Is the lift of the cam the the same amount it lifts the valve off its seat? ie, if the cam has a .500 lift, does that mean the valve is .500 off the seat. I am checking piston to valve clearance.

Add in your rocker ratio.

You take the cam lobe lift times (X) the rocker arm ratio.
Ex: .3506 X 1.5 = .526" valve lift

ok I'm still a little confused. Take my cam ( CB 280H-10). Gross valve lift is .520 (1.7 ratio X Lobe Lift 0.3063). Is that how much the valve lift off the seat is?

Using your example above: The valve moves the 0.520" and the lifter and pushrod move 0.3063".

The rocker arm is just a lever that multiplies the actual cam lift.

BTW 0.520 / 1.7 = 0.3059

[This message has been edited by Wicked 71 (edited June 29, 2005).]

<font face="Arial,Verdana" size="2">Originally posted by Wicked 71:


BTW 0.520 / 1.7 = 0.3059
</font>

Thanks, but let's not get technical over .0004" http://www.nastyz28.com/ubb/wink.gif I took the numbers right off the spec card for the cam. I guess CC didn't want to round up to .521

I got confused about that as well. Then I noticed the card read "gross lift" with a "theoretical rocker ratio = 1.50" They did the math for me. Figured out why I was coming up with answers in the .700-.800 range when shopping for cams.

I want to point one thing out here that most everybody overlooks and that is...

Lift is a secondary power producer when compared to duration!!

You can run very well with a low lift cam that has the duration you want to run AND not have near the valve-train problems that are associated with high lift!! Spring and valve guide interferance and wear problems are three issues here to consider.

AND the roundy-round guys have a whole bunch of low lift race cams to choose from..

I mention this b/c the EXCELLENT, CHEAP, Vortec heads are great but stock are low lift so just use a low lift cam is all!!!

Save some money in the process too....

pdq67