I got a cam reground to the specs of an Erson RV10 cam, but the machine shop didn't give me a "cam card" telling me the pertinent valve event times. All I know from the machine shop is the following:

Duration @ .050 lift = 212 intake and exhaust
valve lift = .435 intake and exhaust
valve lash is .012 intake and .012 exhaust

I am trying to figure out valve events for purposes of calculating dynamic compression ratio, and I would appreciate it if one of the more knowledgeable beings on this board could double check my math.

According to the Erson catalog, the RV10 cam has the following specs:

Duration = 254
Duration at .050 = 210
Gross lift = .435
Lobe center = 111
Advance = 4 degrees
Valve lash = .022

These are fairly close to what the cam grinder told me, so I will assume that the lobe center and duration figures from the Erson catalog match what I have.

So, a lobe separation of 111 degrees and a common duration of 254 degrees for each lobe equals the following valve events IF the cam was installed "straight up" with 0 degrees advance:

16 degree of lobe overlap ([254/2]-111)
Intake opens at 246 degrees BTDC (254-[16/2])
Intake closes 8 degrees ATDC
Exhaust opens 8 BTDC
Exhaust closes 246 ATDC


Or, calculating these events @.050 lift:

-6 degrees valve overlap ( [(210/2)-111] is that right? no overlap at all?)
Intake opens at 213 degrees BTDC (210-[-3])
Intake closes at 3 BTDC
Exhaust opens at 3 ATDC
Exhaust closes at 213 ATDC

Is that right?

Now I remember why I switched my major from physics to history...

I've just used the advertised duration, numbers, not the lift at 0.050" but you can see how the numbers are built

Hope this helps . . .

_________________
Cheers!
Al T

Yes, it does. Thanks! Looks like if I add the recommended 4 degree advance into my calculations then I got it right. Cool. Good to know I can still do math.