DSOMZ51

Just got my new cam that was ground to the Spinmonster spec of 230/234, .612XFI/.598XER, 114+2. Out of curiousity, I got out my digitial calipers and measured the lobes from the flattest part of the lobe base to the the highest peak of one of the lobes. I then did the same measurement of my stock LS2 cam and was surprised that my old stock cam measurement was bigger than my new cam. What gives? I certainly would have expected that my new cam lobes would have been longer/taller than my stock cam. I get that the lift, .3520 for the XER lobe, multiplied by the 1.7 rocker ratio gets me the .598 valve lift, and the base circle size comes into play, but how can my new cam lobes be smaller from base to peak than my stock?

5 Liter Eater

Has to be the base circle difference. Measure the back side of the lobe to the casting and measure the peak to the casting and subtract them on both. Or you could put a straight edge across the journals and measure down to the top of the lobe on both to tell the true lift difference.

timd38

That would be my bet!

MyLS1Hauls

Measure across the cam, 90* to the lobe, and then subtract that measurement from the measurement you took across the lobe. Should give you the .352" for the XER lobe. Do the same for the stock cam. You'll see the stock cam lobe lift is lower.

The lobe lift is all relative to the base circle. If all you do is decrease the base circle, then the lobe lift will go up.

DSOMZ51

Thanks to all the helpful replies and suggestions on how to correctly measure with my calipers even though it's not quite the right tool. I was just trying to do somewhat of a "poor man's cam doctor" to somewhat validate my new cam before installing.

My new cam card has a stated intake lobe lift of 0.3600", and an exhaust lobe lift of 0.3520". Trying to carefully measure and aggregate/average multiple readings, I came up with a base circle diameter of 1.4000" and and a total lobe height of 1.7605" for the intake. Subtracting the base circle from the lobe height gives me 0.3605" which is probably as close as I could reasonably expect to qet stated 0.3600" measuring in this manner. For the new cam exhaust lobe, I got 1.7610" - 1.4065" = 0.3545".

For my old stock cam, I cheated a little bit knowing that the cam specs are 204/211 and 0.525"/0.525". Dividing 0.525" by the 1.7 rocker ratio I got a lobe lift of .3088". I measured the base circle of my old cam and got 1.5150" and measured the lobe height and got 1.8250". Thus, 1.8250" - 1.5150" = .3100" which is pretty close to my calculated value of .3088".

I was just concerned that the total lobe height of my old cam was around 1.8250" and my new cam lobe heights between 1.7605" and 1.7615" which were smaller than my old cam. Thanks again everyone!

C6z06man

I'm sure it's the base circle too. Real way is to degree it in an engine. I'm sure what's in the cam card is exactly what you got.