I have a pretty much stock motor. Stock cam and heads with tb and intake 19lb injectors. Does it matter which ones I use? I plan on using an e303 cam in the future.
If your setup works with the 1.6 RR then 99% of the time the 1.72 will work fine without any PTV issues. The 1.72 will increase your lift of the cam, so you can use a stock cam and get a bump in HP.
To determine the new lift take the lift on your cam
STOCK - 266*/266* or 212*/212* @.050" and a lift of .445" w/1.6:1 rockers.
.445 /1.6 = .278 . Now take .278 x 1.72 = .478 That is your new lift with the 1.72 RR. Almost the same lift as the E cam. You can keep the stock cam and put the 1.7's on and call it a day if you want.
Specs on the E cam
cam lift.311 int exh .311
valve lift .498 int exh .498
max lift intake 110* exhaust 110*
valve setting. .000 intake exhaust .000
To see what the lift would be with the E cam.
.498/1.6= .312. 312 x 1.7 = .530. Your new lift is .530 with the 1.7's.
IMO, the alphabet cams are not your best choice. They are 20 year old technology and were notorious for being off degree wise from lobe to lobe. I've taken MANY alphabet cams out of the box new and measured the lobes. On every one at least 2 of the lobes were different. I would strongly recommend you go with a custom cam from Ed Curtis, Anderson or Woody. For a little more money you will get a much better cam that you will be very happy with.
If you really stay with the factory cam, the 1.7's would likely be better, because they will effectively make the factory cam bigger. If you plan to get another cam relatively soon, I'd go 1.6 and plan your cam around the 1.6 rockers. I concur that there are better choices than the alphabet cams. By a strange twist of fate, I ended up going with 1.7's recently to get the lift I wanted out of a custom cam, but typically 1.6's are the better choice with a new cam.