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*** Cam Guide ***

Old 05-26-2005, 07:40 PM
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Default *** Cam Guide ***

III. Internals


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.

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

A. Cams

What they are:

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 choose a smog friendly grind. Keep the overlap in check, the more negative overlap @ .050 the easier it will be to pass. Here is Ed's (Ed Vert's) Cali smog sheet from his tr224 114 which has negative 4* overlap @ .050.

- 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:


- Your starting point:

Stock 98-00 trans am cam

[email protected] 198.86 intake 209.25 exhaust
Lift .498 intake .497 exhausts
LSA 119.45

Stock 01-02 trans am cam

[email protected] 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 T1 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 T1 and G5X2 as examples is as follows:

T1: 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. Crane also grinds cams with VHP being one of there biggest supporters.

- 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 discussions on cams started by J-Rod from ls1tech: Discussion I Discussion II Discussion III CFM Requirements by RPM (DenzSS)

    - Valve Events (VE) calculator can be found here (J-Rod)

    - Other good technical ****: Engine Theories (Buddy Rawls) and Static and Dynamic Compression (Pat Kelly) and Valve Timing (Comp Cams)

    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 T1/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 T1 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

    Last edited by jrp; 05-29-2005 at 06:30 PM.
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    Old 05-28-2005, 01:18 AM
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    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.

    - 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 T1 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 T1. 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.

    - Degreeing or installing dot to dot 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 or step up to the FMS FM13

    - "Small, Medium, and Large" are relative terms and always changing with the times. 220 to 230 duration, .550 to .590, 112 or 114 cam is considered good starter cams, again, depending on application.

    - When upgrading from a previous cam make sure the increase in duration is more then a few degree's. For the average joe a swap from a tr224 to a tr230 or a FM13 to an FM14 wont be worth the time and effort to swap. Instread of swapping cams save up some money and invest in a good set of heads.

    - A few of the more popular and latest and greatest cams in no particular order:

    TR224 .563/.563 112 +4
    TR 224 .561/.561 114+4
    Comps 224 .581/.581 112
    TSP 231/237 .598/.595 112+2
    G5X2 232/240 .595/.609 112 or 114+4
    G5X3: specs unreleased but bigger then the X2
    TR Trex 242/248 .608/.612 110+2
    FMS FM4 226/226 .575/.575 112 or 114
    FMS FM 10 228/228 .581/.581 112 or 114
    FMS FM 13 230/232 .591/.585 112 or 114
    02+ LS6 cam 204/218 .551/.547 117.5
    LPE GT2-3 207/220 .578/.581 118.5
    GM HotCam 219/228 .525/.525 112
    TSP 225/225 .589/.589 112
    TSP 233/ 233 .595/.595 112
    MS3 237/242 .603/.609 113+0
    TSP 233/239 .598/.603 113
    FM14 232/234 .600/.600 110, 112, or 114 lsa

    II. Valvetrain

    A. Springs

    - For any cam swap you MUST change out valve springs. The stock springs are only good enough for the stock cam and barely at that.

    - As far as springs go you have a few but not limited to the following choices:

    1. Comp 918’s: A few years back they had some problems with non-blue stripe springs breaking but they have rectified the problem. The beehive design is also a superior setup due to there light weight and harmonics.. Your stock steel retainers can be reused with the 918’s but titanium retainers are recommended for lightening up the valvetrain and for strength.

    Outside Diameter (O.D.): 1.290"/1.060"
    Inside Diameter (I.D.): .885"/.656"
    Installed Pressure: 130 lbs @ 1.800"
    Open Pressure: 318 lbs @ 1.200''
    Coil Bind: 1.085"
    Maximum Lift: 0.625"
    Rate (lbs/in): 313 lbs/in

    2. Manley Nextek: Also a single spring like the 918’s but not of the beehive variety. They are a good spring and come in a package deal from SDPC for $214 and that includes titanium retainers. The springs are rated for up to .600 lift.

    Max Valve Lift : .600"
    O.D. : 1.255"
    I.D. : .830
    Installed Pressure : [email protected]"
    Open Pressure : [email protected]"
    Coil Bind : 1.100"

    3. Crane Duals: A dual spring setup rated for up to .650 lift. When buying duals you’ll need the dual springs (obviously), titanium retainers, new dual spring seats, and new valve stem seals.

