[SuperHart]

When I built my 351W based on a '69 block I went with the Crane 1.7 ratio roller rockers that were offered by Ford Racing and have had absolutely no difficulty with them. My bottom end is box stock, heads are GT-40P iron heads. As long as you are not using 2.02 intake valves AND are keeping the total valve lift WITH 1.7 rockers below .510 according to the techies at Ford Racing there should be no interference problems. I can't say if there was any increase in performance since I never used the 1.6 rockers but I figured a little extra valve lift couldn't hurt anything.

Of course, it is always best to be able to check them out when the motor is on the stand and you can check valve clearance with some clay but I do believe the above information should serve you well. In order to figure out the actual valve lift with the 1.7 rockers you will need to know the advertised valve lift of your cam (usually assumes 1.6 rockers). Set up a ratio consisting of the following: 1.7/1.6 = X/advertised valve lift. Another way to set it up is "advertised lift" x 1.7/1.6 = X. Solve for X which is your valve lift with 1.7 rockers. Therefore, if your advertised valve lift with 1.6 rockers is .442 , it should be .470 with 1.7s. Have fun.