i was thinking of swiching from 1.5 to 1.6 ratio rocker arms. will the duration change much and will i lose much bottom end(cam is in my sig)?

 

you're going to open a can of worms asking about duration changes when the rocker ratio changes. i'll stick my neck out, sort of, and say yes it changes, but basically it really doesn't and you'd never know it.

 

will i gain much performance? i want to get as much out of the little 283 as i can before i have to swap in a 350

 

direct from comp cams tech guy the last time this was brought up.

hydraulic cam = no change in duration
mechanical = 1* change. because the tip gets to the valve faster. by changing the valve lash on mechanical cams, you change duration somewhat.

 

so should i have more all around with the more agressive valve lift?

also, i have to drill out the pushrod slots to accept the longer rockers, right?

 

Yes, you will have to lengthen the push rod slots to accomodate the shorter rockers.

 

...unless you can get away with using slightly longer push rods without spoiling the valve train geometry. It's really just easiest to slightly elongate the push rod guide holes, or bore them larger and switch to self-aligning rockers or guide plates.

As for the duration change, yes, there is a slight increase in effective duration AT THE VALVE @ 0.075" valve lifts (0.050" lobe lifts - where cams are rated). At the valve is where it really counts, since the assignment of th ecam is to operate the valves. Best-case scenario is a gain of about 2-3° with an already aggressive cam and a lot of ramp. On a relatively mild street or stock cam, you'll get more like 1-2° increase in EFFECTIVE duration, which, as others have mentioned, is really insignificant as far as power is concerned.

BTW - what was the Comp Cams Tech guy's name? I've changed their opinions more than once in the past - why stop now? It's amazing how much you can get out of them if it's a slow day on the phones.