    Outer Diameter Outer Spring 1.275
    Outer Diameter Inner Spring .937
    Inner Diameter Inner Spring .667
    Damper No
    Seat Pressure @ Installed Height 112 lbs @ 1.800
    Open Pressure and Height 352 @ 1.150
    Coil Bind 1.045
    Maximum Net Lift w/.060" Clearance .650
    Average Spring Rate (lbs./in.) 352


    4. Comp 921’s: Also a dual spring like the Cranes above and come as a kit with everything you need for installation, rated for up to .650 lift

    O.D: 1.300
    I.D: .870 (outer spring)
    I.D: .655 (inner spring)
    135 LBS @ 1.770
    400 LBS @ 1.220
    COIL BIND @ 1.040
    MAX LIFT .650

    5. Patriot Gold Duals: See Crane and 921’s. The PP Golds come on all PP heads. PP are the only genIII spring setup to use the super 7 10* locks.

    O.D 1.29
    135lbs @ 1.800
    385lbs open
    coil bind @ 1.08
    .650 lift

    My Personal Indepedently tested PP golds:

    seat: 143 lbs @ 1.800
    open: 363 @ 1.200
    coil bind: 1.060
    Clearance: .140
    spring rate: 367

    6. PRC Dual Spring Kit: Kit comes with Dual springs, tit. retainers (using stock locks), seats, valve stem seals. good for up to .660 lift

    seat : 140lbs
    open: 390lbs
    install : 1.800
    coil bind: 1.07
    1.290 O.D.
    max lift : .660
    matl : super pure chrome silicone

    - PRC Platinum springs:

    seat: 145# @ 1.7850"
    open: 395# @ ?

      7. Comp 977's: dual spring (requires machining of spring pockets)

      O.D: 1.46
      I.D: .700
      seat pressure: 155 @ 1.850
      open presure: 419 @ 1.250
      coil bind: 1.195
      spring rate: 441

      8. Comp 978's: Dual springs (requires machining of spring pockets)

      O.D: 1.46
      I.D: .697
      seat pressure: 126 @ 1.850
      open presure: 368 @ 1.250
      coil bind: 1.195
      spring rate: 403

      9. Comp 987's: Dual Springs (require maching of spring pockets)

      O.D: 1.430
      I.D: .697
      seat pressure: 121 @ 1.800
      open presure: 388 @ 1.200
      coil bind: 1.150
      spring rate: 344

      10. 01 LS6 springs: max lift .540

      seat pressure: 90 @ 1.800
      open pressure 260 @ ?

      11. 02 LS6 springs or green: max lift ~.580

      seat pressure: 90 @ 1.800
      open pressure: 294 @ ?

      12. 03+ LS6 springs(orange): max lift ~.580

      seat pressure: 90 @ 1.800
      open pressure: 294 @ ?

      13. Stock Ls1 Springs

      seat pressure: 75 @ 1.800
      open pressure: 230 @ ?

      Last edited by jrp; 10-12-2005 at 10:03 PM.
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      Valve Springs: Frequently asked questions

      from CraneCams website

      What is Valve Spring Installed Height?

      Installed height (also called assembled height) is the dimension measured from the bottom of the outer edge of the valve spring retainer where the outer valve spring locates, to the spring pocket in the cylinder head, when the valve is closed.

      How does installed Height affect spring tension?

      Installed height is the determining factor of what the valve spring "closed tension" or "seat pressure" will be. The camshaft specification card, and the spring section of the catalog both show what the approximate tension a particular valve spring will exert if installed at a specific height.

      For example, spring part number 99848 shows 114 lbs. @ 1.700". This means that if this spring is installed at a height of 1.700" it should exert 114 lbs. of tension with the valve closed. (Note: Spring tensions often vary measurably within the same production runs; therefore, it is recommended that each spring be tested on an accurate spring tester and the spring installed at the recommended seat pressure.)

      How do you change installed height and what effect does it have?

      The easiest way to shorten installed height is to insert a shim in the spring pocket below the valve spring. Another is to use a different design valve spring retainer. Retainers with a deeper dish will have more installed height, with a shallower dish, less installed height. You can also use a valve lock designed to change the location where the retainer is positioned on the valve stem. We sell heavy-duty, machined valve locks in std. height and also +.050 and -.050 heights to fine tune your installation. Longer length valves can be used to increase installed height.

      The shorter the installed height (the more the spring is compressed), the higher the valve spring seat pressure will be, and the less distance the spring can travel before the spring reaches coil bind.

      The taller the installed height, the lower the valve spring seat pressure will be, and the further the spring can travel before coil bind occurs.

      (Note: Eliminating coil bind by installing the spring at a taller installed height is not a desirable option. The resulting reduced seat pressure will lead to a significant loss in performance and could also result in engine damage caused by the valve bouncing on the valve seat due to the reduced seat pressure. The best procedure is to select a spring that provides the desired seat pressure at the installed height on the head.)

      What is the importance of valve spring seat pressure?

      Adequate seat pressure is necessary to:

      1) Insure tight contact between the valve face and the valve seat to seal the combustion chamber and provide proper heat transfer from the valve to the cylinder head.

