LSA Continued:
So how does one figure out the LSA?
If you know the
Intake Centerline (ICL) and the
Exhaust Centerline (ECL), you can add them together and divide by 2, as follows:
Say you have a 107 ICL and a 117 ECL.
(107+117)/2 =112 LSA.
Keep in mind, that a LSA of 112 does not mean the camshaft will act the same as another camshaft with a LSA of 112. The LSA is determined by different valve opening and closing events, figuring out the ICL and ECL from them, and doing the above math. I will use two typical camshafts below, to show how you cannot compare a camshaft based on the LSA alone. It is just a little piece in the design of a camshaft.
The Ford Racing Z303 camshaft has the following valve events at .050":
Intake Opening: 7* BTDC
Intake Closing: 41* ABDC
Exhaust Opening: 51* BBDC
Exhaust Closing: 3* BTDC
IO+IC+One Stroke = Duration for Intake @ .050"
or 7+41+180 = 228*.
EO+EC+One Stroke = Duration for Exhaust @ .050"
or 51-3+180 = 228*.
Now find the ICL and ECL.
Intake Centerline is found by: (Intake Duration/2) - IO BTDC. In other words...
228/2 = 114. 114-7 =
107* ICL.
Exhaust Centerline is found by: Exhaust Duration/2 + EC BTDC. In other words...
228/2 = 114. 114+3 =
117* ECL.
107+117 = 224/2 =
112* LSA.
Now quickly, one can do this for the Lunati 51014 camshaft. It has the following valve timing specs at .050" and a LSA of 112, like the Z303 camshaft:
Intake Opening: 1* BTDC
Intake Closing: 37* ABDC
Exhaust Opening: 49* BBDC
Exhaust Closing: -3* ATDC
Intake Duration is 1+37+180 = 218*. The ICL is (218/2)-1 =
108*.
Exhaust Duration is 49-3+180 = 226*. The ECL is (226/2)+3 =
116*.
LSA = (108+116)/2 =
112* LSA.
Now you see that both, the Z303 and the Lunati camshaft have the same LSA, but different individual valve events and ICL/ECL figures. So how can a camshaft with the same LSA, act the same, or idle at a particular level?
It cannot because of many different factors and an
endless amount of possibilities.
Overlap Period:
Overlap is close to the same principle of the above LSA information but it is not the same, so do not get it confused. It occurs at the end of the exhaust stroke while the exhaust valve is closing, and when the intake valve is beginning to open when the intake stroke is beginning.
The main goal of the overlap period is exhaust scavenging and can vary depending on power band desired, along with exhaust pieces used on the engine.
More overlap (less/narrow LSA), decreases vacuum, but increases the signal relation between the exiting exhaust and incoming intake air charge. This helps acceleration. However, a camshaft with higher overlap periods will not perform as well at lower RPMS, as compared to one with less RPM.
Less overlap (more/wider LSA), increases vacuum, and helps gas consumption by trapping more gas inside the cylinder, instead of exiting out the exhaust. This helps idle and low RPM quality.
The below calculations will help, but what really effects the period of overlap and how it effects engine characteristics is the combination of the LSA, duration, and lift. LSA is not the only factor in determining the amount of overlap. The more duration and lift on the cam lobes, the larger the overlap area.
You can reduce overlap by reducing duration as well, or having a less aggressive camshaft lobe profile. Just as we have discussed, widening the lobe separation angle reduces overlap as well. The inverse applies.
The intake and exhaust package efficiency, along with how well the incoming air travels over the exiting exhaust and it's valve, help determine what type of overlap can be used for a particular engine combination.
You will see further below, many 5.0L cam specs. It includes a period of overlap for many of the camshafts. This is figured out, like so:
- Add the advertised duration of the intake and exhaust lobes.
- Divide by four.
- Subtract the LSA.
- Multiply by two.
This will give you the period of overlap in reference to the crankshaft degrees.
