If you were to swap out a 4120 and put a 4130 in its place without changing anything else, performance would DECREASE.
Take a look at the RPM/Volt ratings for both motors. The 4120/18 has an RPM/Volt rating of 510, while the 4130/16 has an RPM/Volt rating of 390. This means for every Volt applied to the motor, the 4120/18 will turn the prop 510 RPMs faster, while the 4130/16 will only turn it 390 RPMs faster.
If you were to switch to a 4130 from a 4120, you would need to rework the power system, add some cells, and/or use a larger prop.
20 cells and the 4130/16 make for a good .60-size glow powerplant. Just prop for 40 Amps from the tables at
www.modelmotors.cz.