I have a Crane PowerMax cam #359351. The cam card does not specify the lobe separation angle.

The specs are (@ .050") maximum intake lift at 109* and max exhaust lift is at 119*. Do you add these numbers together then divide by two (which would be 114*)?

Are all lobe separation angles given at .050 lift - or does it not matter?

Duration at 0.50" is 228* intake, and 238* exhaust. Advertised duration (.004" lift) is 290*/300*

Thanks

 

Looks like you found the lobe seperation correctly.


I don't think the lobe seperation is given per say at a certain lift, as its based off the intake and exhaust centerlines max lift in degrees. Then again I am not 100% sure, I haven't spent much time getting that technical with camshaft. later

 

Lobe seperation is measured strictly in degrees and is always constant as the lifter rises from my understanding.

 

Correct.
ICL (Intake Centerline deg ATDC) + ECL (Exhaust Centerline Deg BTDC) / 2 = LSA

Example;
Comp Cams 270S
ICL-106 deg
ECL-114 deg
106+114=220
220/2=110 LSA

Lift is not in the equation.

 

Just to clear up some confusion as to where I picked up the term max lift/duration in order to get lobe seperation. If you look at comps cam specs they list a max lift, below in red.

Part Number: 710511 Grind Number: H-194/250-2S-12

Valve Setting: Intake .000 Exhaust .000 HOT

Lift: Intake @Cam 250 @Valve 400 All Lifts are based
on zero lash and theoretical rocker arm ratios.
Exhaust @ Cam 260 @Valve 416
Rocker Arm Ratio 1.6

Cam Timing: TAPPET @.004
Lift: Opens Closes ADV Duration
Intake 14 BTDC 58 ABDC 252 °
Exhaust 62 BBDC 18 ATDC 260 °

Spring Requirements: Triple Dual Outer Inner
Part Number 99891
Loads Closed 100 LBS @ 1.563 or 1 9/16
Open 219 LBS @ 1.163
Recommended RPM range with matching components
Minimum RPM 1000
Maximum RPM 3500
Valve Float 6500

Cam Timing: TAPPET @.050
Lift:.......Opens ..........Closes ........Max Lift .....Duration
Intake ....(10) ATDC.... 24 ABDC ........107 .........194 °
Exhaust ..38 BBDC .......(16) BTDC ......117 .........202 °



In order to find centerlines you take duration divided by 2 minus int/exh open depends on which one your trying to find.

to find duration you take open + 180 + close = duration () means negative

so in this case -10 + 180 + 24 = 194 is your duration

to find centerline it would be 194 divided by 2 = 97 minus -10 = 107


I assume centerline is what comp is referring too under max lift/degrees as it is 107 if you do the exhaust centerlines it comes out to 117 which is listed under max lift exhaust.

so the lobe seperation is 107 + 117 divided by 2 = 112





Something that would cause some confusion with many people as it did myself, if you look up a compucam and do the math it comes out to something like 109 lsa and is an efi speed density camshaft, I questioned a custom cam grinder and he stated that the lsa of 114 which everyone claims is SD friendly is not necassarily true, as there are many factors involved. So its a rule but there are exceptions.


Something to think about.

 

Good info.
Mike

 

JW, correct.

LSA isn't the only thing to look at. You must look at the duration. If it were a longer duration cam then (bleeding off cylinder pressure) then you would need the increased LSA to salvage some of the manifold vacuum for the SD.

I'm stoping here, this may get to be a loooong discussion. :-)

 

Just what the doctor ordered. Don