First, welcome! This is your friend for gearing questions
http://www.scriptasylum.com/rc_speed/index.html Try to keep your RPM around 35k...that is what most of us shoot for
Motors....a Tekin 2000, 2200kv would be great on 4s...the 2000kv would be the most efficient...or the 2200kv system you have would work as well. You could gear it high for speed runs with out breaking a sweat.
1. MBX-6 T8 1900KV, RX8 ON 4S
2. MBX-5T 1520, MMM ON 5S
3. MBX-5 ONROAD CONVERSION 1515, MMM ON 5S
4. MRX-3 ON ROAD CONVERSION 1512, MMM ON 6S
5. TEN T 2650 T8, MMP ON 3S