      2) Keep the valve from bouncing on its return to the seat. If the valve bounces, cylinder pressure (power) is lost. Repeated bouncing of the valve is like a hammering action that can result in the head of the valve deforming ("tuliping") or actually breaking from the valve stem resulting in catastrophic engine failure.

      3) With a hydraulic cam the valve spring must exert enough pressure against the valve lifter (or lash adjuster) plunger to keep it centered in its travel to prevent "lifter pump-up". When pump-up occurs the valve is held slightly off its seat resulting in a significant loss of power and possibly a misfire. It is this loss of power and misfire that is often misdiagnosed as a fuel system or ignition system problem.

      High oil pressures and high viscosity oils aggravate "lifter pump-up" in hydraulic lifters. When either oil pressure or oil viscosity is going to be increased beyond the manufacturer's recommendation, a corresponding increase in spring seat pressure is necessary to prevent "pump-up" (even with an "anti-pump-up" lifter). Since oil viscosity in no way relates to the oil's film strength, and the scuffing protection provided by the film strength, Crane Cams recommends following the OE manufacturer's recommendation with respect to engine oil.

      Common Misconception:

      Many people mistakenly think that using higher seat pressures causes a reduction in the horsepower delivered to the flywheel because higher seat pressures (and also higher spring rates required for high performance) require horsepower to compress the springs. This thinking is simply incomplete! For every valve that is opening and its valve spring being compressed, another valve is closing and its valve spring is expanding. This expansion returns the energy to the valve train and the engine. This results in a net power loss of "0" hp. Many engineering texts refer to this as the "regenerative characteristic" of the valve train. Recent tests at Crane have shown no horsepower loss on a hydraulic roller equipped engine when changing the seat pressure from 135# to 165#. Power actually improved significantly at top end, probably due to better control of the relatively heavy valves in the engine.

      In Summary:

      Always run enough seat pressure to control the valve action as it returns to the seat. Heavier valves require more seat pressure. Strong, lightweight valves require less seat pressure. When in doubt, run slightly more seat pressure . . . not less.

      What is Valve Spring Open Pressure and Why is it Important?

      Open pressure is the pressure against the retainer when the valve is at its maximum open point. Adequate open pressure is necessary to control the valve lifter as it first accelerates up the opening flank of the cam lobe and then quickly decelerates to pass over the nose of the cam which causes the valve to change direction. Inadequate open pressure will allow the lifter to "loft" or "jump" over the nose of the cam (referred to as "valve train separation", or "valve float"). When the lifter strikes the closing flank with a severe impact, camshaft life is drastically shortened.

      Open pressure is a function of seat pressure, net valve lift, and spring rate. It must be sufficient to control the valve action at the highest expected engine speed without being excessive. Excessive open pressure aggravates pushrod flexing which in itself aggravates "lofting" of the valve and valve train separation. Selecting a spring to give the proper open pressure, while minimizing pushrod flexing, provides many opportunities for developing a unique, horsepower-enhancing combination. Obviously, lightweight valves require lower open pressures and tend to reduce pushrod flexing and valve train separation.

      One final point: Excessive valve spring open pressure will result in reduced camshaft and lifter life.

      What is a Valve Spring Coil Bind and how does it relate to spring travel and valve lift?

      When the valve spring is compressed until its coils touch one another and can travel no further, it is said to be in coil bind. The catalog shows the approximate coil bind height for the various Crane Cams valve springs. To measure this you must install the retainer in the valve spring, then compress the spring until it coil binds. Now measure from the bottom side of the retainer to the bottom of the spring. This measurement is the coil bind height. This can be done on the cylinder head with a spring compression tool (part number 99417-1), in a bench vise, or in a professional valve spring tester.

      Using the above figure, subtract the coil bind height "B" from the valve spring installed height "A". The difference "C" is the maximum spring travel. The spring travel must always be at least .060" greater than the full lift of the valve. This safety margin of .060" (or more) is necessary to avoid the dangers of coil bind and over-stressing the spring.

      If coil bind occurs, the resulting mechanical interference will severely damage the camshaft and valve train components.

      How do you increase spring travel?

      The valve spring must have sufficient travel (plus .060" safety margin) to accommodate the amount of valve lift created by the camshaft and/or an increase in rocker arm ratio. To increase spring travel you can either raise the installed height (but this will lessen the spring tension), or change to a spring with additional travel. If there is not a standard diameter spring available with enough travel, the cylinder heads will have to be machined and a larger outside diameter (O.D.) spring installed.