Here is a calculator to make it easier:
http://www.wallaceracing.com/overlap-calc.php Base Circle:
The base circle of a camshaft is the diameter of the cam lobe that does not have any lift. This is where you set-up your valve train, which is on the base circle. In other words, it is the portion of the path around the cam followed by the rocker arm that doesn't generate lift.
Larger base circles are better for high RPM and higher performing engines. Since a camshaft is turned by the crankshaft, through the connection of the timing chain, it can cause some twist. Most daily driver or street cars do not see any reason to upgrade to a larger base circle, but some serious racers do. There is a lot of stress and pressures on the camshaft from the heavy valve train. A small base circle also creates less wear and does not have as many different lobe profiles as a larger base circle camshaft. Ls1 camshafts have larger base circle camshafts than does a standard 5.0L.
Gross Valve Lift:
This is the most commonly referred to lift number. It is a combination of the lobe lift multiplied by the rocker ratio. In general, the more lift, the more torque that is created. What I seem to have noticed is shorter duration camshafts with high lobe lifts typically are designed for daily driver and street car grinds. It helps torque, throttle response, and overall useable power. The valve train needs to be up to par if you decide to go with large lift numbers. Lift is one of the last factors that effect piston to valve clearance.
Want to know your lift values after a roller rocker change?
Take your current lift numbers and divide it by your current roller rocker ratio. You then get the lift numbers at the lobe. Take your lift number at the lobe and multiply it by the new roller rocker ratio.
Example:
.500" divided by stock 1.6 Roller Rockers = .313"
.313" x by new 1.7 Roller Rockers = .532"
More Roller Rocker Information: Advertised Duration and Duration @ .050":
This camshaft specification is often talked about. Duration is in degrees related to crankshaft revolution. It is the degree the crankshaft is rotated, while the lifter is off the base circle of the camshaft.
A higher duration degree number will do better in the upper RPMS. A lower duration degree number will do better in the low RPMS, all else being the same.
Advertised duration is more of an old school number and is good in marketing. It is typically a measurement from .004", .006", or sometimes .020" up from the base circle. The latter is a better determiner for seeing how a camshaft may act than the preceding .004" and .006" duration measurement marks. With the different variations, it is not an accurate measurement to compare from camshaft to camshaft.
Comp typically uses .006" for the advertised duration.
Crane typically uses .004" for the advertised duration.
This makes the Crane camshafts appear to have a larger camshaft, since they start measuring the duration before Comp. Just be careful, when comparing different camshafts between different companies.
One can figure out if a camshaft has a steeper ramp rate by taking the .050" duration numbers on the cam card and using the advertised duration at the same point. No use in comparing a .004" measurement to a .020" measurement.
Advertised Duration - .050" Duration = Ramp Rate Comparison
Crane 2030: 270-216 = 54
Crane 2031: 276-214 = 62
The Crane 2031 has a milder ramp rate. I used Crane because it is the same company and they compute their advertised duration at .004". A better comparison would be to measure .100" to .050", rather than .050" to .004" measurements, because the latter is lash than anything, which does not translate to the valve because no lift off the base circle has occured yet.
However, there is a more accurate standard of comparison. It is the duration at .050" that is more accurate and widely used. At .050" off the base circle, this is how many degrees the crankshaft turns from .050" on.
It is best to have different duration numbers throughout the lift range to actually begin to compare ramp rates. Watch two camshafts from .006", .050", .100", .200", etc., to get a more accurate idea. A cam doctoring machine does this sort of thing very easily.
This can (but not limited too) help better vacuum, increased throttle response, and a broader power band. The more aggressive ramp rates, lobe profile, acts like a less aggressive camshaft, but creates more "area under the curve," like what a larger base circle camshaft can provide.
Typically longer duration camshafts and longer periods of overlap allow the ability to run a higher static compression ratio without detonation in the low RPM range. Just as well, running with more duration and longer periods of overlap can be a little slow in RPM buildup at lower RPMS.
Advancing and Retarding the Camshaft:
To advance and retard a camshaft you need a multi-index crankshaft sprocket.
Advancing the camshaft:
- Begins the intake valve event to open sooner.
- More low-end power.
- Decreases intake valve clearance.
