Simplify the following text for a Grade 4 native English-speaking person.
Original: Formula Junior was introduced in 1959 , an attempt to be all things to all people ( both a training formula replacing F3 and a high-level international category below F1 replacing F2 ) , and it was soon realized that there was a need to split it into two new formulae ; F2 and F3 were reintroduced for the 1964 season , with F3 requiring one-litre production-based engines ( very similar to FJ in fact ) with very restricted tuning , and F2 also having a 1.0 L engine size , but permitting pure-bred racing engines .
Simplified: F2 and F3 were reintroduced for the 1964 season . F2 cars had a 1.0 L engine .