      Crane Cams offers some special valve springs in standard diameters which eliminates having to machine the cylinder heads. For example, a small block Chevrolet engine can use spring kit part number 11309-1 to handle .550" to .600" valve lift. The 85-00 302 Ford hydraulic roller engines can use spring kit part number 44308-1 to handle .550" lift.

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      *continued from Crane website*

      Besides coil bind, what other types of mechanical interference should you look for?

      When you increase the valve lift with a bigger cam or increased rocker arm ratio, you must be sure there is no interference between any of the moving parts. Some of the components that must be inspected for clearance are:

      1) The distance from the bottom of the valve spring retainer and the top of the valve stem guide, or the top of the valve stem seal, must be equal to the net valve lift of the valve, plus at least .060" more for clearance.

      2) When using rocker arms mounted on a stud, the length of the slot in the rocker arm body must be inspected to be sure it is long enough to avoid binding on the stud. The ends of the slot must be at least .060" away from the stud when the rocker is at full valve lift and when the valve is closed. Be especially careful when using stock Chevy stamped steel rockers and any high performance stock or aftermarket cam. These rockers will typically not provide enough clearance at full-lift, and will bind on the rocker stud.

      Crane Cams offers long slot and extra long slot steel rocker arms to relieve this interference problem. Aluminum roller rocker arms may be required to provide sufficient travel on larger lift camshafts or when using longer ratio rockers.

      3) The underside of the rocker arm body cannot touch the valve spring retainer. You will need at least .040" clearance to the retainer throughout the full movement of the rocker arm. If necessary, a different shape retainer or rocker arm design will be required. In some cases, installing a lash cap on the tip of the valve stem can provide the clearance required.

      4) Valve to piston clearance must be checked to be sure there is sufficient clearance. The intake valve must have at least .100" clearance to the piston and at least .120" clearance on the exhaust valve.

      What is the critical point of crank rotation for checking valve to piston clearance?

      The critical point for both valves is the "Overlap Period" as the exhaust cycle is ending and the intake cycle is beginning. You must start checking the clearance before and continue after T.D.C. on both the intake and exhaust valves to be sure you have the correct readings through the overlap period.

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      B. Pushrods

      What they are:

      What they do: transfer the motion of the cam to the rockers

      What to look for:

      - New pushrods aren’t absolutely necessary but they are highly recommended.

      - The pushrod was never designed to be a fusible link in the valvetrain. Several years ago we even had a member (might have been in the old days) that was an engineer from Jesel (don't recall his ID) and he was adamantly opposed to the notion that the LS1 pushrods were designed to break in the event of a mechanical over-rev. The job of the pushrod is to accurately transmit the motion of the cam lobe (via the rocker arm) to the valve. If it’s flexing under load, then its simply not doing its job.

      Look at it this way; you CAN mechanically over-rev any engine - pushrod, OHC, rotary, or otherwise - and cause damage. There is nothing unique or special about the LS1 pushrods making them fusible.

      This is like saying that you broke your ring gear on a missed shift so therefore everybody should continue using the weak 10-bolt rear ends. Just a silly, backwards argument IMO - especially when you're considered an aggressive cam with heavier valve springs (Fulton 1)

      - Pushrod Calculator here

      How To Verify Proper Valve Train Geometry


      The following is a method of verifying proper valve train geometry. After you have estimated the required pushrod length using a Pushrod Length Checker, use this method to verify that the valve train geometry is correct (using the rockers you are using in your engine):

      The first step is to install a solid lifter and an adjustable pushrod. Mark the tip of the valve with a marker

      Install your rocker arm and set it up with zero lash.

      Rotate the crankshaft clockwise several times. Remove the rocker arm. The contact pattern of the rocker tip will be where the marker has been wiped away from the valve tip. The pattern should be centered on the valve tip, and as narrow as possible. If it is not, experiment with varying the pushrod length to yield the best pattern.

      Pushrod Too Long: Notice how the pattern is wide, and shifted to the exhaust side of the valve tip.

      Pushrod Too Short: Notice how the pattern is wide, and shifted to the intake side of the valve tip.

      Pushrod Length Correct: Notice how the pattern is narrow and is centered on the valve tip.

      C. Rockers

      What they are: HS 1 / 2, Comp Magnums, Comp Shaft, Crane, SLP 1.85

      What they do: transfer the cam motion along from the pushrods and accentuate the valves to open

      What to look for:

      - New rockers are also an optional choice during a cam install.

      - The stock roller tip rockers have been known to loose there bearings but it’s not an overly common occurrence.

      - One problem people have experienced with the HS and YT rockers are valvetrain issues at high RPM's due to the added weight of the rockers, coupled with heavy dual springs with undesirable harmonics.

      A good alternative is to run the stock rockers retro-fitted by Nasty Nate. They are stock rockers which keep the weight down but the trunion bearings have new C-clips which prevent the needle bearings from spilling.