- Increases exhaust valve clearance.
- Higher compression rating.
Retarding the camshaft:
- Begins the intake valve event to open later.
- More top-end power.
- Increases intake valve clearance.
- Decreases exhaust valve clearance.
- Lower compression gauge reading.
How are camshaft specifications in degrees, measured? Duration - Degrees of
crankshaft rotation.
Valve Opening and Closing Events - Degrees of
crankshaft rotation.
Lobe Centerline - Degrees of
crankshaft rotation from TDC.
Lobe Seperation of Angle - Angle between the intake and exhaust camshaft lobe peaks described in
camshaft degrees.
More Helpful Explanations on Camshafts and Theory: How a Camshaft Works Camshafts Explained Camshafts Explained Camshafts Explained Buddy Rawl's Camshaft Theory Camshaft Question and Answers More Camshaft Question and Answers Become a Camshaft Expert How To Degree a Camshaft Understanding Camshaft Specifications Stock 87-93 Cam Information:
Lift is .444*/.444* - Advertised @ 266*/266* until August of '88, then it went to 276*/266* .
Duration at .050" varies and ranges from 204*+/204*+
85-88:
Lift: .278 intake, .278 exhaust
Duration: 266 intake 266 exhaust
Overlap: 36 degrees, 9.04 factor
Lobe Center: 115 intake, 115 exhaust
89-90:
Lift: .278 intake, .278 exhaust
Duration: 276 intake, 266 exhaust
Overlap: 39 degrees, 19.51 factor
Lobe Center: 116 intake, 115 exhaust
91-95:
Lift: .278 intake, .278 exhaust
Duration: 276 intake, 266 exhaust (.006)
Duration: 214 intake, 210 exhaust (.050)
Overlap: 39 degrees, 19.51 factor
Lobe Center: 116 intake, 115 exhaust
Also have read: 118 intake, 113 exhaust
1.6 Rocker Ratio
Intake Opening: 11* ATDC
Intake Closing: 45* ABDC
Exhaust Opening: 39* BBDC
Exhaust Closing: 9* BTDC
Combustion (0-180) - Exhaust (181-360) - Intake (361-540) - Compression (541-719)
Cam Events at .050":
Intake Opens - 141
Intake at Max Lift - 478
Intake Closes - 585
Exhaust Opens - 141
Exhaust at Max Lift - 246
Exhaust Closes - 351
More Info:
F1ZE-6250-AA cam specs:
Duration 276*/266*
Lift 0.445"/0.445"
LSA 115.5*
ICA 118*
ECA 113*
E5ZE-6250-AA cam specs :
Duration 266*/266*
Lift 0.444"/0.444"
LSA 115*
ICA 116*
ECA 114*
93-95 Cobra:
Lift: .282 intake, .282 exhaust
Duration: 270 intake, 270 exhaust
Overlap: 33.5 degrees, 15.24 factor
Lobe Center: 115 intake, 121.5 exhaust
1985-08/1988
I.O. 17 BTDC / I.C. 69 ABDC
E.O. 67 BBDC / E.C. 19 ATDC
08/1988 - 1993
I.O. 20 BTDC / I.C. 76 ABDC
E.O. 67 BBDC / E.C. 19 ATDC
Cam - Duration @ .050" - Adv. Duration - Valve Lift - Lobe Lift - LSA - Int./Exh. Centerline - Powerband Ford Racing Camshafts B303 - 224*/224* 284*/284* - .480"/.480" - .300"/.300" - 112* - 107* ATDC /117* BTDC - 3,300-5,100 RPM
Overlap: 60 degrees.
1.6 Rocker Ratio
Intake Opening: 5* BTDC
Intake Closing: 39* ABDC
Exhaust Opening: 49* BBDC
Exhaust Closing: 5* BTDC
E303 - 220*/220* - 282*/282* - .498"/.498" - .311"/.311" - 110* - 110*/110* - 2,500-5,500 RPM
Overlap: 62 degrees.
