1.6 or 1.7rr on my TFS heads

Need alittle more info on what the engine is.

the higher ratio rocker will increase lift a tad bit.

and in all honesty, i doubt you will notice any differences b/w the two. in my expiereces, ive swapped them, ran both ratios on my stuff and i never felt any real difference.

since the TFS heads are stud mount, rocker adjustments are way easier, so if you want some more lift, and are buying the rockers anways, might as well get 1.7s if you want. if it doesnt cause you any problems. your going to be buying pushrods to center your rocker tip on the the valve anyways. so it doesnt matter what rocker you run. 1.7s might cause PTV issues. you usually gain .030-.040 at max lift depending on the cam's lift starting out. so the gain at lower lift values arent near .030. the low lift during valve overlap is where your piston is most likely to touch the valves. just check clearance like everyone should and make sure all is good. but the TFS state one has some pretty high lift anyways so 1.6s would work just fine also.

when messing with stock style pedestal mount heads, i suggest leaving stock or 1.6s on, putting the higher ratio rockers on stock bolt down style setups throws the rocker geometry off. and the pedestal style setup is alot harder and more a of PITA to adjust properly. they arent just "bolt down and go" like the old myth floating around.

if the pistons have bigger valve reliefs than stock pistons you will probably be alright.

actually the depth of the stock piston notches are enough for most combos. its just the width of the eyebrow isnt enough for the bigger valves the aftermarket heads usually use like 1.94s or 2.02s etc. the valves usually hit the sides of the notches.

plus the TFS TW heads are designed to clear stock pistons, with the canted valves and steeper valve angles. so i doubt you will have any problems, but its always advised to check anyways.

i'm running stock untouched pistons and TW heads with an f-cam and had no PTV issues at all.

1.7s

duration has the biggest affect on PTV issues. but lift will affect it some. the more lift the more open the valve is, i.e. closer to the piston.

your right max lift isnt what your worried about, when the valves are at max lift your pistons is closer to BDC.

but when changing the rocker arm ratio, remeber the duration remains the same on the cam. so the valve is having to open for example .030 farther but in the same amount of time. so what you get is the valve leaving the seat faster and your lift is going to increase through out the whol valve cycle. at the low lift where PTV become and issue, the lift increase at that area is probably less than .010

your duration @ .050 actually increases when going to a higher ratio rocker arm.

honestly if a setup clears with 1.6 rockers. chances are its going to work just fine with 1.7s. if your clearances are so close that a slight increase in rocker arm ratio causes problems then you're too close to begin with.
but still check regardless with YOUR parts. just to say you did.