I'm looking at buying a GM crate vortec ( https://chevroletperforma nceparts.com/p/12530282-5... )which comes with a roller cam, and possibly upgrading the cam to this: https://chevroletperforma nceparts.com/p/hydraulic-...
first, I've read that the OEM cams are not billet and therefore do not require a special distributor gear. can someone verify?Cam Degree equipment / tools
GrumpyVette I've bin reading alot about cam degreeing since i'll be attempting this in the next week or so, I'm pretty sure I can handle the process but wanted to know about the tools used I've read and also watch a video about degreeing a cam but have not found out is it better to use the...garage.grumpysperformance.com
http://www.cranecams.com/userfiles/PP0811A_SinglePages.pdf
secondly, can someone tell me whether, in GM's cam specs, when they say "lobe centerline" are they actually meaning lobe separation angle? for instance, on the cam above the "lobe centerline" is 109°, and the 330 hp flat tappet hydraulic is listed as 112.5° and the 290 hp (also fth) as 114°. I have Grumpyvette's post on LSA/LCL (http://www.chevytalk.org/fusionbb/showpost.php?post/1999489/), so I get the difference. it's just not clear what GM means.[/img]
link too common chevy cams
http://garage.grumpysperformance.co...s-and-a-few-similar-aftermarket.133/#post-163
in MOST articles youll see ,they actually mean lobe separation angle
in almost every catalog or listing,
lobe center angle's can be easily changed
youll need some accurate tools,
like a dial indicator and degree wheel.
http://garage.grumpysperformance.co...ectly-and-get-it-to-last-cam-install-info.90/
http://garage.grumpysperformance.com/index.php?threads/calculating-overlap-and-lsa-or-lca-etc.480/
http://garage.grumpysperformance.com/index.php?threads/cam-gear-and-timing-marks-etc.724/#post-1021
degreeing cam and shifting the lca
I finally got to degree my cam tonight. First cam I've ever done on a build. How far off the cam card timing numbers before most builders would correct with adv/ret? My cam timing numbers were withing 1 to 1.5 degrees and my intake and exhaust C.L. were withing 1/2 a degree...
garage.grumpysperformance.com
LSA =LOBE SEPARATION ANGLE ........LSA is ground into the cam during manufactured, and can,t change,
http://garage.grumpysperformance.co...lsa-effects-your-compression-torque-dcr.1070/
LOBE SEPARATION ANGLE
Above 114 Deg. = Extremely Wide
114-112 Deg. = Wide
112-110 Deg. = Moderately Wide
110-108 Deg. = Moderate
108-106 Deg. = Moderately Tight
106-104 Deg. = Tight
Below 104 Deg. = Extremely Tight
VARYING LOBE SEPARATION ANGLE
Tighten.................................................Widen
Moves Torque to Lower RPM.................Raise Torque to Higher RPM
Increases Maximum Torque..................Reduces Maximum Torque
Narrow Power Band..............................Broadens Power Band
Builds Higher Cylinder Pressure............Reduce Maximum Cylinder Pressure
Increase Chance of Engine Knock.........Decrease Chance of Engine Knock.
Increase Cranking Compression...........Decrease Cranking Compression
Increase Effective Compression............Decrease Effective Compression
Idle Vacuum is Reduced........................Idle Vacuum is Increased
Idle Quality Suffers...............................Idle Quality Improves
Open Valve-Overlap Increases.............Open Valve-Overlap Decreases
Closed Valve-Overlap Increases...........Closed Valve-Overlap Decreases
Natural EGR Effect Increases................Natural EGR Effect is Reduced
Decreases Piston-to-Valve Clearance...Increases Piston-to-Valve Clearance
[color:red]LCA =(LOBE CENTER ANGLES)remember lobe center angles can be changed thru indexing the cam when degreeing it in[/color]
ADVANCING / RETARDING CAM TIMING
KEEP IN MIND MANY CAMS ARE FACTORY SET UP TO BE 4 DEGREES ADVANCED if INSTALLED DOT-TO-DOT
ADVANCING.
Begins Intake Event Sooner........................
Open Intake Valve Sooner..........................
Builds More Low-End Torque.......................
Decrease Piston-Intake Valve Clearance....
Increase Piston-Exhaust Valve Clearance...
RETARDING
Delays Intake Event Closes Intake
Keeps Intake Valve Open Later
Builds More High-End Power
Increase Piston-Intake Valve Clearance
Decrease Piston-Exhaust Valve Clearance
keep in mind theres three basic factors that are interlinked in that each has some effect on how the other two will effect the engines power curve
duration controls the number of degrees of rotation the valve takes from the time it lifts off its seat until it re-seats, the is the TIME the valve will be open and effects the rpm range , the cam will most efficiently operate in.
LIFT, controls the distance the valve opens,and combined with the valve diameter limits the valve curtain, so combined with duration in controls potential flow.
your engine displacement, compression ratrio, potential head flow and header scavengine also will effect the power curve\
LOBE SEPARATION ANGLE will effect how effectively the exhaust can scavenge the cylinders and low rpm reversion pulse strength to some degree thus idle quality, as the period of time while both valves are open at the same time, greatly increases cylinder scavenging.
"Lobe Centerline Angle Determination Chart
To use this chart, first establish the number of cubes in the INDIVIDUAL cylinder, per inch of valve diameter. To get this number, divide the engine displacement by the number of cylinders, then by the intake valve diameter. Find that number on the vertical axis, then move across to the green line. At the intersection point, drop down to the base and read off the LCA required. Because big-block Chevys have angled valves, they need to have about 2 degrees less than this chart indicates."
http://forum.grumpysperformance.com/viewtopic.php?f=52&t=1070
http://forum.grumpysperformance.com/viewtopic.php?f=52&t=480
http://forum.grumpysperformance.com/viewtopic.php?f=52&t=2782&p=7215&hilit=+overlap#p7215
http://forum.grumpysperformance.com/viewtopic.php?f=52&t=90
http://garage.grumpysperformance.co...vs-lsa-lobe-seperation-angle.3816/#post-10147
http://www.hotrod.com/how-to/engine/0607phr-camshaft-basics/
http://forum.grumpysperformance.com/viewtopic.php?f=52&t=2782&p=7433&hilit=+overlap#p7433
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