• Camshafts 101

      I wrote this for a Chevy forum I was on, but basic cam info for any engine. All my pics are gone, Ill work on replacing them slowly.

      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.



      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

      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 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.
      This article was originally published in forum thread: Cam write-up, someone sticky this shiz! started by X-Runner View original post
      Comments 15 Comments
      1. X-Runner's Avatar
        X-Runner -
        - 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.


        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

        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
      1. X-Runner's Avatar
        X-Runner -
        - 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 : 115@1.750"

        Open Pressure : 350@1.175"

        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

        *INFO REGARDING CRANE SPRING REVISION* (first batch)



        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
      1. X-Runner's Avatar
        X-Runner -
        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# @ ?

        PP, PRC, TEA, and all other "Gold" springs are all made from the same manufacture; Associated Springs. The differences are in the retainers and seat locators.

        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

        O.D:

        I.D:

        seat pressure: 90 @ 1.800

        open pressure 260 @ ?

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

        O.D

        I.D:

        seat pressure: 90 @ 1.800

        open pressure: 294 @ ?

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

        O.D

        I.D:

        seat pressure: 90 @ 1.800

        open pressure: 294 @ ?

        13. Stock Ls1 Springs

        O.D:

        I.D:

        seat pressure: 75 @ 1.800

        open pressure: 230 @ ?

        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:
      1. X-Runner's Avatar
        X-Runner -
        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.

        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.

        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 LS1.com 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

        from Holly.com

        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):



        1

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



        2

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



        3

        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.
      1. The Yousef's Avatar
        The Yousef -
        stuck.

        good job.
      1. X-Runner's Avatar
        X-Runner -


        4

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



        5

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



        6

        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 most economical route is the LS2 chain pt# 12586482 ordered from SDPC

        - 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

        Stock specs



        Full race cam vs. 3/4 race cam

        Left - full race cam. Center- "standard" cam. Right - 3/4 race cam.





        The info in these links will show you combos Jasper is using to make the different HP and TQ ratings.

        LT1 5.7" 340 HP

        TBI 350" 250 HP

        350" 280 HP

        350" 300 HP

        350" 300 HP Vortex

        350" 325 HP

        350" 350 HP

        350" 360 HP Panther

        TBI 383" 280 HP

        383" 325 HP

        383" 330 HP

        383" 385 HP

        400" 350 HP

        454" 400 HP

        454" 429 HP

        Degreeing a cam...the easy way.

        http://www.cranecams.com/pdf/803.pdf

        Head porting

        http://www.sa-motorsports.com/diyport.aspx

        This will give you your cam options for your engine

        http://www.compcams.com/Technical/CamHelp/

        High Performance Valvetrains

        http://www.aa1car.com/library/perfor...valvetrain.htm

        TBI head flow info

        http://www.thirdgen.org/techboard/tb...-headflow.html
      1. Init2winit's Avatar
        Init2winit -
        So, what exactly is a "3/4" cam, and a "full race" cam? Someone in their 80's must have wrote that part of the article.
      1. X-Runner's Avatar
        X-Runner -
        Quote Originally Posted by Init2winit View Post
        So, what exactly is a "3/4" cam, and a "full race" cam? Someone in their 80's must have wrote that part of the article.
        Look at the difference in the lobes. Holds the valve open longer.
      1. Init2winit's Avatar
        Init2winit -
        Quote Originally Posted by X-Runner View Post
        Look at the difference in the lobes. Holds the valve open longer.
        So, how do you know if one is a 3/4, or a full race cam? Will these cams work with double hump heads, and "pop-ups"?
      1. crafty's Avatar
        crafty -
        I know a Mexican with a convertible civic and a fence post rollcage that had a 3/4 camshaft and that thing wasnt very fast.. I think id go with a fullrace ls1 camshaft in a 2jx motor motor then hose it down with some propane...
      1. 81911SC's Avatar
        81911SC -
        Also you need to look at advertised and actual duration.
        If company A. is saying this is measured at .020" duration, your numbers will be different then the industry standard of .050". Most of the time being a lower number when you measure at .050" then what you wanted.
      1. bloodline's Avatar
        bloodline -
        good write up
      1. jdm eg99's Avatar
        jdm eg99 -
        repped !
      1. Batlground's Avatar
        Batlground -
        Lovely writeup with lots of great info.
      1. Echonova's Avatar
        Echonova -
        Interesting. Tell me more...
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