      - Adjustable rockers allow you to adjust lifter pre-load; a must for Comp R's (875's)

      - Higher ratio rockers can be used to increase lift (see cam lift for more info). Along with increasing the valve lift adding higher ratio rockers also nets you an extra degree or two of duration at the valve and increased overlap.

      - Jesel SS Shaft Mount: INSTALL GUIDE

      D. Others

      - It’s a good idea to install a new timing chain as well. The stock ones are notorious for having a lot of slack in them
      - You can either get a single (JWIS) or double (my rollmaster)
        - The double chains come with the needed spacers to clear the oil pump
        - 98-00 cars should also factor in a new oil pump
        - A new chain and oil pump should run you about 200 dollars


        - JMX is the muthafuckin man, that’s all you need to know
        - Install Guide

        - I along with countless others have followed that guide for cam installs (among other things). If you can turn a wrentch, have some basic knowledge, and follow that guide you can do your own cam install.

        IV. Tuning

        - Factor in tuning from the get go. If you cant afford tuning then just hold off on the install until you can. Its not going to kill you to wait a bit to save up the 350-500 for the dyno tuning.

        1) This is especially true when installing big cams, the bigger the cam the harder it is for the stock PCM to compensate.
        2) Smaller cams can get away with stock tuning longer then bigger cams but even so all cams can benefit from tuning
        4) Tuning is more then just looking for more HP. It makes your car more livable and drivable by dialing in your a/f ratio, deleting codes, helping with hot and cold starts, getting your idle set straight, ect.

        - Of course if you have your own copy of hptuner/flashscan/editor/predator you can do the tuning yourself.

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        Cam Glossary

        asymmetrical: one cam lobe with differing opening and closing ramp rates; it projects different images on either side of the lobe centerline; many modern cam grinds have asymmetrical lobe patterns, often with high opening rates using roller lifters, which allow their use

        base circle (heel): lowest point of the cam lobe in relation to lift; the closed valve position occurs as this portion of the cam lobe turns against the lifter. All valve lash settings are made when each lobe has the base circle (or “heel”) against the lifter (or lash pad on some OHC engines). When a camshaft is being ground, the base circle is the actual part of the lobe that is ground to form lift at the lobe

        basic rpm: the rpm range in which the engine makes the best power

        cam centerline: cam phasing in relation to the crankshaft; where the centerline of the intake or exhaust lobe is in relation to the No. 1 cylinder’s piston given in degrees of crank rotation after TDC. When degreeing a cam, you must know this figure to install it properly. When you do advance or retard the cam centerline (when degreeing a cam), you affect both intake and exhaust lobes; these are not individually adjustable

        degreeing a cam: setting the camshaft’s phase (or position) in the engine in relation to crank position. Most cams today are ground with some advance to make up for timing chain stretch, around 4 degrees. If the installer places the cam ahead in relation to crank/piston timing, it has been advanced; if it’s moved back from straight up, it’s been retarded. Many people used to install a cam advanced, but since most are already ground slightly advanced, there’s usually no need. Always follow the manufacturer’s installation card or instructions carefully

        duration: time (in degrees of crankshaft rotation) that the valve is open during its tappet lift; given in “advertised duration” and at 0.050-inch tappet lift; when comparing cam specs, always compare duration figures at 0.050-inch lift because cam companies measure advertised duration differently

        hydraulic cam: a cam using lifters that has a valve-controlled plunger inside its body, preloading the pushrod at the closed valve position through oil pressure lift: distance the valve is depressed from its seat when closed to the peak valve lift when open fully

        lobe separation: actual spacing of cam lobe centerlines (in degrees) for a common cylinder; ground into camshaft—not changeable; largely responsible for the idle quality of an engine; narrow separation angles seal a cylinder for a longer period of time but also give a rough idle quality, while larger angles generally give a smoother idle in street engines

        mechanical (solid) cam: a cam using lifters with only a radiused contact face in which the pushrod end sits without internal valves or other complexity; requires periodic lash setting

        nose: full-lift portion of the cam lobe where the lifter is pushed open at maximum distance

        ramps: portions of the cam lobes that lift or settle the lifter from the base circle of the cam; does not include the nose. They have different rates of lift in velocity and degrees of crank rotation. Symmetrical cams have individual lobes with the same opening and closing ramp rates, while asymmetrical cams have different opening and closing rates on the same lobe. Roller cams can use more radical ramp rates because of the nature of the roller lifter

        roller cam: in either hydraulic or solid versions, these cams use lifters that employ wheels to contact the camshaft lobes, fixed in needle bearings; these cams often have higher valve opening rates than flat-faced cams and exhibit less friction; most roller cams require using a bronze distributor drive gear due to metallurgical differences in flat-faced and roller cam material, though some new ones do not. Rollers have been widely used in diesel and motorcycle engines previous to automotive gasoline engines

        split duration (dual pattern): cams with intake and exhaust lobes of different specs

        symmetrical: both sides of one cam lobe are mirror images of each other; they have the same ramp rates upon opening the valve and closing it; split evenly on either side of the individual cam lobe centerline

        - CHP

        Last edited by jrp; 05-28-2005 at 05:45 AM.
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        Cam Chart

        click here for bigger image.