1.6 Rocker Ratio
Intake Opening: 0* BTDC
Intake Closing: 40* ABDC
Exhaust Opening: 40* BBDC
Exhaust Closing: 0* BTDC
F303 - 226*/226* - 288*/288* - .512"/.512" - .320"/.320" - 114* - 109*/119* - 2,800-6,000 RPM
Overlap: 60 degrees.
1.6 Rocker Ratio
Intake Opening: 4* BTDC
Intake Closing: 42* ABDC
Exhaust Opening: 52* BBDC
Exhaust Closing: 6* BTDC
X303 - 224*/224* - 286*/286* - .542"/.542" - .339"/.339" - 112* - 107*/117* - 3,500-6,500 RPM
Overlap: 62 degrees.
1.6 Rocker Ratio
Intake Opening: 5* BTDC
Intake Closing: 39* ABDC
Exhaust Opening: 49* BBDC
Exhaust Closing: 5* BTDC
Z303 - 228*/228* - 290*/290* - .552"/.552" - .345"/.345" - 112* - 107*/117* - Up to 6,500
Overlap: 66 degrees.
1.6 Rocker Ratio
Intake Opening: 7* BTDC
Intake Closing: 41* ABDC
Exhaust Opening: 51* BBDC
Exhaust Closing: 3* BTDC
Trickflow Camshafts TFS 1 - 221*/225* - 275*/279* - .499"/.510" - .312"/.319" - 112* - 108*/116* - 2,000-5,500 RPM
Overlap: 53 degrees.
1.6 Rocker Ratio
Intake Opening: 3* BTDC
Intake Closing: 38* ABDC
Exhaust Opening: 49* BBDC
Exhaust Closing: 4* BTDC
Recommended Valve Springs:
TFS-51400413 with 1.6 ratio rocker arms
Recommended Valve Springs:
TFS-31400414 with 1.7 ratio rocker arms
TFS 2 - 224*/232* - 286*/294* - .542"/.563" - .339"/.352" - 112* - 107*/117* - 2,500-6,000 RPM
Overlap: 66 degrees.
1.6 Rocker Ratio
Intake Opening: 5* BTDC
Intake Closing: 39* ABDC
Exhaust Opening: 53* BBDC
Exhaust Closing: 1* BTDC
Recommended Valve Springs:
TFS-31400414 with 1.6 or 1.7 ratio rocker arms
TFS 3 - 236*/248* - 298*/310* - .574"/.595" - .359"/.372" - 110* - 105*/115* - 3,200-6,800 RPM
Overlap: 84 degrees.
1.6 Rocker Ratio
Intake Opening: 13* BTDC
Intake Closing: 43* ABDC
Exhaust Opening: 59* BBDC
Exhaust Closing: 9* BTDC
Recommended Valve Springs:
TFS-31400414 with 1.6 ratio rocker arms
Steeda Camshafts Steeda #18 - 220*/226* - .480"/.480" - 112* - 2,500-6,000 RPM (N/A or P/A)
Steeda #19 - 220*/226* - 280*/286* - .480"/.480" - .300"/.300" - 115* - 2,500-6,000 RPM
1.6 Roller Rockers
Intake Opening: (1)* ATDC
Intake Closing: 41* ABDC
Exhaust Opening: 52* BBDC
Exhaust Closing: (6)* BTDC
Recommended Valve Springs:
110lbs closed/312 lbs open
Steeda #20 - 224*/230* - .544"/.544" - 112* - Unknown - Stroker or 351 and applied with 1.7 RR's)
Crower Camshafts: Crower 15511 - 218*/224* - .468"/.486" - 114* - 2,200-5,500 RPM
Competition Camshafts Comp XE270HR-12 - 218*/224* - 270*/276* - .544"/.544" - .320"/.320" - 112* - 108*/116* - 1,800-5,800 RPM
Overlap: 49 degrees.
1.7 Roller Rockers
Valve Timing @ .006"
Intake Opening: 27*
Intake Closing: 63*
Exhaust Opening: 74*
Exhaust Closing: 22*
Recommended Valve Springs:
Competition 986-16
Comp XE270HR-14 - 218*/224* - 270*/276* - .512"/.512" - .320"/.320" - 114* - 110*/118* - 1,800-5,800 RPM
Overlap: 45 degrees.
