LCA OR LSA

Grumpy

The Grumpy Grease Monkey mechanical engineer.
Staff member
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?
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

First Id point out that nearly everyone occasionally confuses or at least makes the mistake of using the wrong abbreviation, (LSA, and LCA) these are terms,that are almost, at least in many discussions interchangeable. which they are not.
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\
fe008cfd.gif

porting+valve_area.jpg

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.
EXFLOWZ4.jpg

116_0403_basic_10_z.jpg

LSAChart01x.jpg

"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."

LSA_01.jpg
0810chp_05_z+comp_cams_camshaft_technology_insite_tech+lobe_separation_angle.jpg


116_0403_basic_10_z.jpg


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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Grumpy

The Grumpy Grease Monkey mechanical engineer.
Staff member
OK lets go thru the basics ,
you need an accurate degree wheel,dial indicator etc.
if your one of the millions of guys that generally use the timing gear and the dot-to-dot cam instal methods previously it might amaze you how often that index places the cam several degrees from its intended location

degreeten.png

this adapter comes in really handy to mount the degree wheel and spin the crank,
http://www.summitracing.com/parts/cca-4793
http://www.grumpysperformance.com/
a long bendable stiff wire, like tig welding rod or a heavy gauge coat hanger, to use as a pointer for the degree wheel.
and a piston stop to locate TDC,
a couple lifters, you can epoxy together to use for the dial indicator to read off or ideally this tool
[URL='http://store.summitracing.com/partdetail.asp?autofilter=1&part=PRO%2D66838&N=700+115&autoview=sku']http://store.summitracing.com/partdetai ... toview=sku[/URL]
naturally the dial indicator and a decent magnetic stand will help
youll need a easy way to turn the crank, and the instructions on how to do the process correctly
I generally prefer to start with cams installed STRAIT UP, SPLIT OVERLAP

[URL='http://store.summitracing.com/partdetail.asp?autofilter=1&part=SUM%2DG1056&N=700+115&autoview=sku']http://store.summitracing.com/partdetai ... toview=sku[/URL]

[img]http://www.grumpysperformance.com/
summitracing sells these kits for about $86
[IMG]http://[img]http://www.grumpysperformance.com/sum-g1056_w.jpg
http://www.summitracing.com/parts/sum-g1056
lun-80001_w.jpg


youll need one bushing kit to make corrections

http://www.summitracing.com/parts/cca-4760

YOULL WANT THESE TOOLS LISTED BELOW ALSO[/color]
Ive used mine only a few dozen times but its well worth the money (I previously used two solid lifters I epoxied together on hydraulic or solid lifter flat tappet cams OR a pair of solid roller lifters Id brazed dimes into to measure from on roller cams)
the first time you degree in a cam, you wonder how difficult this COMPLEX PROCEDURE will be, but after doing it MANY DOZENS of TIMES it amazes you that you worried about it the first few times.
555-81625.jpg

MOR-62190.jpg

image_1450.jpg

CCA-4926.jpg

degreewheeladapter.jpg

ctrp_1012_01+race_engine_rebuilding_tips+.jpg

cam_checker1.jpg

camposition.jpg



http://www.summitracing.com/parts/cca-4925
cca-4925.jpg


http://store.summitracing.com/partdetai ... toview=sku

http://www.summitracing.com/parts/sum-900134
sum-900134_w.jpg



http://store.summitracing.com/partdetai ... =PRO-66830
pro-66830_cp.jpg


http://store.summitracing.com/partdetai ... =MOR-61755
http://www.summitracing.com/parts/MOR-61755/
mor-61755_w.jpg

http://www.summitracing.com/parts/MOR-62191/
http://www.totalengineairflow.com/tools

MOR-62191a.jpg

4914r.jpg


THE LONGER I USE THE MOROSO DEGREE WHEEL AND BBC CRANK SOCKET THE MORE IVE COME TO APPRECIATE THEM,, BTW the COMP CAMS SBC VERSION IS BELOW
http://www.summitracing.com/parts/CCA-4 ... refilter=1
cca-4793_cp.jpg

http://store.summitracing.com/partdetai ... toview=sku
ALL THE LINKED THREADS HOLD VERY USEFUL INFO YOULL NEED!
and yeah I know 75% of the guys reading the thread will skip reading the linked info, until
they are forced to research why something went wrong

IT's 25% who bother to take the time, to read links, before they break parts that benefit

http://garage.grumpysperformance.com/index.php?threads/valve-train-clearances-and-problems.528/

http://garage.grumpysperformance.com/index.php?threads/degree-in-that-cam-correctly.27/#post-35

http://garage.grumpysperformance.co...e-springs-and-setting-up-the-valve-train.181/

http://garage.grumpysperformance.co...king-piston-to-valve-clearances.399/#post-488

http://garage.grumpysperformance.com/index.php?threads/valve-seat-angles-and-air-flow.8460/

http://garage.grumpysperformance.com/index.php?threads/calculating-overlap-and-lsa-or-lca-etc.480/

http://garage.grumpysperformance.co...n-the-engine-without-the-starter.79/#post-101

http://garage.grumpysperformance.com/index.php?threads/breaking-in-a-cam.798/#post-1160

http://garage.grumpysperformance.com/index.php?threads/cam-degree-equipment-tools.1759/#post-4440
 
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8

87vette81big

Guest
I have my Eye on purchasing the ISKY Cam degreeing tool soon Grumpy with the plungers for Flat Tappet and Roller Camshafts.
Have Degree wheels, Crank sockets for degree wheel SBC, BBC, PONTIAC V8- BUICK V6-V8, & OLDS V8 & HEMI 426.
Also have the Proform lifter dial indicator billet aluminium stand & many dial indicators.
Also have a Small Crower Degree wheel for in the car - race car cam degreeing checks.
 
8

87vette81big

Guest
Have TDC Finders also.
Head on style & head off style.
 
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