        Last edited by jrp; 05-28-2005 at 05:46 AM.
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        Cam Cards

        98 - 00 Stock cam 1 2 3

        MTI T1 (discontinued)

        MTI C1 "Hammer" cam (discontinued)

        Hot Cam 1 2 3

        TR 230

        TSP 231/237


        LGM G5X2

        MTI Y1

        TR Trex

        TR 248

        Comp Cams LSK lobes
        Lobe#, Dur. @ .006", .050", .200", & Lift @ 1.7

        2124 265 215 142 .629
        2125 269 219 145 .632
        2126 273 223 149 .636
        2127 277 227 153 .639
        2128 281 231 156 .643"
        2129 285 235 160 .646"
        2130 289 239 164 .649"
        2131 293 243 168 .653"
        2132 297 247 171 .656"
        2133 301 251 175 .660"
        2134 305 255 179 .663"
        2135 309 259 183 .663"
        2136 313 263 186 .663

        Last edited by Ragtop 99; 12-25-2006 at 03:44 PM.
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        Old 05-28-2005, 04:32 AM
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        Comp Cam lobes XE and XE-R

        Crane Cam Lobes

        Last edited by jrp; 05-28-2005 at 05:47 AM.
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        Old 05-28-2005, 04:55 AM
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        How To: Properly Install And Degree An LS1 Cam And Timing Set

        By Brian Reese (GMHTP)

        It's not your good 'ol small-block, so pay attention. Setting up a new bump stick in Gen III and IV engines requires the same base tools we're familiar with and a few new tools too. We've all read the overly familiar cam degreeing stories, but they all use the same SBC photos that have been floating around for years. GMHTP readers require and deserve a modern story.

        Comp Cams sells a few different style degreeing kits, varying to suit each need and budget. For the pros, engine shops, and guys who seek bragging rights, look no further than Comp's Pro Degree Wheel kit. Each component is available a la Carte as well. If your budget is tighter than a writer's, Comp's Sportsman setup is for you--we'll cover that later. If you're prepared to degree a cam, you'll need a quality timing set too. SLP's latest double row adjustable timing set, PN 55000, is perfect for any performance build. You can still find offset bushings and low-cost timing chains if you're building a real budget engine.

        Cleanliness is the key to any internal engine work. Even brand new parts must be washed and cleaned. This is the right time to visually inspect your parts and confirm you received what you ordered. Once your engine is prepped and the parts are cleaned, the cam lobes and journals must be liberally coated with an ultra slick and ultra sticky lube. We use Permatex Ultra Slick, available at any auto supply shop. Pop for the good stuff as plain engine oil won't cut it. Cover all the lobes except the number one cylinder intake--this lobe gets coated after the degreeing is finished. The lube is cheap insurance, and can't hurt anything, so load up.

        Guiding the cam into the block is a little easier said than done. An extension tool is recommended to provide an adequate handling point. If you're only doing one cam install, you can get by using some longer bolts screwed into the snout of the cam. Installation requires precision, so be careful not to nick any cam bearings or **** the cam sideways during the install. Be patient.

        On Gen III and IV engines, the cam is held in place with a four-bolt plate. Make sure the integral gasket is clean and intact prior to installing.

        SLP's double row adjustable timing chain and sprocket set includes everything shown. The aluminum spacers provide clearance for a factory oil pump. SLP also sells a performance oil pump that does not require the spacers, PN 55001. SLP's crank sprocket and oil pump drive cog are two separate parts, making for an easier install. A precision needle bearing is provided for the backside of the cam sprocket

        The cam timing is adjusted by phasing the crank's sprocket on different crank keyways. Each keyway is marked in degrees of cam advance or retard. Options on the sprocket include -6, -4, -2, 0, +2, +4, +6. The sprocket is installed with the keyway matching the label of the desired advance or retard (advance is positive, retard is negative). Once installed, the cam sprocket alignment dot must be aligned with the corresponding sprocket tooth. Do not attempt to line up the keyway with the cam sprocket. In the photo, a pointer is marking the 0 keyway, and the finger is touching the correspondingly marked 0 sprocket tooth.