1.6 Roller Rockers
Valve Timing @ .006" (.006" have higher degree numbers than .050" numbers)
Intake Opening: 25*
Intake Closing: 65*
Exhaust Opening: 76*
Exhaust Closing: 20*
Comp XE274HR - 224*/232* - .555"/.565" - 112 - 108*/116*
Lunati Camshafts Lunati 51014 - 218*/226* - 284*/292* - .500"/.510" - .300"/.306" - 112* - 108*/116* - 2,500-6,000 RPM
Overlap: 64 degrees.
1.6 Rocker Ratio
Intake Opening: 1* BTDC
Intake Closing: 37* ABDC
Exhaust Opening: 49* BBDC
Exhaust Closing: -3* ATDC
Recommended Valve Springs:
Part Number: 73100
Cam Information Crane Camshafts Crane 2030 - 216*/220* - 270*/278* - .533"/.544" - .333"/.340" - 112* - 107*/117* - 2,000-5,500 RPM
Overlap: 50 degrees.
1.6 Rocker Ratio
Intake Opening: 1* BTDC
Intake Closing: 35* ABDC
Exhaust Opening: 47* BBDC
Exhaust Closing: (7)* BTDC
Recommended Valve Springs:
Part Number: 99841
Valve Float: 6000 RPM
Crane 2031 - 214*/220* - 276*/282* - .513"/.529" - .302"/.311" - 112* - 107*/117* - 2,000-5,500 RPM
Overlap: 55 degrees.
1.7 Rocker Ratio
Intake Opening: 0* BTDC
Intake Closing: 34* ABDC
Exhaust Opening: 47* BBDC
Exhaust Closing: (7)* BTDC
Recommended Valve Springs:
Part Number: 99841
Valve Float: 6000 RPM
Anderson Ford Motorsport Camshafts - No specs given are guaranteed 100% accurate. AFM B1 - 220*/222* - .490"/.530" - 110* -
AFM B2 - 220*/226* - .529"/.544" - 112* - 108*/116*
1.7 Roller Rocker
AFM B3 - 218*/226* - .542"/.542"
AFM B4 - 224*/232* - 286*/294* - .542"/.563" - .339"/.352" - 112* - 107*/117* - 2,500-6,400 RPM
Overlap: 66 degrees.
1.6 Rocker Ratio
Intake Opening: 5* BTDC
Intake Closing: 39* ABDC
Exhaust Opening: 53* BBDC
Exhaust Closing: (1)* BTDC
Recommended Valve Springs:
10308-1 Springs and Retainer
AFM B-21 - 218*/226* - 272*/280* - .542"/.542" - .320"/.320" - 112* - 108*/116*
Overlap: 52 degrees.
1.7 Rocker Ratio
Intake Opening: 1* BTDC
Intake Closing: 37* ABDC
Exhaust Opening: 49* BBDC
Exhaust Closing: -3* BTDC
AFM B-25 - 218*/226* - 272*/280* - .544"/.544" - .320"/.320"- 112* - 108*/116*
Overlap: 52 degrees.
1.7 Rocker Ratio
Recommended Valve Springs:
130lbs seat - 350lbs open - maximum rpm of 6,200 RPM
AFM B-31 - 218*/228* - 270*/280* - .544"/.544" - 112* - 108*/116*
AFM B-41 - 228*/236* - .544"/.544" - 2,700-6,700 RPM
AFM B-4R - 226*/234* - 294*/302* - .544"/.544" - 112* - 108*/116*- (Renegade Cam)
AFM B451 - 232*/240* 299*/307* - .576"/.576" - .360"/.360" - 112* - 107*/117*
1.6 Rocker Ratio
Intake Opening: 9* BTDC
Intake Closing: 43* ABDC
Exhaust Opening: 57* BBDC
Exhaust Closing: 3* ATDC
AFM B-51 - 2,700-6,700 RPM intended for 351-408 with supercharger.
