Cams are very different on a Parilla – just one lobe to open both valves. They have a hard time.
This pic has been slightly doctored to enhance the cam profile & show the differences in lift & duration.
The ’54 Fox cam is on the extreme right. No sooner is the valve open than it is shutting again.The 175 Turismo usually has an unmarked cam with a lift of about 5mm & no duration (i.e sharp-topped). This can usefully be changed for an S if you can find one. These have about 6 mm lift & a bit more duration/overlap.
The 175 X1 & SS seem to have the same lift at 7mm but a different profile. The X1 having more duration & a more sudden opening. I
The 250 X1 has even more lift at 8mm, you may notice this cam is from a gear drive engine, the others from chain drive.
This only starts to work at about 5k but produces good power up to about 8.5k.