        Here's the proper position of the crank sprocket relative to the cam sprocket, for 0 degrees of advance. Camshafts are typically advanced for increased low-end torque and retarded for higher horsepower. Without the luxury of dynamic cam phasers on Gen III and IV (yet), you'll need to pick one over the other! Adjustable timing changes do allow for future adjustments, however.

        Alignment of the cam sprocket dot and the selected sprocket tooth is critical. A small straightedge can be used to check alignment. Double check alignment before moving on.

        A degree wheel effectively creates a physical crankshaft position meter. The resolution of the meter is proportional to the diameter of the wheel. Larger diameter wheels offer higher resolution. Comp's pro wheel is an attractive part made from anodized aluminum and sports CNC'd labels. This baby will last a lifetime. The wheel is attached using the supplied bushing and an old balance bolt.

        To use the Comp indicator base on the Gen III and IV engine, you will need a 5-inch long piece of 3/4-inch (outside diameter) tubing and an old head bolt. The tube is bolted to the block and is used to support the indicator base fixture jig.

        The first step to degreeing the camshaft is to locate the crankshaft's exact position (referred to as crank or rotation angle) when the number 1 cylinder is at top dead center (TDC). There are many effective means to find TDC. The first step with the dial indicator is to align and square the indicator tip with the center of the piston. Next, the crank is rotated until the piston is at TDC, as best we can tell. When the indicator stops advancing you've hit TDC. Once you've found TDC, move the indicator dial so the maximum needle reading is set at zero. After setting the dial, turn the crank a few more times to double check your setting, and adjust as necessary.

        Piston stops work fine for finding TDC as well. The slotted bar stop is available from Comp, but will require further slotting to fit the ultra-wide Gen III and IV head-bolt spacing. If you're degreeing with the heads on, the Comp spark plug piston stop is the way to go. We expand on this later.

        You'll need to rotate the crank by a means other than the degree wheel. The degree wheel should be for measuring, not turning. On the Gen III and IV this becomes a little tricky. We fabricated a turning wrench from an old oil pump sprocket cut in half and welded to a shaft. You can get by with a large strap wrench, like those sold at Sears. Comp Cams is working on a socket specific for these engines which will ultimately make life easier.

        Once you've set the indicator dial to TDC, align the degree wheel "0" (0 = TDC) with the tip of the pointer and tighten the balancer bolt. To check our TDC setup, we first rotate the crank until the indicator reads 0.050-inch BTDC. Note the reading on the degree wheel, in our case +11.25 degrees, where BTDC is considered positive or advanced. Next we rotate around until the indicator reads 0.050-inch ATDC. Again, we note the reading on the degree wheel of -11.25 degrees, where ATDC is considered negative or retarded. We should note, the negative and positive nomenclature can be reversed, so long as BTDC and ADTC are decipherable to yourself. We like to match the nomenclature of the timing chain set. To find the center point between these two readings, we simply add them together. -11.25+11.25 = 0 In our case, we're right on with the TDC marker. If you end up with anything other than zero, the wheel must be rotated relative to the crank. If our measurements came up -11.5 and 11.00, we'd end up with -0.5. The wheel would have to be adjusted to even the measurements to -11.25 and 11.25.

        It is necessary to install a lifter on the intake lobe of the first cylinder. In the case of roller lifters, they must remain squarely positioned on the cam so the roller remains parallel with the camshaft. Gen III and IV engines use plastic alignment modules as shown. These are too tight to be used during degreeing because they hold the lifter up off the cam when no spring pressure is applied (this is what allows cams to be swapped with heads on). The lifter should be installed and aligned so the roller is parallel to the cam.

        The indicator jig must be aligned so the measurement tip centers in the lifter pushrod bowl. Once aligned, tighten all the set screws on the indicator jig.

        The indicator is adjusted in the same manner it was for TDC. The engine is rotated while watching the indicator until it reaches a maximum reading corresponding with peak lift. The indicator dial is set to zero at this point. It is good practice to double check the reading a few times to make sure the lifter is moving freely and the alignment of the indicator is true.

        Last edited by jrp; 05-28-2005 at 05:29 AM.
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        Measuring the intake centerline is similar to the procedure used to find TDC. First rotate the crank until the indicator reads 0.050-inch before peak lift. Note the reading on the degree wheel, in our case 66 degrees (at this point, negative and positive don't apply, keep it simple with positive. Other degree wheels may require using negative and positive). Next we rotate around until the indicator reads 0.050-inch after peak lift. Again, we note the reading on the degree wheel of 162 degrees. To find the center point between these two readings, we simply add them together and divide by 2. 66+162 = 228 228 divided by 2 = 114 The intake lobe centerline is set at 114 degrees. This number matches our cam data card packaged with the cam. The cam is degree'd as ground and as specified, and installed with no advance or retard. It is possible for a cam to degree somewhat different than specified, especially in the case of a custom-ground cam. When necessary, the timing set can be adjusted to correct the cam position.