AFM N2 - Unknown
AFM N3 - 218*/226* - 280*/288* - .542"/.542" - .339"/.339" - 110* - 110*/110* - 2,500-6,000 RPM
Overlap: 64 degrees.
1.6 Rocker Ratio
Intake Opening: (1)* ATDC
Intake Closing: 39* ABDC
Exhaust Opening: 43* BBDC
Exhaust Closing: 3* ATDC
Recommended Valve Spring:
Part Number: 99838
Valve Float: 6,000 RPM
AFM N4 - 222*/230* - .512"/.512"
AFM N6 - Unknown
AFM N-21 - 219*/229* - .512"/.512" - 110* -
AFM N-41 - 222*/232* - 278*/286* - .512"/.512" - .320"/.320" - 110* - 106*/114*
Overlap: 62 degrees.
1.6 Rocker Ratio
Intake Opening: 1* BTDC
Intake Closing: 41* ABDC
Exhaust Opening: 45* BBDC
Exhaust Closing: 5* BTDC
AFM N-412 - 222*/230* - 276*/284* - .512"/.512" - .320"/.320" - 112* - 108*/116*
Intake Opening: 3* BTDC
Intake Closing: 39* ABDC
Exhaust Opening: 51* BBDC
Exhaust Closing: -1* BTDC
AFM N-51P - 228*/238* - .499"/.497" - .312"/.311" - 110* - 106*/114*
AFM N-51HR - 226*/234* - 293*/301* - .520"/.528" - .325"/.330" - 110* - 105*/115*
Overlap: 77 degrees.
1.6 Rocker Ratio
Intake Opening: 8* BTDC
Intake Closing: 38* ABDC
Exhaust Opening: 52* BBDC
Exhaust Closing: 2* BTDC
AFM N-61 - 228*/236* - 280*/288* - .544"/.568" - 340"/355" - 108* - 106*/110*- 2,500-6,500 RPM
AFM N-65 - 226*/234* - .568"/.568" - 110*
1.6 Roller Rocker
AFM N-71 - 232*/240* - .576"/.576" - 110* - 2,700-6,700 RPM
AFM N-81 - 236*/244* - .568"/.576" - 110* - 2,700-6,600 RPM
AFM N-91 - 240*/248* - .576"/.576" - 110* - 106*/114*
1.6 Roller Rocker
Intake Opening: 14* BTDC
Intake Closing: 46* ABDC
Exhaust Opening: 58* BBDC
Exhaust Closing: 10* ATDC
(Valve events not confirmed)
AFM N-111 - 248*/258* - 315*/325* - .576"/.576" - .360"/.360" - 110* - 106*/114* - 2,800-7,000 RPM
Overlap: 100 degrees.
1.6 Rocker Ratio
Intake Opening: 18* BTDC
Intake Closing: 50* ABDC
Exhaust Opening: 63* BBDC
Exhaust Closing: 15* BTDC
AFM N-112 -
AFM N-113 - 270*/278* - 337*/345* - .576"/.576" - .360"/.360" - 104 - 108*/?
1.6 Rocker Ratio
Intake Opening: 31* BTDC
Intake Closing: 59* ABDC
Exhaust Opening: 71* BBDC
Exhaust Closing: 27* BTDC
Holley Kit Cam - 221*/223* - 276*/280* - .509"/.509" - .318"/.318" - 112* - 2,000-6,500 RPM
Possible Lunati cam: LUN-51027LUN).
1.6 Rocker Ratio
Intake Opening: 3.5* BTDC
Intake Closing: 37.5* ABDC
Exhaust Opening: 48.5* BBDC
Exhaust Closing: -5.5* ATDC
Wolverine 1087 - 222*/232* - 299*/309* - .510"/.534" - .319"/.334" - 112* - 107*/117*
Overlap: 80 degrees.
1.6 Rocker Ratio
Intake Opening: 4* BTDC
Intake Closing: 38* ABDC
Exhaust Opening: 53* BBDC
Exhaust Closing: (-1)* ATDC
New part number is Sealed Power ZCS1177R