i have a question about reading cam duration. for my curent cam the grind sheet has: SEA duation: 278int 288exh, sae timing: BTC 27, ABC 71, BBC 76, ACT 32. for .050 duration it has 204 int 214 exh.

i'm looking at getting a comp XE262 it has

.006 tappet lift 262int 270exh(these are adv duration right?)

it has valve timing:
at .006 int 25 57
exh 69 21

its .050 duration is 218/224


my question is, is the sea duation and timing the same as the .006 tappet lift duartion and timing? if not how do i swich one or the other to compare them?

on desktop dyno when i put in the timing #s it comes up as for my current cam as 278 288 duration and for the comp 262, 262 270 duration. why does it come up like that? the .050 duarion is more on the comp cam but the adv timing is less and desktop dyno it comes up as less.

 

i put in the .050 specs for my current cam but i don't have the .050 specs for the comp, does anyone have them or know where i can get them?

 

You can look up the grind number and specs on the comp web page.


www.compcams.com

 

Sharp of yu to notice the different way cams are spec'ed by different companies.

SAE duration is not the same as Comp cams "advertized duration" Comp measures their cams at .006" lifter lift.

SAE duration is .004" *valve lift* if I'm not mistakened.

Crane rates theirs at .004" tappet lift and sometimes .0045"'tappet lift.

None of these can be converted one to the other.
There is a cam measureing device called a Cam Doctor that can measure your cam
for duration at any point in the lift curve you specify.
This is the only accurate way to know the seat duration of one cam or another.
Crane Cams always have more advertized duration that Comps
because they are measured at .004" and comp's at .006"

But if you actually measured a cam with the same .050" duration from the two companies you'd find the have much more simular seat duration than the published specs would have you believe.

The actual "running duration" of a cam in a actual running engine is dependent on the lifter bleed down rate at low speed, valve deflection and other things.
The difference between the seat duration and .050" duration
of a cam describes the "hydraulic intensity" of the grind.
But can only be compared if the lift spec is the same.
So your 278/288 cam if measured at .006" may now have a seat duration @.006" of 265 to 270 intake and 275 to 280 exhaust.

I'd be very suspect of a cam with a much smaller seat duration relative to the .050" duration at a known lift spec.
There are definate design limitations that all cam manufacturers
are limited too. Like service life, valvetrain noise, and valvefloat.