        Degreeing a camshaft when the engine is still in a car or with the cylinder heads installed is generally more time consuming and more difficult. Comp's Sportsman Degree kit, PN 4796, is perfect for in-car or head-on degreeing.

        Locating TDC with the cylinder head on requires a spark plug type piston stop. For Gen III and IV engines (or most any 14mm spark plug head), Comp's PN 4795 unit works fine.

        The piston stop screws in the spark plug hole and the center of the stop is screwed further down into the combustion chamber to provide a stop for the piston. Remember the stop is only for touching the piston, not poking holes in it! Disconnect the battery before even thinking about using these. If the engine is rotated via the starter, you'll either rip threads out of the head or poke a hole in the piston.

        The smaller diameter degree wheel pays dividends when used in the car. The larger wheel simply won't fit.

        Since the Gen III and IV engines use a metric threaded valve cover bolt, you'll need to make a custom fixture mounting stud. A piece of 5/8-inch tubing, some washers and an extra long metric bolt will do the trick if you can't fabricate something.

        The head-on cam fixture mounts using a valve cover bolt hole in the head--pretty slick. It is possible to align the indicator with the lifter, as shown, but it is very difficult to see the contact point between the two.

        The alternative to setting the indicator on the lifter is setting the tip on the valve retainer. First, it is necessary to swap in some light checking springs, so the lifters don't collapse when the engine is rotated. Comp's PN 4758-2 springs do the job. Degreeing is completed the same way as described out of the car with the heads off. A little more patience is required when doing it in the car. Remember to double check all measurements, mistakes are easy to make. And lube up that number one intake lobe now!

        Last edited by jrp; 07-14-2005 at 01:11 AM.
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        Old 07-14-2005, 01:04 AM
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        Default gmblack3 - Guide for Dual Spring Swaps

        Here is my "how to" when I installed crane duals with the crane tool. From what it sounds like the "more performance" tool is different, but this should get you there.

        Instead of grease we used one of those pen magnets to make sure the keepers didn't go anywhere. Sounds like the other guys used grease to keep the keepers in place during reassembly, use the pen magnet when removing the keepers.

        Remove the stock rockers. You can see the rocker here and the broken spring:

        Should look like this when you get all the stock rockers and rail removed:

        Sorry didn't get any pics of the old spring removal. You should be able to figure it out from the install pics.

        Apply 15psi of air to the cylinder where the springs are being removed from. Some say that more should be applied but it worked for us.

        Give a few taps to the valve spring with a dealblow hammer. You just want to make sure that the valve is not going to follow the spring down. If it is let the spring compression tool back up and a few more taps with the hammer on the spring/valve. Once the spring locks are looking free, grab them with a pen style magnet. This is the best way to ensure that you don't drop them. Let the spring tool back up and remove the two springs.

        Then it will look like this:

        If you have some miles on the car, I suggest changing out the valve seals. GM part # 12457652 this is the part # for the brown (exhaust=high-temp) seals. I suggest getting 2 sets (8 in a set) of these. They list at $17.50 a set. There are also seals that are black, they are used for intake seals (not high-temp). They are the same price so you might as well have the higher temp seals (brown) on all 16 valves.

        If you are replacing the springs with aftermarket springs you will need to remove the spring seats. The new springs will need a different valve seats as the aftermarket springs will not sit on the stock valve seats.

        Here is a pic of the stock valve seat being removed. You can also use your pen magnet to remove these as well:

        The valve seals can be removed by using a set of pliers. Careful not to scare the side of the valve when removing the valve seals.

        Grab a new valve seal and lube it with oil on the inside and top, carefully slide it down over the valve. You don't want to damage the seal.

        Slide the 2 new spring seats on and make sure they are flush on the head:

        With a socket and extension tap the valve seal into place. You will feel a click:

        Check again to make sure the spring seats are flush against the head.

        The place the new spring with retainers in place:

        Then get the spring tool and retainers lined up. Start to slowly compress the spring. Make sure the valve does not get caught on the retainer.

        See how the valve is centered in the retainer:

        Here are your spring locks. Notice how one side is bigger. The bigger/thicker side will go up.

        Place them in place like this:

        Slowly release pressure on the spring tool:

        After you remove the tool they should look like this:

        Give a few lite taps again on the spring/valve to make sure that everything is good. Remove the air from that cylinder and move on to the next set of springs.


        Last edited by jrp; 07-14-2005 at 01:12 AM.
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