 224. The lower the duration @.006 the more aggressive the ramp rate. The more aggressive the ramp rate the more overall and under the curve power.

- If you know the advertised duration (.006) of a cam you can calculate the ramp rate. To do this you take the duration @.006 and subtract it from the duration @ .050. A number of 53 or higher denotes an XE lobe or other mild lobe and a number of 49 or lower denotes an XE-R lobe or other aggressive lobe (Beast and 99 Black Bird T/A )

- Using the B1 and G5X2 as examples is as follows:

B1: 281 (.006) – 221 (.050) = 59

G5X2: Intake 281 (.006) – 232 (.050) = 49
Exhaust 289 (.006) – 240 (0.50) = 49

- Most cam companies use Comp lobes; either an XE or XE-R, the later being the more aggressive of the two. TR uses its own proprietary lobe and FMS uses Cam Motion lobes.

- Intake opening (IO) usually occurs before top dead center (BTDC), while intake closing (IC) happens after bottom dead center (ABDC). For the exhaust side, exhaust opening (EO) occurs before bottom dead center (BBDC) and exhaust closing (EC) after top dead center (ATDC). These data points are listed on the cam card that comes with each new cam.

- Traditional Splits refers to more exhaust duration and lift then intake (tsp231/237, g5x2 232/450, ect). Reverse split refers to more intake duration and lift then exhaust (TR 230/224, X1 230/227). Single patterns are defined as having both the same intake, exhaust duration, and lift. (TR224, TR220, FM4 226/226). Which cam is better depends on your application.

- GREAT technical discussion on cams started by J-Rod from ls1tech: here

- Valve Events (VE) calculator can be found here

- Other good technical **** can be found here and here and here



B. Lift:



- Lift is defined as the difference in height between the radius of the circle and the height of the eccentric. This is called lobe lift.

- When viewing cam specs the lift portion is the gross lift, meaning its calculated with the 1.7 stock rockers.

- To get the lobe lift you take the advertised (gross) lift and divide it by 1.7. If you follow the B1/X2 cam card you’ll see that they list both lobe lift and gross lift.

- If you want to add higher ratio rockers and want to know your new lift you do the following using the B1 as an example:

.559 / 1.7 = ~.329, you then take that lobe lift and multiply it by whatever rocker ratio you want. With SLP 1.85 rockers your new lift specs become .329 X 1.85 = ~ .609

C. Lobe Separation Angle (LSA)



- LSA is defined as spread in camshaft degrees between the intake centerline and the exhaust centerline.

- Overlap is the number of crankshaft degrees that both the intake and exhaust valves are open as the cylinder transitions through the end of the exhaust stroke and into the intake stroke

- LSA is ground into the cam and cannot be changed without grinding a new cam

- Bigger duration cams will have more overlap then a smaller duration cam even if both are on the same LSA.

- The key to making overlap work is maximizing the power in the rpm band where you want it.

- Long overlap periods work best for high-rpm power. For the street, a long overlap period combined with long-duration profiles combine to kill low-speed torque

- Reducing overlap on a long-duration cam will often increase midrange torque at the expense of peak power, but if the average torque improves, that’s probably a change worth making.

- Many enthusiasts purchase a camshaft strictly on the basis of how it sounds. A cam with generous overlap creates that distinctive choppy idle that just sounds cool.

- You’ll find that a 112 or 114 LSA with a 108 and 110 ICL respectively is the best all around street setup.

- While doing my research on the T1 I cam across this dyno in which if I recall Tony (Nineball) stated that the blue graph was a T1 (112 lsa) and the other 2 where a B1 (114) lsa. 112 vs. 114

- What really affects where the cam makes the most power is the intake timing events. What affects drivability most is the exhaust-closing event.


D. Advance and Retard:

- When you see cams specs like 224/224 .563/.563 112+4; the +4 denotes that the cam has 4 degrees of advance ground in.

- Most off the shelf cams have 2 or 4 degrees of advance ground in. This lowers the power band slightly and offers more low end and midrange at the sacrifice of a bit more top end power

- For cams used primarily on the street the advance is best appreciated. For a strip or racing setup 2 or 0 degrees advance will net you more peak power in the upper ranges of the power band

- To find out if you cam has advance ground in you can check on the cam card. Besides the +2, +4, you can determine the number by looking at the intake center line (ICL). Referring back to the B1 cam card you’ll see that it states that those are the specs when installed on a 108 ICL.

- Subtracting the ICL from the LSA will give you the advance: 112 – 108 = 4 using the B1. Or 113 – 109 = 4 using the G5X2.

- Retarding the cam does the opposite of advancing it, it pushes the power band up slightly and gives more top end power.

- With an adjustable timing chain or degreeing the cam you can install the cam at different ICL’s.

- Keep in mind as stated; most cams already have advance ground into them so if you buy an adjustable timing chain and advance 2 degrees you’ll increase the overall advance to 6 degree’s if the cam has 4 degree’s ground in.

- Also with big cams and/or milled heads piston to valve clearances starts becoming an issue. If in doubt always clay the heads and find out your PtV clearance before installing/advancing especially if your cam has a big intake duration as advancing starts the intake valve events sooner.

- Installing dot to dot or degreeing at the said ICL is the best bet.




II. Which cam is right for you


- The key to cam selection is to be brutally truthful when it comes to how you intend to use the engine in question.

- Don’t succumb to the temptation to put the biggest cam you can find into your daily driver.

- If you want to be a lazy **** and not do your own research to find the cam that best suits your application you can just pick up a tr224 114 cam which is the quintessential all around great daily driver cam.

- Pretty much any 220 to 230 duration, .550 to .590, 112 or 114 cam is considered relatively small and great for a daily driver application with the right tune.