Sometimes, you can get away with it for a while.

It is best to have a non metallic pushrod and have the servo located back from the engine a ways as is practical

2.4 Ghz doesn't seem to be any better than 72 Mhz FM. The RF can get into a servo amplifier and travel to all the servos too

RF sometimes hits when it gets ready too. Maybe everytime you go from left to right down the back straight?