This is my cam. Comp solid roller int lobe RX1718, exh lobe XCX1862
Int duration states 285, specs show 284 according to open/close on the card, measures 287. Maybe the opening ramp is ??? TDC has been verified. Measurements taken at the lifter. Which measurements are correct? Obviously not all of them. This cam has been in the motor for 500 passes where it is now. It does have a Jessel and plenty of clearance in both directions. So moving it after install is an option. 572, 15-1, ported Indy -1, Indy 440-25 cross ram, 2 edelbrock 750. 3345lbs normally runs 9.1x@146 best of 9.04@149. Where would you put it?
Doug
intake
Card
duration 285 open 30 BTDC close 74 ABDC 112 C/l
Actual readings
open 35 BTDC close 72 ABDC 108.5 C/L
4 advance 2 advance 3.5 advance

exhaust
Card
open 78 BBDC close 34 ATDC 112 C/L
Actual readings
open 76 BBDC close 32 ATDC 116.5 C/L
2 advance 2 advance 4.5 advance

Use the actual readings. The card assumes a specific size of roller wheel so the actual reading can be different if you are using a different roller.

But which actual reading? open, close, or C/L. They all result in a different installed C/L
Doug

To be certain you have it at your chosen centerline, I would check at .050 lobe lift on both sides of the intake lobe and figure from there. I would guess 108 would be a good place to run it, unless someone you trust advises different. I run mine at 110, but i have only 3065 weight and actual 6200 stall as well as a torqueflite. My cam is 285/ 296/ 114 ,.870 gross int lift

Yes

It affects the readings just like a different rocker arm ratio does

I check the intake lobe center first at .200,.100 and at .050 before and after max lift, once I get the intake lobe where I want it(sometimes I'll see three different results like 108,107 and 106) I then check the exhaust lobe in the same three places to make sure that cam is ground on the LSA the card says
I have sent more than one cam back due to too much differences on the lobes
As far as installed LSA with 500 runs on it now what do you need to make better, upper RPM performance or better bottom end?

I have always used .050 before and after max lift.

I have a cam that the numbers don't sync exactly but I figure it's pushrod flex and angle deflection. I use light springs but indy heads pushrods are not the straightest

The heads are not installed. What it appears to me is the intake lobe is actually 287@.050, not 285. The change occurs at the intake opening point. It's 2 degrees earlier than the card calls out. This then moves the int C/L to 110.5. The exh open/close are at the correct 112 C/L giving a 111.25 LCA. It also appears the exh lobe is assemetrical rendering the measurement at max lift for C/L useless .
Doug

That is why i figure the best way is to check both sides of the intake lobe at .050. The .050 readings are really all you can go by since thats all that is on the card.

Like Greg.. I use the .050 before and after..
that way I can see if the cam or the cam card
are off.. I go off the lifter itself

I think most grinders rate the lobe based on a .750" o.d. wheel...your are likely .8 or even .825"

I called Comp. "A few degrees extra duration isn't unusual" was their reply.
Doug

If it's a symmetrical lobe, base it on the max lift point.

Someone else mentioned .050 before and after max lift point. Good method and doesn't require a lot crank turning.

I like having a bunch of info on the cam, so I usually measure the duration at 0.002", 0.004", 0.006", 0.008", 0.010", 0.020", 0.050", 0.100", 0.150", 0.200", 0.250", 0.300", and 0.050" above to max lift. For double check of centerline, I might add a few points around either side of max lift.
I just plug the numbers into a spread sheet and usually the centerline numbers are pretty close.
Here is what I had for the Comp 286 HR hydraulic roller cam:
Lobe Opening Lift: Crank Degrees Lobe Closing Lift: Crank Degrees CENTERLINE DURATION LIFT @ 1.6:1
0.002 42.0000 BTDC 0.002 260.0000 ATDC 109.00 302.0 0.0032
0.004 39.0000 BTDC 0.004 255.0000 ATDC 108.00 294.0 0.0064
0.006 36.0000 BTDC 0.006 252.0000 ATDC 108.00 288.0 0.0096
0.008 34.0000 BTDC 0.008 250.0000 ATDC 108.00 284.0 0.0128
0.010 32.0000 BTDC 0.010 248.0000 ATDC 108.00 280.0 0.0160
0.015 28.0000 BTDC 0.015 244.0000 ATDC 108.00 272.0 0.0240
0.020 25.0000 BTDC 0.020 241.0000 ATDC 108.00 266.0 0.0320
0.030 19.5000 BTDC 0.030 236.0000 ATDC 108.25 255.5 0.0480
0.040 15.0000 BTDC 0.040 231.0000 ATDC 108.00 246.0 0.0640
0.050 11.5000 BTDC 0.050 228.0000 ATDC 108.25 239.5 0.0800
0.100 3.0000 ATDC 0.100 213.0000 ATDC 108.00 216.0 0.1600
0.150 15.0000 ATDC 0.150 201.0000 ATDC 108.00 186.0 0.2400
0.200 27.0000 ATDC 0.200 189.0000 ATDC 108.00 162.0 0.3200
0.250 40.5000 ATDC 0.250 175.0000 ATDC 107.75 134.5 0.4000
0.300 58.0000 ATDC 0.300 158.0000 ATDC 108.00 100.0 0.4800
0.350 85.0000 ATDC 0.350 130.0000 ATDC 107.50 45.0 0.5600
0.360 98.0000 ATDC 0.360 119.0000 ATDC 108.50 21.0 0.5760

Count me in the .050 before and after crowd...AS pointed out manufactures numbers will vary as will the parts used for those measurements. So always found this method to work best. Amazing what you find checking stuff though. Always love checking lift etc as actual numbers as well once the valvetrain is set up. Many would be surprised how much they change.

The intake closing point and the exhaust open close are true to the card. The intake opening point is 2 degrees early. The cam does have 2 degrees more intake duration than the card states. Verified by checking at .020",.050",.200" on both #1 and #6 cylinders. I agree using the open/close points for set-up is the way to go. Its all just a baseline anyway. Never really know what it likes unless you change it. However with the extra intake duration I may try loosening the intake lash and see what happens. Long block is done. I'll be testing by the end of the month.
Doug

I like the Max lift point to degree the cam, it is Also the Max flow point. But either way you do it, it is just a starting reference point.

But I care more about the "max flow event" then the opening and closing events on any cam. Degree for max lift on a centerline of choice and Don't worry about the opening and closing events on said duration cam.